Photo-assisted electrodeposition of cobalt–phosphate (Co–Pi) catalyst on hematite photoanodes for solar water oxidation

Abstract

A photo-assisted electrodeposition approach was used to deposit a cobalt–phosphate water oxidation catalyst (“Co–Pi”) onto recently improved dendritic mesostructures of α-Fe₂O₃. A comparison between this approach, electrodeposition of Co–Pi, and Co²⁺ wet impregnation showed that photo-assisted electrodeposition of Co–Pi yields superior α-Fe₂O₃ photoanodes for photoelectrochemical water oxidation. Stable photocurrent densities of 1.0 mA cm⁻² at 1.0 V and 2.8 mA cm⁻² at 1.23 V vs. RHE measured under standard illumination and basic conditions were achieved. By allowing deposition only where visible light generates oxidizing equivalents, photo-assisted electrodeposition provides a more uniform distribution of Co–Pi onto α-Fe₂O₃ than obtained by electrodeposition. This approach of fabricating catalyst-modified metal-oxide photoelectrodes may be attractive for optimization in conjunction with tandem or hybrid photoelectrochemical cells.