[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.]
Rice team demonstrates plasmonic hot-electron solar water-splitting technology; simpler, cheaper and efficient
September 05, 2015
Researchers at Rice have demonstrated an efficient new way to use solar energy for water splitting. The technology, described in a paper in the ACS journal Nano Letters, relies on a novel plasmonic photoelectrode architecture of light-activated gold nanoparticles that harvest sunlight to drive photocatalytic reactions by efficient, non-radiative plasmon decay into “hot carriers”—highly excited electrons.
In contrast to past work, the new architecture does not utilize a Schottky junction—the commonly used building block to collect hot carriers. Instead, the team observed large photocurrents from a Schottky-free junction due to direct hot electron injection from plasmonic gold nanoparticles into the reactant species upon plasmon decay.
JCAP team reports first complete “artificial leaf”; >10% solar-to-hydrogen conversion efficiency
August 28, 2015
Researchers at the Joint Center for Artificial Photosynthesis (JCAP) report the development of the first complete, efficient, safe, integrated solar-driven system—an “artificial leaf”—for splitting water to produce hydrogen. JCAP is a US Department of Energy (DOE) Energy Innovation Hub established at Caltech and its partnering institutions in 2010.
The new system has three main components: two electrodes—one photoanode and one photocathode—and a membrane. The photoanode uses sunlight to oxidize water molecules, generating protons and electrons as well as oxygen gas. The photocathode recombines the protons and electrons to form hydrogen gas. A key part of the JCAP design is the plastic membrane, which keeps the oxygen and hydrogen gases separate. If the two gases are allowed to mix and are accidentally ignited, an explosion can occur; the membrane lets the hydrogen fuel be separately collected under pressure and safely pushed into a pipeline.
Berkeley Lab researchers advance hybrid bioinorganic approach to solar-to~chemicals conversion; 50% electrical-to-chemical, 10% solar-to-chemical efficiencies
August 25, 2015
A team of researchers at the US Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have hit a new milestone in their development of a hybrid bioinorganic system for solar-to-chemical energy conversion. (Earlier post.) The system first generates renewable hydrogen from water splitting using sustainable electrical and/or solar input and biocompatible inorganic catalysts. The hydrogen is then used by living cells as a source of reducing equivalents for conversion of CO2 to the value-added chemical product methane.
The system can achieve an electrical-to-chemical efficiency of better than 50% and a solar-to-chemical energy conversion efficiency of 10% if the system is coupled with state-of-art solar panel and electrolyzer, said Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division and one of the leaders of this study. A paper on their work is published in Proceedings of the National Academy of Sciences (PNAS).
Volkswagen AG coordinating new €6M EU research project on drop-in biocatalytic solar fuels
June 26, 2015
Volkswagen AG is coordinating a new €6-million (US$6.7-million) research project, selected for funding under the Horizon 2020 Programme, to advance the biocatalytic production of drop-in liquid hydrocarbon transportation fuels, requiring only sunlight, CO2 and water.
The basic approach of the new 4-year Photofuel project is to develop and to advance microbes (the biocatalysts) that will directly excrete hydrocarbon and long-chain alcohol fuel compounds to the growth medium, from which the fuels are separated, without the need to harvest biomass. This basic concept is in line with the fundamental approach (CO2 + water + renewable energy → drop-in fuels) being taken by Audi (a member of the Volkswagen Group) in its e-fuels initiatives. (Earlier post.)
Joule issued patent on production of medium chain-length alkanes from sunlight and CO2; diesel, jet fuel and gasoline
June 16, 2015
Joule, the developer of engineered photosynthetic bacteria as catalysts for the direct production of targeted fuel molecules in a continuous, single-step conversion process, announced the issuance of an additional patent, extending its ability to target the highest-value molecules of the petroleum distillation process and generate them on demand from sunlight and CO2.
US Patent Nº 9,034,629, issued on 19 May, covers both the cyanobacterium and the process for directly converting CO2 into medium chain-length alkanes (C7-11), which are in the diesel, jet fuel and gasoline ranges.
“Energiewende” in a tank; Audi e-fuels targeting carbon-neutral driving with synthetic fuels from renewables, H2O and CO2; Swiss policy test case
June 12, 2015
Like other major automakers, Audi (and its parent Volkswagen Group) is working on meeting its medium-term regulatory requirements (e.g., in the 2020 timeframe) by reducing the average fuel consumption of its new vehicles using a combination of three primary measures: optimizing its combustion engines for greater efficiency; developing alternative drive concepts, such as hybrid, plug-in hybrid and gas-powered vehicles; and reducing total vehicle weight through lightweight construction with an intelligent multimaterial mix.
