NSF/DOE Solar Hydrogen Fuel: Engineering Surfaces, Interfaces, and Bulk Materials for Unassisted Solar Photoelectrochemical (PEC) Water Splitting

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Principal Investigator: Thomas F. JaramilloNumber: 1433442 Nontechnical DescriptionThere is growing urgency to develop renewable alternatives to fossil fuels for satisfying global energy and chemical demands. Hydrogen gas is a promising renewable fuel that can be made from sustainable resources. One particularly promising route to produce renewable hydrogen gas is photoelectrochemical (PEC) water splitting, in which the photons of solar energy are used to convert water into hydrogen and oxygen gas in the presence of a catalyst material. This proposed research effort is aimed at tackling fundamental research challenges in this field, facilitating the development of active, stable, and readily available materials that can absorb the sun's photons and use these photons to drive the splitting of water into hydrogen gas on the surface of the material. Towards this end, the proposed research effort will modify the surface chemistry of mixtures of metal oxide compounds and elements abundant in the earth's crust to enable the electronic properties that improve light absorption and catalyse water splitting. Continued studies will improve the stability of these materials in water. Graduate students and undergraduate students will be the primary researchers on this project, building the skills necessary for them to grow into future leaders in the renewable energy technology sector. The project activities also feature significant outreach efforts to the Latino community, including K-12 and undergraduate students in Puerto Rico, as well as Latino students and parents in the Palo Alto, California community. Technical DescriptionHydrogen gas is a promising renewable fuel which can be made from sustainable resources. This project will perform an integrated study of the surfaces, interfaces, and bulk materials for unassisted photoelectrochemical (PEC) splitting of water to hydrogen gas. Computational modeling suggests that a tandem cell consisting of a Si photocathode and a bismuth vanadate photoanode can reach solar-to-hydrogen (STH) efficiencies of 10%, corresponding to100 J/s of chemical energy per square meter of solar energy collection surface. The goal of this project is to gain a fundamental understanding of materials designed to achieve 10% STH in a tandem cell that is stable in acid and consists of only earth-abundant elements. To achieve this goal, Si photocathodes as well as high-performance III-V semiconductor photoanodes will be engineered for improved activity and stability in acid by modifying the surface with molybdenum sulfide nano-materials. Similarly, bismuth vanadate photoanodes will be engineered for improved electronic properties, durability, and catalysis in acids. Outcomes from studies will provide a fundamental understanding of the failure mechanisms in PEC materials. Tandem cells of Si and bismuth vanadate will be fabricated and tested for hydrogen and oxygen gas production in both the laboratory under controlled conditions and at outdoor testing facilities under true solar conditions using US Department of Energy National Renewable Energy Laboratory facilities. Overall, this approach has the potential to advance fundamental understanding while also creating new technologies with the potential for efficient and stable hydrogen production by PEC water-splitting. With respect to education and broadening participation, graduate students and undergraduate students will be the primary researchers on this project, building the skills necessary for them to grow into future leaders in the renewable energy technology sector. The project activities also feature significant outreach efforts to the Latino community, including K-12 and undergraduate students in Puerto Rico, as well as Latino students and parents in the Palo Alto, California community.