Alexie M. Kolpak, Assistant Professor, Department of Mechanical Engineering

Water splitting over semiconductor photocatalysts using solar energy is a promising process for renewable hydrogen production, but an increase in conversion efficiency is required to make it economically viable. Increasing efficiency requires new materials with optimized (i) band alignment; (ii) visible light absorption; (iii) electron-hole separation; (iv) hydrogen and oxygen evolution activity; and (v) photo-corrosion resistance. We propose to use ab initio computations and classical molecular dynamics simulations to design novel core-shell catalysts to optimize these key metrics by taking advantage of interfacial effects. Our previous work showed that Si-oxide interface chemistry can induce a large electric field in an oxide thin film and a quasi-2D electron gas (Q2DEG) at the Si-oxide interface. We propose that in such a system, electrons (holes) will be driven to the Q2DEG (oxide surface), leading to a dramatic decrease in carrier recombination, and the field will also trap holes on the surface, enhancing catalytic activity and further increasing efficiency. The absorption spectrum, redox potentials, catalytic activity, transport properties, and field can be tuned by atomic-scale modifications (e.g., interfacial cation substitution), core diameter, shell thickness, and/or oxide choice. We will examine the coupling between these properties and the atomic structure, develop fundamental models of the interface chemistry, and design new high-efficiency photocatalysts. Both the physical insights and the new tools developed will be directly applicable to the design of tailored materials systems for other catalytic reactions, as well as for a wide variety of other applications in which interfaces play an important role, (e.g., photovoltaics, fuel cells, thermoelectrics).