Unlike the others, however, Audi over the past few years has embarked on a comprehensive approach to developing a range of new CO₂-neutral fuels as part of its overall strategy for sustainable, carbon-neutral mobility: Audi e-fuels. Audi’s basic goal is to combine renewable energy (e.g. solar and wind), water and CO2 to produce liquid or gaseous fuels with a very low carbon intensity. Audi e-fuels are intended to use no fossil or biomass sources; do not compete with food production; and are 100% compatible with existing infrastructure.
Delivery of renewable isooctane to Audi tips interesting potential non-biomass pathway for biogasoline; “e-benzin” as solar fuel
May 26, 2015
Last week, Audi and its partner Global Bioenergies announced that the first batch of renewable isooctane—which Audi calls “e-benzin”—using Global Bioenergies’ fermentative isobutene pathway (sugar→isobutene→isooctane) had been produced and presented to Audi by Global Bioenergies. (Earlier post.)
Global Bioenergies, founded in 2008, has developed a synthetic isobutene pathway that, when implanted in a micro-organism, enables the organism to convert sugars (e.g., from starch and biomass) via fermentation into gaseous isobutene via a several-stage enzymatic process. However, following the delivery of the first renewable isooctane, Reiner Mangold, Audi’s head of sustainable product development, said that Audi was “now looking forward to working together with Global Bioenergies on a technology allowing the production of renewable isooctane not derived from biomass sources”—i.e., using just water, H2, CO2 and sunlight.
Audi partner Joule announces its “CO2-recycled” ethanol meets US and Euro specs; $40M financing
May 11, 2015
Joule, the developer of a direct, single-step, continuous process for the production of solar hydrocarbon fuels using engineered cyanobacteria (earlier post), announced the successful results from third-party testing of its ethanol fuel (Sunflow-E), setting the stage to obtain certification for commercial use.
Initiated by Audi, Joule’s strategic partner in the automotive space (earlier post), the test results confirm that Joule’s ethanol meets: American Society for Testing and Materials (ASTM) D4806 – Denatured fuel ethanol for blending with gasolines for use as automotive spark-ignition engine fuel; and German Institute for Standardization (DIN) EN 15376 – Ethanol as a blending component for petrol.
DOE to re-fund Joint Center for Artificial Photosynthesis with $75M for solar fuels R&D
April 29, 2015
The US Department of Energy announced $75 million in funding to renew the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub originally established in 2010 with the goal of harnessing solar energy for the production of fuel. (Earlier post.)
Under the renewal plan, the five-year-old center would receive funding for an additional five years of research, subject to Congressional appropriations. JCAP researchers are focused on achieving the major scientific breakthroughs needed to produce liquid transportation fuels from a combination of sunlight, water, and carbon dioxide, using artificial photosynthesis.
SOLARJET demonstrates full process for thermochemical production of renewable jet fuel from H2O & CO2
April 28, 2015
The European consortium SOLARJET (Solar chemical reactor demonstration and Optimization for Long-term Availability of Renewable JET fuel) (earlier post) has experimentally demonstrated the entire process chain for the first production of renewable jet fuel via a thermochemical H2O/CO2-splitting cycle using simulated concentrated solar radiation.
The solar-to-fuel energy conversion efficiency was 1.72%, without sensible heat recovery. A total of 291 stable redox cycles were performed, yielding 700 standard liters of syngas of composition 33.7% H2, 19.2% CO, 30.5% CO2, 0.06% O2, 0.09% CH4, and 16.5% Ar, which was compressed to 150 bar and further processed via Fischer–Tropsch synthesis to a mixture of naphtha, gasoil, and kerosene. Their paper is published in the ACS journal Energy & Fuels.
Research facility in Dresden produces first batch of Audi e-diesel; sunfire’s power-to-liquid technology
April 21, 2015
A pilot plant in Dresden has started production of the synthetic fuel Audi e-diesel using water, CO2 and green power—i.e., power-to-liquid (PtL). After a commissioning phase of just four months, the research facility in Dresden started producing its first batches of high‑quality diesel fuel a few days ago. (Earlier post.)
The energy technology company sunfire is Audi’s project partner and the plant operator. The CO2 used is currently supplied by a biogas facility. In addition, initially a portion of the CO2 needed is extracted from the ambient air by means of direct air capturing, a technology of Audi’s Zurich‑based partner Climeworks.
