Electronic States Modulation of BiVO <sub>4</sub> with Transition Metal-Substituted Polyoxometalates to Activate Lattice Oxygen Mechanism for Efficient Water Oxidation
Zhaohui Li, Faheem Abbas, Fangfang Feng, Kaiqin Gao, Yanli Liu, Zenghui Wu, Ze Zhang, Xionghui Fu, Yi Zhu, Yuanming Zhang, Yongge Wei
Abstract
Oxygen evolution reaction (OER) is the bottleneck of photoelectrochemical (PEC) water splitting. Activating the lattice oxygen mechanism (LOM) can break the limitation of the slow O–O coupling and accelerate the water oxidation kinetics. However, the current methods for activating LOM are limited and it is crucial to develop new strategies to induce LOM. Herein, we have modified BiVO 4 with transition metal-substituted silicotungstate (X 3 SiW 9, X = Co, Ni, Cu) to form X 3 SiW 9 –BiVO 4 photoanodes, triggering the LOM by surface modification for the first time. X 3 SiW 9 can modulate the electronic structure of BiVO 4, resulting in an upward shift of the O 2 p energy band position relative to the metal 3 d energy band, increasing the overlap of the metal and oxygen orbital energy levels, and enhancing covalency between metal and oxygen, which facilitates the activation of the lattice oxygen, thus triggering the LOM and significantly improving the OER activity of BiVO 4 . The enhancement of the OER activity depends on the influence of X 3 SiW 9 on the electronic state. Among them, Co 3 SiW 9 has the greatest influence on the electronic state of BiVO 4 . Therefore, Co 3 SiW 9 –BiVO 4 exhibits the highest photocurrent density of 4.13 mA cm –2 at 1.23 V RHE, four times higher than that of BiVO 4 (1.02 mA cm –2 ). This work modifies the photoanode with transition metal-substituted polyoxometalates to modulate the energy levels of metal and oxygen to activate LOM for significantly enhanced OER activity, which provides new strategies and perspectives on the design and application of polyoxometalates for efficient OER in PEC water splitting.