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 BiVO 4 photoanodes. The optimized BiVO 4 /NiFe(OH) x photoanode exhibits an above 300% increase in the photocurrent density over BiVO 4, 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 BiVO 4 photoanodes to 0.78% (at 0.87 V vs RHE). It reduces the water-splitting onset potential by 280 mV. Consequently, the BiVO 4 /NiFe(OH) x photoanode exhibits a 2-fold increase in the photocatalytic hydrogen production rate compared to pristine BiVO 4 . This work underscores the effectiveness of pairing facile NiFe(OH) x OECs with BiVO 4 photoanodes, leading to exceptional photoelectrochemical water oxidation.