Inter-facet junction effects on particulate photoelectrodes

In anisotropically shaped photocatalyst particles different constituent facets may form inter-facet junctions at their adjoining edges. Using multimodal functional imaging, inter-facet junction effects on anisotropically shaped bismuth vanadate particles are revealed. Particulate semiconductor photocatalysts are paramount for many solar energy conversion technologies. In anisotropically shaped photocatalyst particles, the different constituent facets may form inter-facet junctions at their adjoining edges, analogous to lateral two-dimensional (2D) heterojunctions or pseudo-2D junctions made of few-layer 2D materials. Using subfacet-level multimodal functional imaging, we uncover inter-facet junction effects on anisotropically shaped bismuth vanadate (BiVO4) particles and identify the characteristics of near-edge transition zones on the particle surface, which underpin the whole-particle photoelectrochemistry. We further show that chemical doping modulates the widths of such near-edge surface transition zones, consequently altering particles' performance. Decoupled facet-size scaling laws further translate inter-facet junction effects into quantitative particle-size engineering principles, revealing surprising multiphasic size dependences of whole-particle photoelectrode performance. The imaging tools, the analytical framework and the inter-facet junction concept pave new avenues towards understanding, predicting and engineering (opto)electronic and photoelectrochemical properties of faceted semiconducting materials, with broad implications in energy science and semiconductor technology.