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A polybenzimidazole polymer supports the formation of gold nanoparticles with well-defined sizes on graphene.
Credit: International Institute for Carbon-Neutral Energy Research (I²CNER), Kyushu University

Research group develops new method for creating highly efficient gold nanoparticle catalysts for fuel cells

The successful future of fuel cells relies on improving the performance of the catalysts they use. Gold nanoparticles have been cited as an ideal solution, but creating a uniform, useful catalyst has proven elusive. However, a team of researchers at Kyushu University’s International Institute for Carbon-Neutral Energy Research (I2CNER) devised a method for using a new type of catalyst support.

In a potential breakthrough technology for fuel cells, a recently published article in Scientific Reports shows how wrapping a graphene support in a specially prepared polymer provides an ideal foundation for making uniform, highly active gold nanoparticle catalysts.

Fuel cells produce electricity directly from the separate oxidation of the fuel and the reduction of oxygen. The only by-product of the process is water, as fuel cells produce no greenhouse gases and are widely seen as essential for a clean-energy future.

However, the rate at which electricity can be produced in fuel cells is limited, especially by the oxygen reduction reaction (ORR), which must be catalyzed in practical applications. Although current platinum-based catalysts accelerate the reaction, their unhelpful propensity to also catalyze other reactions, and their sensitivity to poisoning by the reactants, limits their overall utility. Despite bulk gold being chemically inert, gold nanoparticles are surprisingly effective at catalyzing the oxygen reduction reaction without the drawbacks associated with their platinum counterparts.

Nevertheless, actually creating uniformly sized gold nanoparticle catalysts has proven problematic. Previous fabrication methods have produced catalysts with nanoparticle sizes that were too large or too widely distributed for practical use. Meanwhile, efforts to regulate the particle size tended to restrict the gold’s activity or make less-stable catalysts.

“Creating small, well-controlled particles meant that we needed to focus on particle nucleation and particle growth,” lead and corresponding author Tsuyohiko Fujigaya says. “By wrapping the support in the polybenzimidazole polymer we successfully developed with platinum, we created a much better support environment for the gold nanoparticles.”

The team also tested the performance of these novel catalyst structures. Their catalysts had the lowest overpotential ever reported for this type of reaction. “The overpotential is a bit like the size of the spark you need to start a fire,” coauthor Naotoshi Nakashima says. “Although we’re obviously pleased with the catalysts’ uniformity, the performance results show this really could be a leap forward for the ORR reaction and maybe fuel cells as well.”

The article “Growth and Deposition of Au Nanoclusters on Polymer-wrapped Graphene and Their Oxygen Reduction Activity” was published in Scientific Reports.


Story Source:

The above post is reprinted from materials provided by Kyushu University, I2CNER. Note: Materials may be edited for content and length.


Journal Reference:

  1. Tsuyohiko Fujigaya, ChaeRin Kim, Yuki Hamasaki, Naotoshi Nakashima. Growth and Deposition of Au Nanoclusters on Polymer-wrapped Graphene and Their Oxygen Reduction Activity. Scientific Reports, 2016; 6: 21314 DOI:10.1038/srep21314

A study conducted by the Solar Energy Industries Association (SEIA) indicates 2016 will be a banner year for U.S. solar installations.

The non-profit based in Washington D.C. predicts an estimated 119 percent increase this year due to tax incentives and price reductions.

First, Congress extended a 30 percent federal Investment Tax Credit for all different types of solar projects through 2019. Plus, the price of panels has dropped by 67 percent since 2010, according to the report.

SEIA’s investigation notes demand will grow in residential and commercial markets, but utility-scale installations will encompass 74 percent of the installations for 2016.

These factors could make solar installations an intriguing option for homeowners and businesses. Whole Foods agreed to a partnership with Solar City in which the alternative energy company will retrofit rooftop solar panels on 100 stores.

Fortune adds that electricity companies have nothing to worry about because solar energy only accounts for 1 percent of the nation’s power output.

By 2020, SEIA predicts solar power will grow to 3.5 percent.

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*** From the World Economic Forum (WEF)

Five videos to watch on International Women’s Day

As we celebrate International Women’s Day on 8 March, here are five videos that highlight the struggle for gender parity.

I. The Global Gender Gap Report

The Global Gender Gap Index ranks over 140 economies according to how well they are leveraging their female talent pool, based on economic, educational, health-based and political indicators. With a decade of data, the 2015 edition of the Global Gender Gap Report– first published in 2006 – reveals patterns of change around the world.

II. Davos 2016 – Progress Towards Parity

At the Annual Meeting 2016 in Davos, an all-star panel gathered to discuss the challenges facing the journey towards gender parity. What are the opportunities to achieve progress towards parity as the demand on workforces and societies rapidly shift?

