Solar-Driven Water Splitting by a Nanostructured NiFe(OH) _x Catalyst Incorporated BiVO₄ Photoanode

The integration of cost-effective and highly efficient oxygen evolution catalysts (OECs) profoundly impacts the performance of semiconductor photoharvesters in solar-driven water splitting. Drawing inspiration from the advantages of various transition metal oxides and hydroxide-based OECs, we demonstrate that the remarkable activity of nanostructured NiFe(OH)(x) catalysts can significantly enhance the oxygen evolution efficiency of BiVO4 photoanodes. The optimized BiVO4/NiFe(OH)(x) photoanode exhibits an above 300% increase in the photocurrent density over BiVO4, reaching a high value of 4.02 mA cm(-2) at 1.23 V vs reversible hydrogen electrode (RHE) under simulated solar light illumination (100 mW cm(-2), AM 1.5 G) in a near neutral electrolyte. Our investigations reveal that the NiFe(OH)(x) catalyst serves as an effective photohole-extracting layer, leading to the improved separation of photocarriers. The coupling of nanostructured NiFe(OH)(x) catalysts also enhances the applied bias photon-to-current conversion efficiency of the BiVO4 photoanodes to 0.78% (at 0.87 V vs RHE). It reduces the water-splitting onset potential by 280 mV. Consequently, the BiVO4/NiFe(OH)(x) photoanode exhibits a 2-fold increase in the photocatalytic hydrogen production rate compared to pristine BiVO4. This work underscores the effectiveness of pairing facile NiFe(OH)(x) OECs with BiVO4 photoanodes, leading to exceptional photoelectrochemical water oxidation.