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[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]

NREL researchers capture excess photon energy to produce solar fuels; higher efficiency water-splitting for H2

April 14, 2017

Scientists at the US Department of Energy’s National Renewable Energy Laboratory (NREL) have developed a proof-of-principle photoelectrochemical cell (PEC) capable of capturing excess photon energy normally lost to generating heat.

Using quantum dots (QD) and a process called Multiple Exciton Generation (MEG), the NREL researchers were able to push the peak external quantum efficiency for hydrogen generation to 114%. The advancement could significantly boost the production of hydrogen from sunlight by using the cell to split water at a higher efficiency and lower cost than current photoelectrochemical approaches. The research is outlined in a paper in Nature Energy.

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NREL sets new world efficiency record for solar hydrogen production: 16.2%

April 13, 2017

Scientists at the US Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) recaptured the record for highest efficiency in solar hydrogen production via a photoelectrochemical (PEC) water-splitting process.

The new solar-to-hydrogen (STH) efficiency record is 16.2%, topping a reported 14% efficiency in 2015 by an international team made up of researchers from Helmholtz-Zentrum Berlin, TU Ilmenau, Fraunhofer ISE and the California Institute of Technology. A paper in Nature Energy outlines how NREL’s new record was achieved. The authors are James Young, Myles Steiner, Ryan France, John Turner, and Todd Deutsch, all from NREL, and Henning Döscher of Philipps-Universität Marburg in Germany. Döscher has an affiliation with NREL.

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Ford favoring bulk-type solid-state battery for next-gen energy storage

April 05, 2017

Ford is exploring a variety of “beyond Li-ion” solutions, including Lithium-sulfur, Lithium-air and solid-state lithium-ion batteries. Of those, Ford is currently favoring a solid-state solution for several reasons, among them the better volumetric energy density this approach offers, said Ford engineer Venkat Anandan in a presentation at SAE WCX 17 in Detroit this week.

A Li-air battery, with its air cathode, is a low-cost system, Anandan said. It also offers a high theoretical specific energy density. Because the technology is similar to that of fuel cells, some of the design and engineering work that has already gone into fuel cells could be adapted for Li-air, he said. However, key drawbacks to the Li-air system are its relatively low practical energy density, low cycle life and the complexity of the system, Anandan said.

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GM, Ford R&D execs stress importance of improved, advanced fuels for future engine efficiency gains, GHG goals

April 03, 2017

In separate presentations at the 2017 SAE High Efficiency IC Engine Symposium in Detroit, R&D executives from GM and Ford each stressed the importance of improved, advanced fuels—among other technology developments—for their future engine efficiency gains and for long-term CO2 emissions goals.

David Brooks, Director for General Motors Global Propulsion Systems R&D located in Pontiac, gave a more medium-term perspective, emphasizing a pragmatic approach toward reducing CO2 with an eye to 2025. Meeting regulatory targets while keeping vehicles affordable will require the synergistic integration of fuels and engine technologies, he noted.

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Researchers create efficient, simple-to-manufacture photoanode for solar water-splitting

March 24, 2017

Researchers at Rice University and the University of Houston created an efficient, simple-to-manufacture core/shell photoanode with a highly active oxygen evolution electrocatalyst shell (FeMnP) and semiconductor core (rutile TiO2) for the photoelectrochemical oxygen evolution reaction (PEC-OER) for solar water splitting.

The lab of Kenton Whitmire, a Rice professor of chemistry, teamed up with researchers at the University of Houston and discovered that growing a layer of an active catalyst directly on the surface of a light-absorbing nanorod array produced an artificial photosynthesis material that could split water at the full theoretical potential of the light-absorbing semiconductor with sunlight. The results appear in two new studies. The first, on the creation of the catalytic films, appears in Chemistry: A European Journal. The second, which details the creation of photoanodes, appears in ACS Nano.

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Cambridge team demonstrates light-driven photoreforming of unprocessed biomass to H2 at room temperature

March 14, 2017

A team of scientists at the University of Cambridge has reported the light-driven photoreforming of cellulose, hemicellulose and lignin to H2 using semiconducting cadmium sulfide quantum dots in alkaline aqueous solution.

The system operates under visible light, is stable beyond six days and is even able to reform unprocessed lignocellulose, such as wood and paper, under solar irradiation at room temperature, presenting an inexpensive route to drive aqueous proton reduction to H2 through waste biomass oxidation. A paper on their work is published in the journal Nature Energy.

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IU team creates efficient nanographene-Re electro- and photo-catalyst for efficient reduction of CO2 to CO

March 09, 2017

Researchers at Indiana University Bloomington have synthesized a nanographene–Re (Rhenium) complex that functions as an efficient electrocatalyst and photocatalyst for the selective reduction of CO2 to CO for subsequent conversion to fuels.

