Multifunctional Coatings from Scalable Single Source Precursor Chemistry in Tandem Photoelectrochemical Water Splitting

Abstract

The straightforward and inexpensive fabrication of stabilized and activated photoelectrodes for application in tandem photoelectrochemical (PEC) water splitting is reported. Semiconductors such as Si, WO3 and BiVO4 can be coated with a composite layer formed upon hydrolytic decomposition of heterobimetallic single source precursors (SSPs) based on Ti and Ni or Ti and Co in a simple single-step process under ambient conditions. The resulting 3d-transition metal oxide composite films are multi-functional, as they protect the semiconductor electrode from corrosion with an amorphous TiO2 coating and act as bifunctional electrocatalysts for H2 and O2 evolution based on catalytic Ni or Co species. Thus, this approach enables the use of the same precursors for both photoelectrodes in tandem PEC water splitting, and SSP chemistry is thereby established as a highly versatile low-cost approach to protect and activate photoelectrodes. In an optimized system, SSP coating of a Si photocathode and a BiVO4 photoanode resulted in a benchmark noble-metal free dualphotoelectrode tandem PEC cell for overall solar water splitting with an applied bias solar-tohydrogen efficiency of 0.59% and a half-life photostability of five hours.