High‐Efficiency Photo‐Assisted Large Current‐Density Water Splitting with Mott‐Schottky Heterojunctions

Abstract The development of bifunctional photogenerated carrier‐assisted electrocatalytic (PCA‐EC) electrodes that operate with stability at large current‐density remains a significant challenge. Herein, we demonstrate a simple sputtering‐deposition process to synthesize a novel MnWO 4 /FeCoNi Mott‐Schottky heterojunction coating and deposit it on a pure Ti substrate to prepare high‐performance PCA‐EC electrodes, which exhibits enhanced light absorption range/intensity and rapidly separated photogenerated electron‐hole pairs. This design allows photogenerated electrons to directly participate in the hydrogen evolution reaction (HER), while the strong oxidation of photogenerated holes significantly reduces the defect formation energy of active metals, thereby facilitating the rapid reconstruction of highly active Ni(FeCo)OOH/MnOOH species for the oxygen evolution reaction (OER). As expected, the as‐prepared electrode demonstrates the overpotentials of 64 mV for the HER and 204 mV for the OER at 10 mA cm −2 under illumination. Benefiting from the stable interface with Fe/Co/Ni‐O−Mn/W bonding units, the dual‐electrode photoassisted electrolytic cell achieves long‐term stability at current densities of 500 and 1000 mA cm −2 . This work provides detailed insights into the enhancement mechanism of PCA‐EC and contributes to the development of photo‐assisted water splitting electrodes for large current‐density applications.