SuSChEM: Engineering Local Conductivity in MIS Photoelectrodes for Solar-Powered Water Splitting

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Solar-powered production of hydrogen from water offers the potential to enable solar power, which is available on a transient basis, to be stored in the form of a chemical fuel. This capability would allow the energy to be stored temporarily, then deployed during times of high demand but relatively low availability of sunlight. In addition, conversion of solar energy into hydrogen fuel would help provide the foundation for a hydrogen-based transportation infrastructure incorporating fuel-cell vehicles. Efficient and cost-effective solar-powered production of hydrogen from water remains a scientific and technological challenge. This project will investigate concepts from the field of semiconductor electronics to enable new approaches to make efficient, low-cost photoelectrodes for splitting water molecules into hydrogen and oxygen using the energy in sunlight. Specifically, photoelectrodes will be designed with thick oxide layers that serve as a protective coating at the liquid water interface with the device. At a smaller scale in the photoelectrode, local regions that are electrically conductive will be designed to enable electrons to move easily between the semiconductor region where sunlight is absorbed and the aqueous solution in which the electrons help split water molecules into hydrogen and oxygen. For educational impacts, the project will introduce new components into an introductory-level course for freshman students in electrical engineering. These components will provide students with expertise required to design and to create physical prototypes of a wide range of engineered systems. By developing these capabilities at the outset of their university academic careers, students will be able to deploy them extensively throughout the remainder of their education.This project will seek to engineer localized electrical conduction paths across insulating oxide layers for efficient and stable Si-based metal-insulator-semiconductor (MIS) photoelectrodes for solar-driven water splitting. These investigations will build upon recent advances in the engineering of local conductivity via electrical breakdown in MIS devices that have enabled highly stable, Si-based MIS photocathodes and photoanodes. Three primary fundamental research directions will be pursued: (i) investigation of the influence of localized conduction paths between absorber and catalyst on photocurrent density, photovoltage and other aspects of MIS photoelectrode performance; (ii) engineering of a new, scalable approach, based on thin-film metallization reactions, for engineering and optimizing local conductivity across protective oxide layers for MIS photoelectrodes for water splitting; and (iii) characterization of spatial inhomogeneity in water splitting activity, and its relationship with material and device fabrication processes, using scanning electrochemical microscopy. Cross-fertilization spanning the disciplines of materials processing, electrochemistry, and solid-state device physics could enable increased impact of the technological infrastructure associated with silicon-based electronics and photovoltaics on solar fuel generation and the associated energy storage capability.