A surface patching strategy to achieve highly efficient solar water oxidation beyond surface passivation effect

The hole trapping sites at the photoanode/electrolyte interface seriously detract from the positive effect of oxygen-vacancy on photoelectrochemical (PEC) water oxidation. In this work, a patching strategy is put forward to eliminate those charge trapping sites of the oxygen-deficient in disordered overlayer (DL) of WO3 photoanode by inactive pieces of oxygen-rich carbon nitride quantum dots (CNQDs). The patching leads to a 1.5-fold enhancement in PEC performance and a 100 mV cathodic shift of onset potential compared to the preoptimized DL-WO3 photoanode. The remarkably raised charge transfer efficiency from 60% to 87% at 1.23 V vs RHE is an indication of boosting hole transfer. Density function theory (DFT) calculations reveal that DL-WO3/CNQDs produces a stepped valence band alignment together with the removal of charge trapping sites, is capable of overcoming the hole transfer limitation at the photoanode/electrolyte interface. This study might open a window to pursue a simple but highly efficient strategy on modification of solid/liquid interface for solar to fuel conversion.