A Bifunctional CoMoP-Based Electrode Enables 11.84% Solar-to-Hydrogen Efficiency in Direct PV-Driven Water...

Efficient direct photovoltaic (PV)-driven water electrolysis requires electrocatalysts that operate at current densities and potentials well matched to the PV maximum power output while maintaining stability under intermittent conditions. Herein, we report a simple one-step electrodeposition strategy to fabricate a bifunctional CoMoP-based electrocatalyst supported on stainless steel fiber felt (CoMoP/SSF) that fulfills these requirements. The fabricated electrode exhibits excellent activity toward both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), achieving OER overpotentials of 188 and 336 mV at 10 and 500 mA cm^{- 2}, respectively, and HER overpotentials of 56 and 230 mV at 20 and 500 mA cm^{- 2}, respectively. Compared with monometallic CoP/SSF and MoP/SSF electrodes, the superior performance of the bimetallic CoMoP/SSF electrode arises from synergistic electronic interactions between Co and Mo, which improve the intrinsic activity and increase the number of accessible active sites. An alkaline electrolyzer assembled using CoMoP/SSF as both anode and cathode achieved 10 and 500 mA cm^{- 2} at cell voltages of 1.53 and 1.90 V in 1 M KOH, maintaining stable operation at 500 mA cm^{- 2} for over 100 h. When integrated with a triple-junction InGaP/InGaAs/Ge PV system, the electrode demonstrated an excellent matching factor (93.5%). The integrated PV-electrolysis system achieved a solar-to-hydrogen efficiency of 11.84% at over 300 mA cm^{- 2}, outperforming most reported direct PV-driven alkaline water electrolysis systems.