Differentiating the role of Ni and Fe in NiFeOx co-catalyzed BiVO4 photoanode for water oxidation

Photoelectrochemical (PEC) water splitting is a promising technology for green hydrogen production. However, severe charge recombination at the photoanode has impeded its advancement. Incorporating co-catalyst on bismuth vanadate (BiVO 4 , BVO) photoanode could enhance the charge transfer efficiency and accelerate the surface reaction kinetics, which are two key challenges in the PEC system. Herein, NiFeO x co-catalyst is deposited on BVO (NiFeO x -BVO), enhancing the performance to 3.3 times (3.57 ​mA ​cm −2 at 1.23 ​V vs. RHE) in comparison to the pristine BVO. A systematic analysis has been engaged to unravel the individual roles of Ni and Fe in enhancing the PEC performance of NiFeO x -BVO. While the Ni enhances the charge transfer of BVO, the Fe is found to accelerate the water oxidation kinetics at the surface of photoanode. Working synergistically, the NiFeO x enhanced bulk (72.2 ​%) and surface (76.4 ​%) charge transfer efficiency compared to the pristine BVO (55.1 ​% and 30.5 ​%, respectively), measured at 1.23 ​V vs. RHE. This work provides important insights into rationally designing the cocatalysts for efficient PEC water splitting.