The combined material, called
a photoanode, showed excellent stability while reaching a current density of 10 milliamps per square centimeter, the researchers reported.
The team was able to produce a hybrid silicon - based
photoanode structure that evolves oxygen at current densities above 15 mA / cm2.
«Without a membrane,
the photoanode and photocathode are close enough to each other to conduct electricity, and if you also have bubbles of highly reactive hydrogen and oxygen gases being produced in the same place at the same time, that is a recipe for disaster,» Lewis says.
«After watching
the photoanodes run at record performance without any noticeable degradation for 24 hours, and then 100 hours, and then 500 hours, I knew we had done what scientists had failed to do before,» says Ke Sun, a postdoc in Lewis's lab and the first author of the new study.
When applied to
photoanodes, the nickel oxide film far exceeded the performance of other similar films — including one that Lewis's group created just last year.
The artificial leaf that Lewis» team is developing in part at Caltech's Joint Center for Artificial Photosynthesis (JCAP) consists of three main components: two electrodes —
a photoanode and a photocathode — and a membrane.
In two years, the scientists have already pinpointed 12 new
photoanodes.
Photoanodes are key to this procedure.
They then selected the ones that seemed most promising as
photoanodes and used experiments to determine whether their calculations were right.
«The job of
the photoanode is to absorb sunlight and then use that energy to oxidize water — essentially splitting apart the H2O molecule and rearranging the atoms to form a fuel.
The technique used to identify
the photoanodes uses a combination of theory and practice — the scientists worked with a supercomputer and a database of around 60,000 materials, and used quantum mechanics to predict the properties of each material.
However, this requires a «
photoanode» — a sort of catalyst that can set the ball rolling — and researchers have had a tough time identifying them in the past.
The final product, Gregoire said, would look something like a solar panel and involve three components:
the photoanode, a photocathode, which forms the fuel, and a membrane that separates the two.
In fact,
photoanodes are so rare that in the last 40 years, scientists have only been able to find 16 of them.
Development of Solar Fuels
Photoanodes through Combinatorial Integration of Ni - La - Co-Ce and Ni - Fe - Co-Ce Oxide Catalysts on BiVO4.
Mechanistic Insights into Chemical and Photochemical Transformations of Bismuth Vanadate
Photoanodes F. M. Toma, J. K. Cooper, V. Kunzelmann, M. T. McDowell, J. Yu, D. Larson, N. J. Borys, J. W. Beeman, F. A. Houle, K. A. Oersson, and I. D. Sharp
Joel A. Haber, «Development of Solar Fuels
Photoanodes through Combinatorial Integration of Ni - La - Co-Ce Oxide and Ni - Fe - Co-Ce Oxide Catalysts on BiVO4»
Development of solar fuels
photoanodes through combinatorial integration of Ni - La - Co-Ce oxide and Ni - Fe - Co-Ce oxide catalysts on BiVO4.
According to Business Standard, the new system utilizes three main components: a membrane and two electrodes — one
photoanode and one photocathode.
(Invited) Chemical and Photochemical Transformations of Bismuth Vanadate and Catalyst Integration for Stable
Photoanodes.
Discovery of Solar Fuels
Photoanode Materials by Integrating High - Throughput Theory and Experiment.
«Today, bismuth vanadate is one of the best materials available for constructing
photoanodes,» said Sharp.
The team is also excited that the collective effort provides not only the discovery of high - performance materials, but also the advancement in scientific understanding of metal oxide
photoanodes.
Solar Fuels
Photoanodes Prepared by Inkjet Printing of Copper Vanadates P. Newhouse, D. Boyd, A. Shinde, D. Guevarra, L. Zhou, E. Soedarmadji, G. Li, J. B. Neaton, and J. M. Gregoire
Our joint theory - experiment effort has successfully identified new earth - abundant copper and manganese vanadate complex oxides that meet highly demanding requirements for
photoanodes, substantially expanding the known space of such materials.
In collaboration with the Materials Project, JCAP's high - throughput experimentation team, led by John Gregoire (Caltech), and a theory team, led by Jeff Neaton and Kristin Persson (LBNL), now have a defined means for rapid identification of the most promising classes of
photoanodes.
The poor stability of most semiconductors in the highly oxidizing environment of a solar fuels
photoanode has been a key factor limiting the use of many candidates light absorbers.
Employing a strategic combination of detailed electronic structure calculations, combinatorial materials synthesis, and both traditional and high - throughout photoelectrochemistry measurements, the JCAP team identified earth - abundant copper and manganese vanadate complex oxides that meet highly demanding requirements for
photoanodes: low band gap energy, stability under highly oxidizing conditions, and valence band alignment with respect to OER.
The scientists focused on bismuth vanadate, a thin - film semiconductor that has emerged as a leading candidate for use as
a photoanode, the positively charged part of a photoelectric cell that can absorb sunlight to split water.
«Without a membrane,
the photoanode and photocathode are close enough to each other to conduct electricity, and if you also have bubbles of highly reactive hydrogen and oxygen gases being produced in the same place at the same time, that is a recipe for disaster,» Lewis says regarding his findings published in PNAS.
Dr. Ager's research interests include the fundamental electronic and transport characteristics of photovoltaic materials, development of new
photoanodes and photocathodes based on abundant elements for solar fuels production, and the development of new oxide - and sulfide - based transparent conductors.
Bottom: Solar driven water oxidation performance of 25 mA · cm − 2 at 1.23 V vs. RHE is among the highest reported for a Si - based
photoanode; inset shows stable operation for at least 100 hours.
At
the photoanode side, water molecules are split into oxygen gas (O2), electrons and hydrogen protons through oxidation in the presence of sunlight and the thin film coating the team recently developed.
Development of solar fuels
photoanodes through combinatorial integration of Ni — La — Co — Ce oxide catalysts on BiVO4.
Stable solar - driven oxidation of water by semiconducting
photoanodes protected by transparent catalytic nickel oxide films.
Within JCAP, Dr. Haber's research focus surrounds the application of high - throughput methods to integrate promising lead materials into functional assemblies, such as integration of electrocatalyst libraries with light absorbers to produce functional
photoanode and photocathode assemblies.
Amorphous TiO2 coatings stabilize Si, GaAs, and GaP
photoanodes for efficient water oxidation.
Effect of Tin Doping on alpha - Fe2O3
Photoanodes for Water Splitting.
Combining high throughput experimentation with theory enabled discovery of a unique solar fuels
photoanode with remarkable stability.