Panelists:
· Melinda Gates, Co-Chair, Bill & Melinda Gates Foundation, USA.
· Jonas Prising, Chairman and Chief Executive Officer, ManpowerGroup, USA.
· Sheryl Sandberg, Chief Operating Officer and Member of the Board, Facebook, USA.
· Justin Trudeau, Prime Minister of Canada.
· Zhang Xin, Chief Executive Officer and Co-Founder, SOHO China, People’s Republic of China.

III. China 2015 – Parity Equals Performance

Moderated by Joe Palca, Science Correspondent at NPR, this session held at the Annual Meeting of the New Champions 2015 in Dalian, People’s Republic of China, addresses the gender gap in science and technology. Are companies missing out on female-led innovation in the digital economy?

Panelists include:
– Masako Egawa, Professor, Hitotsubashi University, Japan; Global Agenda Council on Japan
– Maria Pinelli, Global Vice-Chair, Strategic Growth Markets, EY, United Kingdom
– Jun Qin, Chairman, Tsinghua Holding Technological Innovation Co., People’s Republic of China; Young Global Leader
– Nina Tandon, President and Chief Executive Officer, EpiBone, USA

IV. Emma Watson

UN Women Goodwill Ambassador, Emma Watson, delivered a stirring speech encouraging world and corporate leaders to take action for gender equality during the kickoff of a HeForShe programme launch during the World Economic Forum Annual Meeting in Davos on January 23rd, 2015.

V. Davos 2016: The Gender Impact on the Fourth Industrial Revolution

This issue briefing examined the degree and breadth of gender gaps across key industries and possible remedies to consider for each.
Speakers: – Mara Swan, Executive Vice-President, Global Strategy and Talent, ManpowerGroup, USA. – Theresa Whitmarsh, Executive Director, Washington State Investment Board, USA. – Saadia Zahidi, Head of Employment and Gender Initiatives, Member of the Executive Committee, World Economic Forum.

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Smokestack Emissions Nano Carbon Capture id42759

“Our climate change solution is two fold: To transform the greenhouse gas carbon dioxide into valuable products and to provide greenhouse gas emission-free alternatives to today’s industrial and transportation fossil fuel processes,” Stuart Licht, professor of chemistry at George Washington University

An interdisciplinary team of scientists has worked out a way to make electric vehicles that are not only carbon neutral, but carbon negative, capable of actually reducing the amount of atmospheric carbon dioxide as they operate. They have done so by demonstrating how the graphite electrodes used in the lithium-ion batteries that power electric automobiles can be replaced with carbon material recovered from the atmosphere.

The recipe for converting carbon dioxide gas into batteries is described in a paper published in the March 2 issue of the journal ACS Central Science (“Carbon Nanotubes Produced from Ambient Carbon Dioxide for Environmentally Sustainable Lithium-Ion and Sodium-Ion Battery Anodes”).

Converting Carbon Dioxide into BatteriesThe Solar Thermal Electrochemical Process (STEP) converts atmospheric carbon dioxide into carbon nanotubes that can be used in advanced batteries. (Image: Julie Turner, Vanderbilt University)

“Our climate change solution is two fold: To transform the greenhouse gas carbon dioxide into valuable products and to provide greenhouse gas emission-free alternatives to today’s industrial and transportation fossil fuel processes,” Stuart Licht, professor of chemistry at George Washington University said.

“In addition to better batteries other applications for the carbon nanotubes include carbon composites for strong, lightweight construction materials, sports equipment and car, truck and airplane bodies.” The unusual pairing of carbon dioxide conversion and advanced battery technology is the result of a collaboration between Dr. Licht, and the laboratory of assistant professor of mechanical engineering Cary Pint at Vanderbilt University. Licht adapted the lab’s solar thermal electrochemical process (STEP) so that it produces carbon nanotubes from carbon dioxide and with Pint by incorporating them into both lithium-ion batteries like those used in electric vehicles and electronic devices and low-cost sodium-ion batteries under development for large-scale applications, such as the electric grid. In lithium-ion batteries, the nanotubes replace the carbon anode used in commercial batteries.

The team demonstrated that the carbon nanotubes gave a small boost to the performance, which was amplified when the battery was charged quickly. In sodium-ion batteries, the researchers found that small defects in the carbon, which can be tuned by STEP, can unlock stable storage performance over 3.5 times above that of sodium-ion batteries with graphite electrodes. Most importantly, both carbon-nanotube batteries were exposed to about 2.5 months of continuous charging and discharging and showed no sign of fatigue.

Published on Feb 25, 2016: Video interview with Cary Pint explaining this research.

Scientists from Vanderbilt and George Washington universities have worked out a way to make electric vehicles not just carbon neutral but carbon negative by demonstrating how the graphite electrodes used in the lithium-ion batteries can be replaced with carbon recovered from the atmosphere.

