BiVO4 Photoanodes Enhanced with Metal Phosphide Co-Catalysts: Relevant Properties to Boost Photoanode Performance

Achieving highly performant photoanodes for oxygen evolution is key to developing photoelectrochemical devices for solar water splitting. In this work, BiVO(4 )photoanodes are enhanced with a series of core-shell structured bimetallic nickel-cobalt phosphides (MPs), and key insights into the role of co-catalysts are provided. The best BiVO4/Ni1.5Co0.5P and BiVO4/Ni0.5Co1.5P photoanodes achieve a 3.5-fold increase in photocurrent compared with bare BiVO4. It is discovered that this enhanced performance arises from a synergy between work function, catalytic activity, and capacitive ability of the MPs. Distribution of relaxation times analysis reveals that the contact between the MPs, BiVO4, and the electrolyte gives rise to three routes for hole injection into the electrolyte, all of which are significantly improved by the presence of a second metal cation in the co-catalyst. Kinetic studies demonstrate that the significantly improved interfacial charge injection is due to a lower charge-transfer resistance, enhanced oxygen-evolution reaction kinetics, and larger surface hole concentrations, providing deeper insights into the carrier dynamics in these photoanode/co-catalyst systems for their rational design.

Automated summary

This work investigates the enhancement of BiVO4 photoanodes with a series of core-shell structured bimetallic nickel-cobalt phosphides (MPs) and provides insights into the role of co-catalysts. The best performing photoanodes achieve a 3.5-fold increase in photocurrent compared to bare BiVO4. The enhancement is attributed to the synergy between the work function, catalytic activity, and capacitive ability of the MPs. Kinetic studies reveal that the enhanced charge injection at the interface is due to lower charge-transfer resistance, improved oxygen-evolution reaction kinetics, and higher surface hole concentrations. This study provides deeper insights for the rational design of photoanode/co-catalyst systems.