University of Adelaide team exploring novel configuration for solar hybridized coal-to-liquids process
April 13, 2015
|Simplified flowsheet of the proposed solar hybridized coal- to-liquids (SCTL) process with the proposed solar hybridized dual fluidized bed (SDFB) gasifier. Credit: ACS, Guo et al. Click to enlarge.|
Researchers at the University of Adelaide (Australia) are proposing a novel configuration of a hybridized concentrated solar thermal (CST) dual fluidized bed (DFB) gasification process for Fischer–Tropsch liquids (FTL) fuels production. In their investigation of the process, reported in a paper in the ACS journal Energy & Fuels, they used lignite as the feedstock (Solar hybridized coal to liquids, SCTL), although the process could also be used with biomass.
Although fuel products produced via the Fischer-Tropsch process are high quality (free of sulfur, nitrogen and other contaminants found in petroleum-derived products), and coal is a plentiful and low-cost feedstock, the very high greenhouse gas emissions from coal-to-liquids production processes are a major barrier. As one approach to reducing the overall carbon intensity of FT fuels, there is growing interest in introducing concentrated solar power as a heat source into the gasification process.
UC Berkeley hybrid semiconductor nanowire-bacteria system for direct solar-powered production of chemicals from CO2 and water
April 10, 2015
Researchers at UC Berkeley have developed an artificial photosynthetic scheme for the direct solar-powered production of value-added chemicals from CO2 and water using a two-step process involving a biocompatible light-capturing nanowire array with a direct interface with microbial systems.
As a proof of principle, they demonstrated that, using only solar energy input, such a hybrid semiconductor nanowire–bacteria system can reduce CO2 at neutral pH to a wide array of chemical targets, such as fuels, polymers, and complex pharmaceutical precursors A paper on their work is published in the ACS journal Nano Letters.
UW-Madison team develops novel hydrogen-producing photoelectrochemical cell using solar-driven biomass conversion as anode reaction
March 11, 2015
Researchers at the University of Wisconsin-Madison have developed an innovative hydrogen-producing photoelectrochemical cell (PEC), using solar-driven biomass conversion as the anode reaction. In a paper in the journal Nature Chemistry, the duo reports obtaining a near-quantitative yield and 100% Faradaic efficiency at ambient conditions without the use of precious-metal catalysts for this reaction, which is also thermodynamically and kinetically more favorable than conventional water oxidation at the anode. They thus demonstrated the utility of solar energy for biomass conversion (rather than catalysts) as well as the feasibility of using an oxidative biomass conversion reaction as an anode reaction in a hydrogen-forming PEC.
Chemistry Professor Kyoung-Shin Choi and postdoc Hyun Gil Cha said that their results suggest that solar-driven biomass conversion can be a viable anode reaction that has the potential to increase both the efficiency and the utility of PECs constructed for solar-fuel production.
Harvard hybrid “bionic leaf” converts solar energy to liquid fuel isopropanol
February 10, 2015
Scientists from a team spanning Harvard University’s Faculty of Arts and Sciences, Harvard Medical School and the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed a scalable, integrated bioelectrochemical system that uses bacteria to convert solar energy into a liquid fuel. Their work integrates water-splitting catalysts comprising earth-abundant components with wild-type and engineered Ralstonia eutropha bacteria to generate biomass and isopropyl alcohol. An open access paper describing their work is published in Proceedings of the National Academy of Sciences (PNAS).
Pamela Silver, the Elliott T. and Onie H. Adams Professor of Biochemistry and Systems Biology at HMS and an author of the paper, calls the system a bionic leaf, a nod to the solar water-splitting artificial leaf invented by the paper’s senior author, Daniel Nocera, the Patterson Rockwood Professor of Energy at Harvard University. (Earlier post.)
HZB researchers characterize efficient manganese catalyst for artificial photosynthesis
January 22, 2015
Scientists at the Helmholtz Center for Materials and Energy (HZB) in collaboration with the School of Chemistry and ARC Centre of Excellence for Electromaterials Science at Monash University, Australia, have precisely characterized the electronic states of a manganese (Mn) water-splitting catalyst for artificial photosynthesis.
The team led by Professor Emad Aziz, head of the HZB Institute “Methods for Material Development“ and Professor Leone Spiccia from Monash University investigated the changes in the local electronic structure of the Mn 3d orbitals of a Mn catalyst derived from a dinuclear MnIII complex during the water oxidation cycle using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) analyses.