“This trailblazing research has achieved yet another amazing milestone with the incorporation of the carbon nanotubes produced by Stuart Licht’s STEP reduction of carbon dioxide process into batteries for electric vehicles and large scale storage,” said Michael King, chair of GW’s Department of Chemistry. “We are thrilled by this translation of basic research into potentially useful consumer products while mitigating atmospheric carbon dioxide buildup. This is a win-win for everyone!”
The researchers estimate that with a battery cost of $325 per kWh (the average cost of lithium-ion batteries reported by the Department of Energy in 2013), a kilogram of carbon dioxide has a value of about $18 as a battery material – six times more than when it is converted to methanol – a number that only increases when moving from large batteries used in electric vehicles to the smaller batteries used in electronics.

And unlike methanol, combining batteries with solar cells provides renewable power with zero greenhouse emissions, which is needed to put an end to the current carbon cycle that threatens future global sustainability.

Licht also proposes a modified flue system for combustion plants that incorporates this process could be self-sustaining, as exemplified by a new natural gas power plant with zero carbon dioxide emissions. That’s because the side product of the process is pure oxygen, which plants could then use for further combustion. The calculated total cost per metric tonne of CNTs would be much less expensive than current synthetic methods.
“This approach not only produces better batteries but it also establishes a value for carbon dioxide recovered from the atmosphere that is associated with the end-user battery cost unlike most efforts to reuse CO2 that are aimed at low-valued fuels, like methanol, that cannot justify the cost required to produce them,” said Pint.
Source: Vanderbilt University

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collage of green nature landscape with planet Earth above it

A ‘Green-er’ Clean Energy Earth?

In the latest edition of their annual letter published today, Bill and Melinda Gates argue that the world needs “an energy miracle,” and are willing to bet that such a breakthrough will arrive within 15 years.

 

Bill Gates cites scientists’ estimates that to avoid the worst effects of climate change the biggest carbon-emitting countries must reduce greenhouse gas emissions by 80% by 2050, and the world must more or less stop such emissions entirely by 2100. And that’s not going to happen if we continue on our current trajectory.

You can see Gates explain the equation in the Quartz video above.

Gates says he was stunned to discover how little research and development money is going toward breakthroughs in cheaper, scaleable clean-energy sources.Gates announced last year that he was committing $1 billion of his own money over five years to invest in clean-energy technology, and has been pushing governments to increase their funding.

To explain the need for a breakthrough in energy technology, he uses an equation (similar to the Kaya identity equation) that represents the factors determining how much carbon dioxide the world emits every year.

“Within the next 15 years, I expect the world will discover a clean-energy breakthrough that will save our planet and power our world.” Gates believes that cleaner options such as electric cars and LED lighting won’t bring down energy consumption enough to hit those climate-change goals. In fact, he doesn’t see any current clean-energy technology that will enable the world to eliminate carbon dioxide emissions by 2100, partly because it’s not consistent or inexpensive enough.

 

Gates has personally invested in next-generation nuclear power technology, which he describes as “a very promising path.” He is also backing efforts to improve battery technology, so that energy from intermittent clean sources such as solar and wind can be stored affordably at large scale for use over time. “I think we need to pursue many different paths,” says Gates in an interview with Quartz.

 

And he’s betting on relatively fast progress. “Within the next 15 years,” Gates predicts in his letter, “I expect the world will discover a clean-energy breakthrough that will save our planet and power our world.”

** Re-Posted from the World Economic Forum

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Seawater Hydo GoPro rd1602_ocean

GoPro-Funded Startup’s Tech Turns Seawater into Hydrogen

Joi Scientific held a forum on Tuesday at its Kennedy Space Center-based headquarters in Florida to discuss its technology that can convert saltwater into a hydrogen power source.

Founder and CEO Traver Kennedy didn’t elaborate on the specific procedure his technology uses to create hydrogen,writes Fortune.  He told the audience the process would be similar to something that “happens in nature,” but could potentially produce “hydrogen on demand” whenever a customer wants it.

A successful launch of Joi’s technology could create a new paradigm for energy innovation. Scientists have concluded that the extraction process of transforming hydrogen into water can be expensive and take up a considerable amount of energy, but Joi said his technology’s process would be different,reports the Orlando Sentinel.

The company recently raised a $5M investment from the Woodman Family Trust, a fund led by Dean Woodman. He’s the father of Nick Woodman, founder and CEO of popular camera provider GoPro. 

Joi will use the money to kick-start the commercialization process, reports Fortune. Kennedy told the publication he started discussions with manufacturers a year ago about licensing agreements to help these partners “incorporate it into their gear to make hydrogen to power fuel cells, burners, and boilers.”

Kennedy plans on installing his technology into a few projects later this year.

Lithium Batt Metal 23d9926Rechargeable lithium metal batteries have been known for four decades to offer energy storage capabilities far superior to today’s workhorse lithium-ion technology that powers our smartphones and laptops. But these batteries are not in common use today because, when recharged, they spontaneously grow treelike bumps called dendrites on the surface of the negative electrode.

