Interface Engineering of Ultrathin Bimetallic Metal–Organic Layers on <i>α</i> ‐SnWO ₄ Nanoplate Photoanode for Remarkable Visible‐Light‐Driven Photocurrent in Water Splitting

In this study, a facile bottom-up interface-directed strategy was developed to graft ultrathin 2D CoFe bimetallic organic layers (MOLs) onto SnWO₄ nanoplates to enhance visible-light-driven water splitting. Several studies reveal that CoFe-MOLs play a multifunctional role in improving the photoelectrochemical (PEC) performance of the hybrid photoanode by enhancing light-harvesting capability, internal quantum efficiency, and charge-separation dynamics. Electronic reconstruction at the CoFe-MOLs/SnWO₄ interface suppresses the formation of SnO₂ surface defects that act as photocarrier recombination centers. The CoFe-MOLs also induce a substantial built-in photovoltage and type-II-like interfacial band alignment, facilitating efficient charge separation and transport. Interface engineering enables the hybrid photoanode to achieve a surface charge-separation efficiency exceeding 94% at 1.23 V versus the reversible hydrogen electrode (RHE), along with a remarkable photocurrent density of 1.21 mA.cm^-2 and an applied-bias photon-to-current efficiency of 0.22%. The presence of bimetallic Co-Fe sites acts as dual catalytic centers, serving as hole traps and active OER sites, thereby reducing the water oxidation overpotential and accelerating reaction kinetics. This work presents an innovative interface-engineering strategy for facial grafting ultrathin bimetallic organic layers onto semiconductor photoanodes to enable visible-light-driven water splitting.