The complex can selectively electrocatalyze CO2 reduction to CO in tetrahydrofuran at −0.48 V vs NHE—the least negative potential reported for a molecular catalyst. In addition, the complex can absorb a significant spectrum of visible light to photo-catalyze the chemical transformation without the need for a photo-sensitizer. A report on their work is published in the Journal of the American Chemical Society.

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CalTech, Berkeley Lab team uses new high-throughput method to identify promising photoanodes for solar fuels

March 07, 2017

Using high-throughput ab initio theory in conjunction with experiments in an integrated workflow, researchers at Caltech and Lawrence Berkeley National Laboratory (Berkeley Lab) have identified eight low-band-gap ternary vanadate oxide photoanodes which have potential for generating chemical fuels from sunlight, water and CO2. A report on their methodology and the new materials is published in the Proceedings of the National Academy of Sciences (PNAS).

Researchers globally are exploring a range of target solar fuels fuels, from hydrogen gas to liquid hydrocarbons; producing any of these fuels involves splitting water. Each water molecule consists of an oxygen atom and two hydrogen atoms. The hydrogen atoms are extracted, and then can be reunited to create highly flammable hydrogen gas or combined with CO2 to create hydrocarbon fuels, creating a plentiful and renewable energy source.

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Texas A&M team developing photocatalyst to turn CO2 into renewable hydrocarbon fuels

March 06, 2017

Researchers with the Department of Mechanical Engineering at Texas A&M University, led by Dr. Ying Li, associate professor of mechanical engineering, are developing a photocatalyst to convert CO2 into renewable hydrocarbon fuels. The photocatalyst material acts as a semiconductor, absorbing the sunlight which excites the electrons in the semiconductor and gives them the electric potential to reduce water and CO2 into carbon monoxide and hydrogen, which together can be converted to liquid hydrocarbon fuels, said Li.

The first step of the process involves capturing CO2 from emissions sources. The material, which is a hybrid of titanium oxide and magnesium oxide, uses the magnesium oxide to absorb the CO2 and the titanium oxide to act as the photocatalyst.

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Light over heat: UV-driven rhodium nanoparticles catalyze conversion of CO2 to methane

February 27, 2017

Duke University researchers have engineered rhodium nanoparticles that can harness the energy in ultraviolet light and use it to catalyze the conversion of carbon dioxide to methane, a key building block for many types of fuels. An open-access paper on the work is published in Nature Communications.

Industrial-scale catalysis for fuels and materials generally relies upon heated catalysts for heterogeneous catalytic reactions with large activation energies. Such catalytic processes demand high energy inputs, shorten catalyst lifetimes through sintering deterioration and require product selectivity to mitigate unfavorable side reactions. Researchers have recently discovered that plasmonic metal nanoparticles are photocatalytically active, and that product selectivity may be achieved by tuning photon and LSPR (localized surface plasmon resonances) energies.

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NSF to award $13M to projects focused on electrochemical and organic photovoltaic systems

February 24, 2017

The US National Science Foundation (NSF) will award more than $13 million to projects in the Energy for Sustainability program. The goal of the Energy for Sustainability program is to support fundamental engineering research that will enable innovative processes for the sustainable production of electricity and fuels, and for energy storage. Processes for sustainable energy production must be environmentally benign, reduce greenhouse gas production, and utilize renewable resources.

The focus of this funding opportunity (PD-17-7644) is on electrochemical energy systems and organic photovoltaics.

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NREL shows graded catalytic-protective layer boosts longevity of high-efficiency photocathodes for renewable hydrogen

January 09, 2017

Researchers at the US Department of Energy’s National Renewable Energy Laboratory (NREL) have developed a method which boosts the longevity of high-efficiency photocathodes in photoelectrochemical water-splitting devices. Their works demonstrates the potential of utilizing a hybridized, heterogeneous surface layer as a cost-effective catalytic and protective interface for solar hydrogen production.

In a paper published in the journal Nature Energy, they show that annealing a bilayer of amorphous titanium dioxide (TiOx) and molybdenum sulfide (MoSx) deposited onto GaInP2 results in a photocathode with high catalytic activity and stability for the hydrogen evolution reaction. The study showed that the annealing results in a graded MoSx/MoOx/TiO2 layer that retains much of the high catalytic activity of amorphous MoSx but with stability similar to crystalline MoS2.

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On the road to solar fuels and chemicals

December 27, 2016

In a new paper in the journal Nature Materials (in an edition focused on materials for sustainable energy), a team from Stanford University and SLAC National Accelerator Laboratory has reviewed milestones in the progress of solid-state photoelectrocatalytic technologies toward delivering solar fuels and chemistry.