Over many hours of operation, these dendrites grow to span the space between the negative and positive electrode, causing short-circuiting and a potential safety hazard.

Current technology focuses on managing these dendrites by putting up a mechanically strong barrier, normally a ceramic separator, between the negative and the positive electrodes to restrict the movement of the dendrite. The relative non-conductivity and brittleness of such barriers, however, means the battery must be operated at high temperature and are prone to failure when the barrier cracks.

But a Cornell team, led by chemical and biomolecular engineering professor Lynden Archer and graduate student Snehashis Choudhury, proposed in a recent study that by designing nanostructured membranes with pore dimensions below a critical value, it is possible to stop growth of dendrites in lithium batteries at room temperature.

“The problem with ceramics is that this brute-force solution compromises conductivity,” said Archer, the William C. Hooey Director and James A. Friend Family Distinguished Professor of Engineering and director of the Robert Frederick Smith School of Chemical and Biomolecular Engineering.

“This means that batteries that use ceramics must be operated at very high temperatures — 300 to 400 degrees Celsius [572 to 752 degrees Fahrenheit], in some cases,” Archer said. “And the obvious challenge that brings is, how do I put that in my iPhone?”

You don’t, of course, but with the technology that the Archer group has put forth, creating a highly efficient lithium metal battery for a cellphone or other device could be reality in the not-too-distant future.

Archer credits Choudhury with identifying the polymer polyethylene oxide as particularly promising. The idea was to take advantage of “hairy” nanoparticles, created by grafting polyethylene oxide onto silica to form nanoscale organic hybrid materials (NOHMs), materials Archer and his colleagues have been studying for several years, to create nanoporous membranes.

To screen out dendrites, the nanoparticle-tethered PEO is cross-linked with another polymer, polypropylene oxide, to yield mechanically robust membranes that are easily infiltrated with liquid electrolytes. This produces structures with good conductivity at room temperature while still preventing dendrite growth.

“Instead of a ‘wall’ to block the dendrites’ proliferation, the membranes provided a porous media through which the ions pass, with the pore-gaps being small enough to restrict dendrite penetration,” Choudhury said. “With this nanostructured electrolyte, we have created materials with good mechanical strength and good ionic conductivity at room temperature.”

Archer’s group plotted the performance of its crosslinked nanoparticles against other materials from previously published work and determined “with this membrane design, we are able to suppress dendrite growth more efficiently that anything else in the field. That’s a major accomplishment,” Archer said.

One of the best things about this discovery, Archer said, is that it’s a “drop-in solution,” meaning battery technology wouldn’t have to be radically altered to incorporate it.

“The membrane can be incorporated with batteries in a variety of form factors, since it’s like a paint — and we can paint the surface of electrodes of any shape,” Choudhury added.

This solution also opens the door for other applications, Archer said.

“The structures that Snehashis has created can be as effective with batteries based on other metals, such as sodium and aluminum, that are more earth-abundant and less expensive than lithium and also limited by dendrites,” Archer said.

The group’s paper, “A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles,” was published Dec. 4 in Nature Communications. All four group members, including doctoral students Rahul Mangal and Akanksha Agrawal, contributed to the paper.

The Archer group’s work was supported by the National Science Foundation’s Division of Materials Research and by a grant from the King Abdullah University of Science and Technology in Saudi Arabia. The research made use of the Cornell High Energy Synchrotron Source, which also is supported by the NSF.


Story Source:

The above post is reprinted from materials provided by Cornell University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Snehashis Choudhury, Rahul Mangal, Akanksha Agrawal, Lynden A. Archer. A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles. Nature Communications, 2015; 6: 10101 DOI: 10.1038/ncomms10101

Lithium Batt Micro Org 160204151102_1_540x360Lithium Battery Catalyst Found to Harm Key Soil Microorganism

University of Wisconsin-Madison

The material at the heart of the lithium ion batteries that power electric vehicles, laptop computers and smartphones has been shown to impair a key soil bacterium, according to new research published online in the journal Chemistry of Materials.

The study by researchers at the University of Wisconsin-Madison and the University of Minnesota is an early signal that the growing use of the new nanoscale materials used in the rechargeable batteries that power portable electronics and electric and hybrid vehicles may have untold environmental consequences.

Researchers led by UW-Madison chemistry Professor Robert J. Hamers explored the effects of the compound nickel manganese cobalt oxide (NMC), an emerging material manufactured in the form of nanoparticles that is being rapidly incorporated into lithium ion battery technology, on the common soil and sediment bacterium Shewanella oneidensis.

Lithium Batt Micro Org 160204151102_1_540x360

Shewanella oneidensis is a ubiquitous, globally distributed soil bacterium. In nature, the microbe thrives on metal ions, converting them to metals like iron that serve as nutrients for other microbes. The bacterium was shown to be harmed by the compound nickel manganese cobalt oxide, which is produced in nanoparticle form and is the material poised to become the dominant material in the lithium ion batteries that will power portable electronics and electric vehicles.
Credit: Illustration by Marushchenko/University of Minnesota

“As far as we know, this is the first study that’s looked at the environmental impact of these materials,” says Hamers, who collaborated with the laboratories of University of Minnesota chemist Christy Haynes and UW-Madison soil scientist Joel Pedersen to perform the new work.

