Engineering heteropolyblue hole transfer layer for efficient photoelectrochemical water splitting of BiVO4 photoanodes

Abstract

Constructing hole transport layer (HTL) has emerged as a forefront approach to enhance the efficiency of photoelectrochemical (PEC) water oxidation. Here, we introduce the concept of the heteropolyblue HTL as a solution to address the orientation anisotropy issue associated with traditional solid-phase HTL. Integrated with cobalt-based polyoxometalate oxygen evolution cocatalyst and BiVO4 substrate, a BiVO4/HPMo: Co photoanode was constructed, achieving a separation efficiency of 96% and a photocurrent density of 5.7 mA cm−2 at 1.23 V vs. RHE. Combined with the calculation results, we determined that the Mo6⁺/Mo5⁺ electron pair in heteropolyblue acts as a bridge for hole transport. The robust redox capabilities and electron-rich characteristics of heteropolyblue confer durability to the HTL and enable the continuous transport of holes, collectively expediting reaction kinetics. This work represents the initial exploration of the systematic integration of heteropolyblue with photoanodes, unveiling the considerable potential of heteropolyblue in PEC systems.