Interfacial Coupling Effect on Electron Transport in Hierarchical TaON/Au/ZnCo-LDH Photoanode with Enhanced Photoelectrochemical Water Oxidation

Rational design and construction of interface heterostructures, which can simultaneously accelerate the photoinduced carrier separation and enhance the surface water oxidation kinetics, is of great necessity for photoelectrochemical (PEC) water oxidation. Herein, we report a new strategy for boosting the PEC water oxidation by introducing Schottky junction and semiconductor/water oxidation cocatalysts (SC/WOCs) junction into the TaON photocatalyst. Compared with pristine TaON photoanode, the hierarchical TaON/Au/ZnCo-LDH (LDH = layered double hydroxide) photoanode reveals a cathodic shift of 156 mV for the onset potential and 17.3-fold photocurrent density enhancement at 1.23 V vs RHE, as well as improved long-term stability. Diagnostic efficiencies of the TaON/Au/ZnCo-LDH photoanode demonstrate that the enhanced PEC performance is not dominated by surface electrochemical water oxidation kinetics but largely contributed by the improved charge separation and transfer, indicative of synergistic effects of Au and ZnCo-LDH. Theoretical calculations further reveal that the midgap states introduced by Au and ZnCo-LDH in TaON electronic structures bring about photoexcited electrons concentrated on TaON, while holes accumulated on ZnCo-LDH to achieve efficiently spatial charge separation, which is responsible for the boosted PEC water oxidation performance. The present work highlights the importance and elucidates the mechanism of interface heterojunction in PEC water oxidation, which can provide an efficient approach to design and fabricate a new structural photoanode.