NMC and other mixed metal oxides manufactured at the nanoscale are poised to become the dominant materials used to store energy for portable electronics and electric vehicles. The materials, notes Hamers, are cheap and effective.

“Nickel is dirt cheap. It’s pretty good at energy storage. It is also toxic. So is cobalt,” Hamers says of the components of the metal compound that, when made in the form of nanoparticles, becomes an efficient cathode material in a battery, and one that recharges much more efficiently than a conventional battery due to its nanoscale properties.

Hamers, Haynes and Pedersen tested the effects of NMC on a hardy soil bacterium known for its ability to convert metal ions to nutrients. Ubiquitous in the environment and found worldwide, Shewanella oneidensis, says Haynes, is “particularly relevant for studies of potentially metal-releasing engineered nanomaterials. You can imagine Shewanella both as a toxicity indicator species and as a potential bioremediator.”

Subjected to the particles released by degrading NMC, the bacterium exhibited inhibited growth and respiration. “At the nanoscale, NMC dissolves incongruently,” says Haynes, releasing more nickel and cobalt than manganese. “We want to dig into this further and figure out how these ions impact bacterial gene expression, but that work is still underway.”

Haynes adds that “it is not reasonable to generalize the results from one bacterial strain to an entire ecosystem, but this may be the first ‘red flag’ that leads us to consider this more broadly.”

The group, which conducted the study under the auspices of the National Science Foundation-funded Center for Sustainable Nanotechnology at UW-Madison, also plans to study the effects of NMC on higher organisms.

According to Hamers, the big challenge will be keeping old lithium ion batteries out of landfills, where they will ultimately break down and may release their constituent materials into the environment.

“There is a really good national infrastructure for recycling lead batteries,” he says. “However, as we move toward these cheaper materials there is no longer a strong economic force for recycling. But even if the economic drivers are such that you can use these new engineered materials, the idea is to keep them out of the landfills. There is going to be 75 to 80 pounds of these mixed metal oxides in the cathodes of an electric vehicle.”

Hamers argues that there are ways for industry to minimize the potential environmental effects of useful materials such as coatings, “the M&M strategy,” but the ultimate goal is to design new environmentally benign materials that are just as technologically effective.


Story Source:

The above post is reprinted from materials provided by University of Wisconsin-Madison. The original item was written by Terry Devitt. Note: Materials may be edited for content and length.


Journal Reference:

  1. Mimi N. Hang, Ian L. Gunsolus, Hunter Wayland, Eric S Melby, Arielle C. Mensch, Katie R Hurley, Joel A. Pedersen, Christy L. Haynes, Robert J Hamers. Impact of Nanoscale Lithium Nickel Manganese Cobalt Oxide (NMC) on the Bacterium Shewanella oneidensis MR-1. Chemistry of Materials, 2016; DOI: 10.1021/acs.chemmater.5b04505

 

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Nanowires 020316 bf8802f7297fd2bfea985c26d0b9a636_w1440

California is committed to 33 percent energy from renewable resources by 2020. With that deadline fast approaching, researchers across the state are busy exploring options.

Solar energy is attractive but for widespread adoption, it requires transformation into a storable form. This week in ACS Central Science, researchers report that nanowires made from multiple metal oxides could put solar ahead in this race.

One way to harness solar power for broader use is through photoelectrochemical (PEC) water splitting that provides hydrogen for fuel cells. Many materials that can perform the reaction exist, but most of these candidates suffer from issues, ranging from efficiency to stability and cost.

Peidong Yang and colleagues designed a system where nanowires from one of the most commonly used materials (TiO2) acts as a “host” for “guest” nanoparticles from another oxide called BiVO4. BiVO4 is a newly introduced material that is among the best ones for absorbing light and performing the water splitting reaction, but does not carry charge well while TiO2 is stable, cheap and an efficient charge carrier but does not absorb light well.

Together with a unique studded nanowire architecture, the new system works better than either material alone.

The authors state their approach can be used to improve the efficiencies of other photoconversion materials.

Synopsis

We report the use of Ta:TiO2|BiVO4 as a photoanode for use in solar water splitting cells. This host−guest system makes use of the favorable band alignment between the two semiconductors. The nanowire architecture allows for simultaneously high light absorption and carrier collection for efficient solar water oxidation.

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Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host–guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm2 at 1.23 V vs RHE.