Noting the “important advances” in solar fuels research, the review team also noted that the largest scientific and technical milestones are still ahead. Following their review, they listed some of the scientific challenges they see as the most important for the coming years.

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Hydrogen from sunlight, but as a dark reaction; time-delayed photocatalytic H2 production

December 09, 2016

A team at the Max Planck Institute for Solid State Research, Germany, and collaborators at ETH Zurich and the University of Cambridge, have developed a system that enables time-delayed photocatalytic hydrogen generation—essentially, an artificial photosynthesis system that can operate in the dark. A paper on their work is published in the journal Angewandte Chemie International Edition.

The system uses a carbon nitride-based material that can harvest and store sunlight as long-lived trapped electrons for redox chemistry in the dark. More specifically, the system comprises a partially anionic, cyanamide-functionalized heptazine polymer, which, in the presence of an appropriate electron donor, forms a radical species under irradiation that has a lifetime of more than 10 hours. This ultra-long-lived radical can reductively produce hydrogen in the presence of a hydrogen evolution catalyst in the dark on demand.

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Compact pilot plant for solar to liquid fuels production

November 09, 2016

Partners from Germany and Finland in the SOLETAIR project are building a compact pilot plant for the production of gasoline, diesel and kerosene from solar energy, regenerative hydrogen and carbon dioxide. The plant will be compact enough to fit into a shipping container.

The plant consists of three components. A direct air capture unit developed by the Technical Research Center of Finland (VTT) extracts carbon dioxide from air. An electrolysis unit developed by Lappeenranta University of Technology (LUT) produces the required hydrogen by means of solar power. A microstructured, chemical reactor—the key component of the plant—converts the hydrogen produced from solar power together with carbon dioxide into liquid fuels. This reactor was developed by KIT. The compact plant was developed to maturity and is now being commercialized by KIT spin-off INERATEC.

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Stanford team sets record for solar-to-hydrogen efficiency of solar water splitting: >30%

November 02, 2016

Researchers at Stanford University have demonstrated solar water splitting by photovoltaic-electrolysis with a solar-to-hydrogen (STH) efficiency of more than 30%—a new record. The prior record was 24.4%. An open-access paper on their work is published in the journal Nature Communications.

The system consists of two polymer electrolyte membrane electrolyzers in series with one InGaP/GaAs/GaInNAsSb triple-junction solar cell, which produces a large-enough voltage to drive both electrolyzers with no additional energy input. The solar concentration is adjusted such that the maximum power point of the photovoltaic is well matched to the operating capacity of the electrolyzers to optimize the system efficiency. The results, the researchers said, demonstrate the potential of photovoltaic-electrolysis systems for cost-effective solar energy storage.

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DOE seeking input on H2@scale: hydrogen as centerpiece of future energy system; 50% reduction in energy GHGs by 2050

September 11, 2016

Earlier this year, The US Department of Energy (DOE) national laboratories identified the potential of hydrogen to decarbonize deeply a multitude of sectors in a proposal termed “H2@Scale”. Preliminary analysis performed by the national laboratories on the H2@Scale concept indicated that nearly a 50% reduction in greenhouse gas emissions is possible by 2050 via such large-scale hydrogen production and use.

The concept sees hydrogen—a flexible, clean energy-carrying intermediate—having the potential to be a centerpiece of a future energy system where aggressive market penetration of renewables (wind and solar) are coupled with renewable hydrogen production to meet society’s energy demands across industrial, transportation, and power generation sectors using clean, renewable resources and processes.

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SLAC, Stanford team develops new catalyst for water-splitting for renewable fuels production; 100x more efficient than other acid-stable catalysts

September 02, 2016

Researchers at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have developed a new highly active and stable IrOx/SrIrO3 catalyst for the oxygen evolution reaction (OER).

The new catalyst outperforms known IrOx and ruthenium oxide (RuOx) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte. Because it requires less of the rare and costly metal iridium, the new catalyst could bring down the cost of artifical photosynthetic processes that use sunlight to split water molecules—a key step in a renewable, sustainable pathway to produce hydrogen or carbon-based fuels that can power a broad range of energy technologies. The team published their results in the journal Science.

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Swiss team develops effective and low-cost solar water-splitting device; 14.2% solar-to-hydrogen efficiency

August 25, 2016

Using commercially available solar cells and none of the usual rare metals, researchers at the Swiss Center for Electronics and Microtechnology (CSEM) and École Polytechnique Fédérale de Lausanne (EPFL) have designed an intrinsically stable and scalable solar water splitting device that is fully based on earth-abundant materials, with a solar-to-hydrogen conversion efficiency of 14.2%.

The prototype system is made up of three interconnected, new-generation, crystalline silicon solar cells attached to an electrolysis system that does not rely on rare metals. The device has already been run for more than 100 hours straight under test conditions. The method, which surpasses previous efforts in terms of stability, performance, lifespan and cost efficiency, is published in the Journal of The Electrochemical Society.

