Optical, morphological, and electrochemical multimodal characterization for integrated BiVO4 photoanodes

Abstract

Photoelectrochem. water splitting is a promising route for efficient conversion of solar energy to chem. fuel. However, the development of an efficient photoanode remains the primary materials challenge in the establishment of a scalable technol. for solar water splitting. The typical photoanode architecture consists of a semiconductor light absorber coated with a metal oxide that serves a combination of functions, including corrosion protection, electrocatalysis, light trapping, hole transport, and elimination of deleterious recombination sites. In addn., the functional behavior of photocatalytic systems strongly depends on the presence of structural defects and heterogeneity over different length scales. Indeed, charge trapping at interfaces and/or (photo) corrosion processes can affect catalytic performance and selectivity. Here, we show an approach to the discovery integrated photoanodes based on bismuth vanadate light absorber. Among different photoelectrode materials, BiVO is one of the most actively investigated oxide semiconductors due to its moderate bandgap, favorable conduction band position, and relatively long photocarrier lifetimes. By use of in situ optical spectroscopy and comparisons between the metal oxide coatings and their extrinsic optical and electrocatalytic properties, we present a suite of data-driven discoveries, including the scale-up of compn. regions which form optimal interfaces with BiVO . We use photoconductive at. force microscopy to correlate local surface morphol. with generated photocurrent maps at individual grain facets in BiVO . The photocurrent maps resolve the contributions from individual grains with nanometer spatial resoln. This careful anal. allows us to identify charge transfer and loss mechanism at the nanoscale that ultimately contribute to det. the macroscale properties of the material.