Introduction


Harnessing energy from sunlight is a means of meeting the large global energy demand in a cost-effective and environmentally benign manner. However, to provide constant and stable power on demand, it is necessary to convert sunlight into an energy storage medium.(1) An example of such a method is the production of hydrogen by photoelectrochemical (PEC) water splitting. The direct splitting of water can be achieved using a single semiconductor; however, due to the voltage requirement of the water splitting reaction and the associated kinetic overpotentials, only wide-band-gap materials can perform overall water splitting, limiting the efficiency due to insufficient light absorption.(2) To address this issue, a dual-band-gap z-scheme system can be utilized, with a semiconductor photoanode and photocathode to perform the respective oxidation and reduction reactions.(3) This approach allows for the use of lower-band-gap materials that can absorb complementary portions of the solar spectrum and yield higher solar-to-fuel efficiencies.(4, 5) In this integrated system, the charge flux is matched in both light absorbers of the photoelectrochemical cell. Therefore, the overall performance is determined by the limiting component. In most photoelectrosynthetic cells, this limiting component is the semiconductor photoanode.(6)
Metal oxides have been heavily researched as photoanode materials since few conventional light absorber materials are stable at the highly oxidizing conditions required for water oxidation.(7) However, the most commonly studied binary oxide, TiO2, has a band gap that is too large to absorb sunlight efficiently (∼3.0 eV), consequently limiting its achievable photocurrent.(8) While promising work has recently been done on stabilizing conventional light absorbers such as Si,(9) GaAs,(10) and InP,(11) the photovoltage obtained by these materials thus far has been insufficient to match with smaller-band-gap photocathode materials such as Si and InP in a dual absorber photoelectrosynthetic cell.(12, 13) Additionally, these materials have high production and processing costs. Small-band-gap metal oxides that absorb visible light and can be inexpensively synthesized, such as WO3, Fe2O3, and BiVO4, are alternative materials that hold promise to overcome these limitations.(14-16) Among these metal oxides, BiVO4 has emerged as one of the most promising materials due to its relatively small optical band gap of ∼2.5 eV and its negative conduction band edge (∼0 V versus RHE).(17, 18) Under air mass 1.5 global (AM1.5G) solar illumination, the maximum achievable photocurrent for water oxidation using BiVO4 is ∼7 mA/cm2.(16) However, the water oxidation photocurrent obtained in practice for BiVO4 is substantially lower than this value, mainly due to poor carrier transport properties, with electron diffusion lengths shorter than the film thickness necessary to absorb a substantial fraction of light.(17)
One approach for addressing this problem is to use two separate materials for the tasks of light absorption and carrier transport. To maximize performance, a conductive and high surface area support material (“host”) is used, which is coated with a highly dispersed visible light absorber (“guest”). This architecture allows for efficient use of absorbed photons due to the proximity of the semiconductor liquid junction (SCLJ). This strategy has been employed in dye sensitized (DSSC) and quantum dot sensitized solar cells (QDSSC).(19, 20) Using a host–guest scheme can improve the performance of photoabsorbing materials with poor carrier transport but relies upon appropriate band alignment between the host and guest. Namely, the electron affinity of the host should be larger, to favor electron transfer from guest to host without causing a significant loss in open-circuit voltage.(21) Nanowire arrays provide several advantages for use as the host material as they allow high surface area loading of the guest material, enhanced light scattering for improved absorption, and one-dimensional electron transport to the back electrode.(22) Therefore, nanowire arrays have been used as host materials in DSSCs, QDSSCs, and hybrid perovskite solar cells.(23-25) In photoelectrosynthetic cells, host–guest architectures have been utilized for oxide photoanodes such as Fe2O3|TiSi2,(26) Fe2O3|WO3,(27) Fe2O3|SnO2,(28) and Fe2TiO5|TiO2.(29) For BiVO4, it has been studied primarily with WO3|BiVO4,(30-32) ZnO|BiVO4,(33) and anatase TiO2|BiVO4.(34) While attractive for its electronic transport properties, ZnO is unstable in aqueous environments, and WO3 has the disadvantage of having a relatively positive flatband potential (∼0.4 V vs RHE)(14) resulting in potential energy losses for electrons as they are transferred from BiVO4 to WO3, thereby limiting the photovoltage of the combined system. Performance in the low potential region is critical for obtaining high efficiency in photoelectrosynthetic cells when coupled to typical p-type photocathode materials such as Si or InP.(12, 13) TiO2 is stable in a wide range of pH and has a relatively negative flat band potential (∼0.2 V vs RHE)(7) which does not significantly limit the photovoltage obtainable from BiVO4, while still providing a driving force for electron transfer. While TiO2 has intrinsically low mobility, doping TiO2 with donor type defects could increase the carrier concentration and thus the conductivity. Indeed, niobium and tantalum doped TiO2 have recently been investigated as potential transparent conductive oxide (TCO) materials.(35, 36) A host material with high carrier concentration could also ensure low contact resistance with the guest material.(37)
Using a solid state diffusion approach based on atomic layer deposition (ALD), we have previously demonstrated the ability to controllably and uniformly dope TiO2.(38) In this study we demonstrate a host–guest approach using Ta-doped TiO2 (Ta:TiO2) nanowires as a host and BiVO4 as a guest material. This host–guest nanowire architecture allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent of 2.1 mA/cm2 at 1.23 V vs RHE. We show that the synergistic effect of the host–guest structure results in higher performance than either pure TiO2 or BiVO4. We also experimentally demonstrate thermodynamically favorable band alignment between TiO2 and BiVO4 using spectroscopic and electrochemical methods, and study the band edge electronic structure of the TiO2 and BiVO4 using X-ray absorption and emission spectroscopies.