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Researchers generate methane from CO2 in one light-driven step using engineered bacteria

Using an engineered strain of the phototropic bacterium Rhodopseudomonas palustris as a biocatalyst, a team from the University of Washington, Utah State University and Virginia Polytechnic Institute and State University have reduced carbon dioxide to methane in one enzymatic step.

The work demonstrates the feasibility of using microbes to generate hydrocarbons (i.e., CH4 in this case) from CO2 in one enzymatic step using light energy. A paper on their work is published in Proceedings of the National Academy of Sciences (PNAS).

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UI, Argonne develop catalyst for more efficient solar-powered reduction of CO2 to CO for conversion to fuel

August 01, 2016

In a new study from the US Department of Energy’s Argonne National Laboratory and the University of Illinois at Chicago, researchers report devising a new transition metal dichalcogenide (TMDC) nanoarchitecture for catalytic electrochemical reduction of CO2 to carbon monoxide (CO) in an ionic liquid.

In their paper published in the journal Science, the researchers found that tungsten diselenide nanoflakes show a current density of 18.95 milliamperes per square centimeter, CO faradaic efficiency of 24%, and CO formation turnover frequency of 0.28 per second at a low overpotential of 54 millivolts. They also applied this catalyst in a light-harvesting artificial leaf platform that concurrently oxidized water in the absence of any external potential.

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Stanford solar tandem cell shows promise for efficient solar-driven water-splitting to produce hydrogen

June 23, 2016

Researchers at Stanford University, with colleagues in China, have developed a tandem solar cell consisting of an approximately 700-nm-thick nanoporous Mo-doped bismuth vanadate (BiVO4) (Mo:BiVO4) layer on an engineered Si nanocone substrate. The nanocone/Mo:BiVO4 assembly is in turn combined with a solar cell made of perovskite.

When placed in water, the device immediately began splitting water at a solar-to-hydrogen conversion efficiency of 6.2%—matching the theoretical maximum rate for a bismuth vanadate cell. Although the efficiency demonstrated was only 6.2%, the tandem device has room for significant improvement in the future, said Stanford Professor Yi Cui, a principal investigator at the Stanford Institute for Materials and Energy Sciences and senior author of an open access paper describing the work published in Scientific Advances.

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Harvard “bionic leaf 2.0” exceeds efficiency of photosynthesis in nature; hydrogen and liquid fuels

June 03, 2016

Researchers at Harvard have created a hybrid water splitting–biosynthetic system based on a biocompatible Earth-abundant inorganic catalyst system to split water into molecular hydrogen and oxygen (H2 and O2) at low driving voltages.

Grown in contact with these catalysts, the bacterium Ralstonia eutropha then consumes the produced H2 to synthesize biomass and fuels or chemical products from low CO2 concentration in the presence of O2. The scalable system has a CO2 reduction energy efficiency of ~50% when producing bacterial biomass and liquid fuel alcohols, scrubbing 180 grams of CO2 per kWh of electricity. Coupling this hybrid device to existing photovoltaic systems would yield a CO2 reduction energy efficiency of ~10%, exceeding that of natural photosynthetic systems, the researchers said in their paper published in the journal Science.

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PSI team demonstrates direct hydrocarbon fuel production from water and CO2 by solar-driven thermochemical cycles

May 26, 2016

Solar-driven thermochemical cycles offer a direct means of storing solar energy in the chemical bonds of energy-rich molecules. By utilizing a redox material such as ceria (CeO2) as a reactive medium, STCs can produce hydrogen and carbon monoxide—i.e., syngas—from water and CO2. The syngas can subsequently be upgraded to hydrocarbon fuels by the Fischer-Tropsch process.

Now, a team from the Paul Scherrer Institute (PSI) in Switzerland has demonstrated the direct production of hydrocarbon fuel—specifically methane—from water and CO2 by incorporating a catalytic process into STCs. A paper on their work is published in the RSC journal Energy & Environmental Science.

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New $30M ARPA-E program to produce renewable liquid fuels from renewable energy, air and water

April 26, 2016

The US Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) announced up to $30 million in funding for a new program for technologies that use renewable energy to convert air and water into cost-competitive liquid fuels. (DE-FOA-0001562)

ARPA-E’s Renewable Energy to Fuels through Utilization of Energy-dense Liquids (REFUEL) program seeks to develop technologies that use renewable energy to convert air and water into Carbon Neutral Liquid Fuels (CNLF). The program is focused in two areas: (1) the synthesis of CNLFs using intermittent renewable energy sources and water and air (N2 and CO2) as the only chemical input streams; and (2) the conversion of CNLFs delivered to the end point to another form of energy (e.g. hydrogen or electricity).

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