Molecular Reaction Imaging of Single-Entity Photoelectrodes

Photoelectrochemical cells have the potential to convert solar energy to liquid fuels. Nanostructured electrode materials are attractive light-harvesting materials for this purpose because their nanoscale dimensions minimize charge carrier transport distances to the solid/liquid interface. However, nanoscale materials are heterogeneous, and the influence of impurities, defects, and particle size/shape on the rates and efficiencies of the fundamental processes in photoelectrochemical cells is not entirely understood. This Perspective highlights molecular reaction imaging methods that spatially resolve principal processes in photoelectrochemical cells: (1) reaction intermediate imaging, (2) surface recombination imaging, and (3) charge transport imaging. We discuss opportunities to couple optical microscopy techniques with electron or X-ray microscopy characterization tools to reveal atomic-level structure–property relationships of single-nanoentity photoelectrodes. The atomistic detail of the semiconductor/electrolyte interface may guide the design and synthesis of nanostructured electrodes for direct solar fuels production.