Article adapted from a American Chemical Society news release. To Read the FULL release, please click on the link provided below.

Publication: TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment. Resasco, J et al. ACS Central Science (3 February, 2016): Click here to view.

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Video Interview with Professor Ted Sargent at the University of Toronto

With global climate change on the rise, finding ways to capture renewable energy sources is becoming more urgent. Today, our energy needs are largely being met by fossil fuels, such as oil and coal, but we are rapidly depleting these natural resources, and damaging our environment by burning them for fuel. One sustainable alternative is solar energy. Prof. Ted Sargent, an electrical engineer at the University of Toronto, is working on making a new paint-based solar cell that would be low-cost, lightweight, portable, and efficient, bringing sustainable electricity anywhere that it is needed.

We picture a world in which solar cells are so convenient. They are on a carpet that you can roll out onto your roof, or they are on a decal that you can stick on the side of a streetcar or stick on your car, you can stick on your airplane wing. And they can be kind of adhered to any surface. And they can be used to meet the power needs of that automobile or plane or helicopter or home or tent; and they are ubiquitous.

Unlike fossil fuels, Sargent explains, “the sun is this incredible, vast resource. We get more sun reaching the Earth’s surface everyday than we need to power the world’s energy needs. In fact, in an hour, we get enough to meet our energy needs for a year; it’s that abundant.” To achieve a better solar cell, Prof. Sargent is working at the interface of chemistry, physics, materials science, and electrical engineering to understand the relationships between light and electrons. He is developing a liquid for solar capture that can be applied as a paint, and that can be printed using roll-to-roll processes similar to those used to print newspapers. These paints would absorb sunlight and use it to generate electricity.

Prof. Sargent envisions solar cells that are so minimal that installing one might be as simple as unrolling a sheet onto a rooftop, or applying a decal to a streetcar or phone. “We picture a world in which solar cells are so convenient… They are so little in their consumption of materials that we change the paradigm of solar energy from one that takes planning, major capital investment, to one where it’s all over the place because it’s so compelling and convenient,” says Sargent.

How do you envision the future of energy and power? Let us know in the comments.


Prof. Ted Sargent
Prof. Ted Sargent holds the Canada Research Chair in Nanotechnology at the University of Toronto, where he also serves as Vice Dean for Research for the Faculty of Applied Science and Engineering. He is a Fellow of the Royal Society of Canada, a Fellow of the AAAS “for distinguished contributions to the development of solar cells and light sensors based on solution-processed semiconductors” and a Fellow of the IEEE “for contributions to colloidal quantum dot optoelectronic devices.” He is CTO of InVisage Technologies of Menlo Park, CA; and is a co-founder of Xagenic Inc.

Fourth Industrial Revo 012016 AAEAAQAAAAAAAAZqAAAAJGM1YzM0NGYxLWIxZTMtNGYyNi1iMjIyLTM1MjUwNDRjYjIyYQFulvia Montresor, Director, World Economic Forum ~ From intelligent robots and self-driving cars to gene editing and 3D printing, dramatic technological change is happening at lightning speed all around us.

The Fourth Industrial Revolution is being driven by a staggering range of new technologies that are blurring the boundaries between people, the internet and the physical world. It’s a convergence of the digital, physical and biological spheres. It’s a transformation in the way we live, work and relate to one another in the coming years, affecting entire industries and economies, and even challenging our notion of what it means to be human.

So what exactly are these technologies, and what do they mean for us?

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Computing capabilities, storage and access

Between 1985 and 1989, the Cray-2 was the world’s fastest computer. It was roughly the size of a washing machine. Today, a smart watch has twice its capabilities.

As mobile devices become increasingly sophisticated, experts say it won’t be long before we are all carrying “supercomputers” in our pockets. Meanwhile, the cost of data storage continues to fall, making it possible keep expanding our digital footprints.

Today, 43% of the world’s population are connected to the internet, mostly in developed countries. The United Nations has set the goal of connecting all the world’s inhabitants to affordable internet by 2020. This will increase access to information, education and global marketplaces, which will empower many people to improve their living conditions and escape poverty. Imagine a world where everyone is connected by mobile devices with unprecedented processing power and storage capacity!

If we can achieving the goal of universal internet access and overcome other barriers such as digital illiteracy, everybody could have access to knowledge, and all the possibilities this brings.

