Enhanced Photoelectrochemical Water Splitting on Nickel-Doped Cobalt Phosphate by Modulating both Charge Transfer and Oxygen Evolution Efficiencies

Detrimental charge recombination at photoanode/electrolyte junctions severely impedes photoelectrochemical (PEC) performance. The deposition of cobalt phosphate (CoPi) onto photoanodes is an efficient approach to achieve high PEC efficiency. However, achieving performances at the required remains a huge challenge, owing to the passivation effect of CoPi. In this study, function-tunable strategy, whereby the passivation role is switched with the activation role, is exploited to modulate PEC performance through simultaneous activation of interface charge transfer and surface catalysis. By depositing nickel-doped CoPi onto a BiVO₄ (BV) substrate, the integrated system (BV/Ni₁Co₇Pi) exhibits a remarkable photocurrent density (4.15 mA cm⁻²), which is a 4.6-fold increase relative to BV (0.90 mA cm⁻²). Moreover, the satisfactory performance can be also achieved on α-Fe₂O₃ photoanode. These findings provide guidance for improving the efficiency of CoPi on photoanodes for PEC water oxidation.