GWU team uses one-pot process to co-generate H2 and solid carbon from water and CO2; solar fuels
December 30, 2014
|One-pot electrolytic process produces H2 and solid carbon from water and CO2. Li et al. Click to enlarge.|
A team at George Washington University led by Professor Stuart Licht has simultaneously co-generated hydrogen and solid carbon fuels from water and CO2 using a mixed hydroxide/carbonate electrolyte in a “single-pot” electrolytic synthesis at temperatures below 650 ˚C. The work is a further development of their work with STEP (solar thermal electrochemical process)—an efficient solar chemical process, based on a synergy of solar thermal and endothermic electrolyses, introduced by Licht and his colleagues in 2009. (Earlier post, earlier post.) (In short, STEP uses solar thermal energy to increase the system temperature to decrease electrolysis potentials.)
Licht and his colleagues over the past few years have delineated the solar, optical, and electronic components of STEP. In this study, they focused on the electrolysis component for STEP fuel, producing hydrogen and graphitic carbon from water and carbon dioxide. A paper on the new work is published in the journal Advanced Energy Materials.
Caltech team proposes taxonomy for solar fuels generators; different approaches to converting sunlight to chemical fuels
December 22, 2014
Researchers at the California Institute of Technology are proposing a nomenclature and taxonomy for solar fuels generators—devices that harness energy from sunlight to drive the synthesis of chemical fuels. A number of different approaches to this technology are being pursued, many of which can be differentiated by the physical principles on which they are based, according to the Caltech team, led by Dr. Nathan Lewis.
In an open-access paper published in the RSC journal Energy & Environmental Science, Dr. Lewis and colleagues outlined their method of using the source of the asymmetry that separates photogenerated electronics and holes as the basis for their taxonomy. They identify three basic device types: photovoltaic cells, photoelectrochemical cells, and photoelectrosynthetic particulate/molecular photocatalysts.
New efficient catalytic system for the photocatalytic reduction of CO2 to hydrocarbons
December 04, 2014
|Photocatalytic reduction products formed on various catalysts. The Au3Cu@STO/TiO2 array (red arrow) was the most reactive photocatalyst in this family to generate hydrocarbons from diluted CO2. Kang et al. Click to enlarge.|
Researchers from Japan’s National Institute for Materials Science (NIMS) and TU-NIMS Joint Research Center, Tianjin University, China have developed a new, particularly efficient photocatalytic system for the conversion of CO2 into CO and hydrocarbons. The system, reported in a paper in the journal Angewandte Chemie, may be a step closer to CO2-neutral hydrocarbon fuels.
More than 130 kinds of photocatalysts have been investigated to catalyze CO2 reduction; of those, strontium titanate (SrTiO3, STO) and titania (TiO2) are two of the most investigated materials. The research team headed by Dr. Jinhua Ye decided to use both, and devised a heteromaterial consisting of arrays of coaxially aligned STO/TiO2 nanotubes.
Toshiba targeting practical implementation of conversion of solar energy and CO2 to feedstock and fuel in 2020s
December 03, 2014
|Mechanism of the technology. Source: Toshiba. Click to enlarge.|
Toshiba Corporation has developed a new technology that uses solar energy directly to generate carbon compounds from carbon dioxide and water, and to deliver a viable chemical feedstock or fuel with potential for use in industry. Toshiba introduced the technology at the 2014 International Conference on Artificial Photosynthesis (ICARP2014) on 26 November.
The long-term goal of the research work is to develop a technology compatible with carbon dioxide capture systems installed at facilities such as thermal power stations and factories, utilizing carbon dioxide to provide stockable and trailerable energy. Towards this, Toshiba said it will further improve the conversion efficiency by increasing catalytic activity, with the aim of securing practical implementation in the 2020s.
Researchers develop free-standing nanowire mesh for direct solar water-splitting to produce H2; new design for “artificial leaf”
|The mesh with BiVO4 nanowire photoanode for water oxidation and Rh-SrTiO3 nanowire photocathode for water reduction produces hydrogen gas without an electron mediator. Credit: ACS, Liu et al. Click to enlarge.|
Researchers from UC Berkeley, Lawrence Berkeley National Laboratory and Nanyang Technological University, Singapore have developed a new technology for direct solar water-splitting—i.e., an “artificial leaf” to produce hydrogen—based on a nanowire mesh that lends itself to large-scale, low-cost production. A paper describing their work is published in the journal ACS Nano.
In the design, semiconductor photocatalysts are synthesized as one-dimensional nanowires, which are assembled into a free-standing, paper-like mesh using a vacuum filtration process from the paper industry. When immersed in water with visible light irradiation (λ ≥ 400 nm), the mesh produces hydrogen gas. Although boosting efficiency remains a challenge, their approach—unlike other artificial leaf systems—is free-standing and doesn’t require any additional wires or other external devices that would add to the environmental footprint.