Big Data

Each time you run a Google search, scan your passport, make an online purchase or tweet, you are leaving a data trail behind that can be analysed and monetized.

Thanks to supercomputers and algorithms, we can make sense of massive amounts of data in real time. Computers are already making decisions based on this information, and in less than 10 years computer processors are expected to reach the processing power of the human brain. This means there’s a good chance your job could be done by computers in the coming decades. Two Oxford researchers, Carl Bendikt Frey and Michael A Osborne, estimated that 47% of American jobs are at high risk of automation.

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A survey done by the Global Agenda Council on the Future of Software & Society shows people expect artificial intelligence machines to be part of a company’s board of directors by 2026.

Digital Health

Analyzing medical data collated from different populations and demographics enables researchers to understand patterns and connections in diseases and identify which conditions improve the effectiveness of certain treatments and which don’t.

Big data will help to reduce costs and inefficiencies in healthcare systems, improve access and quality of care, and make medicine more personalized and precise.

In the future, we will all have very detailed digital medical profiles … including information that we’d rather keep private. Digitization is empowering people to look after their own health. Think of apps that track how much you eat, sleep and exercise, and being able to ask a doctor a question by simply tapping it into your smartphone.

In addition, advances in technologies such as CRISPR/Cas9, which unlike other gene-editing tools, is cheap, quick and easy to use, could also have a transformative effect on health, with the potential to treat genetic defects and eradicate diseases.

The digitization of matter

3D printers will create not only cars, houses and other objects, but also human tissue, bones and custom prosthetics. Patients would not have to die waiting for organ donations if hospitals could bioprint them. In fact, we may have already reached this stage: in 2014, doctors in China gave a boy a 3D-printed spine implant, according to the journal Popular Science.

The 3D printing market for healthcare is predicted to reach some $4.04 billion by 2018. According to a survey by the Global Agenda Council on the Future of Software and Society, most people expect that the first 3D printed liver will happen by 2025. The survey also reveals that most people expect the first 3D printed car will be in production by 2022.

Three-dimensional printing, which brings together computational design, manufacturing, materials engineering and synthetic biology, reduces the gap between makers and users and removes the limitations of mass production. Consumers can already design personalized products online, and will soon be able to simply press “print” instead of waiting for a delivery.

The Internet of Things (IOT)

Within the next decade, it is expected that more than a trillion sensors will be connected to the internet. If almost everything is connected, it will transform how we do business and help us manage resources more efficiently and sustainably. Connected sensors will be able to share information from their environment and organize themselves to make our lives easier and safer. For example, self-driving vehicles could “communicate” with one another, preventing accidents.

By 2020 around 22% of the world’s cars will be connected to the internet (290 million vehicles), and by 2024, more than half of home internet traffic will be used by appliances and devices.

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Home automation is also happening fast. We can control our lights, heating, air conditioning and security systems remotely, but how much longer will it be before sensors are able to detect crumbs under the table and tell our automated vacuum cleaners to tidy up? The internet of things will create huge amounts of data, raising concerns over who will own it and how it will be stored. And what about the possibility that your home or car could be hacked?

Blockchain

Only a tiny fraction of the world’s GDP (around 0.025%) is currently held on blockchain, the shared database technology where transactions in digital currencies such as the Bitcoin are made. But this could be about to change, as banks, insurers and companies race to work out how they can use the technology to cut costs.

A blockchain is essentially a network of computers that must all approve a transaction before it can be verified and recorded. Using cryptography to keep transactions secure, the technology provides a decentralized digital ledger that anyone on the network can see.

Before blockchain, we relied on trusted institution such as a bank to act as a middleman. Now the blockchain can act as that trusted authority on every type of transaction involving value including money, goods and property. The uses of blockchain technology are endless. Some expect that in less than 10 years it will be used to collect taxes. It will make it easier for immigrants to send money back to countries where access to financial institutions is limited.

And financial fraud will be significantly reduced, as every transaction will be recorded and distributed on a public ledger, which will be accessible by anyone who has an internet connection.

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Source: Financial Times

Wearable internet

Technology is getting increasingly personal. Computers are moving from our desks, to our laps, to our pockets and soon they will be integrated into our clothing. By 2025, 10% of people are expected to be wearing clothes connected to the internet and the first implantable mobile phone is expected to be sold.

Implantable and wearable devices such as sports shirts that provide real-time workout data by measuring sweat output, heart rate and breathing intensity are changing our understanding of what it means to be online and blurring the lines between the physical and digital worlds.

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The potential benefits are great, but so are the challenges. These devices can provide immediate information about our health and about what we see, or help locate missing children. Being able to control devices with our brains would enable disabled people to engage fully with the world. There would be exciting possibilities for learning and new experiences.

But how would it affect our personal privacy, data security and our personal relationships? In the future, will it ever be possible to be offline anymore?

 

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 Genesis Nanotechnology, Inc. – GNT™
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