Electric field-assisted synthesis of multivalent WO3-x coupling with carbon nanotubes for promoting (photo-)electrocatalytic oxygen evolution reaction

To enhance the kinetic rate of oxygen evolution reaction (OER) in water splitting, a composite (WO 3-x /CNT) of multivalent WO 3-x coupling with carbon nanotube (CNT) is successfully synthesized by a facile electric field-assisted synthesis method. The characterization data indicate that an oxygen bridge structure of W– O –C is formed in WO 3-x /CNT due to strong interaction between WO 3-x and carbon nanotubes. Benefitting from this unique interfacial W– O –C structure, the electronic structure of tungsten sites is regulated through electron-transfer from tungsten atoms to carbon atoms. This obtained electronic structure promotes the intrinsic activity of WO 3-x /CNT and optimizes the adsorption of active OH∗ species. Moreover, the CNT support improves the overall conductivity. The optimal WO 3-x /CNT-2h sample exhibits an overpotential of only 326 mV (without iR compensation) at 10 mA cm −2 , much lower than that of commercial RuO 2 (341 mV). With the introduction of illumination, OER activity on WO 3-x /CNT-2h is tremendously enhanced and the overpotential is reduced to 276 mV at 10 mA cm −2 . This improvement is attributed to photo-generated holes, which creates additional active sites for OER. This work not only encourages the application of novel electrosynthesis methods for designing multivalent metal-based OER electrocatalysts but also highlights the synergistic effect of photoelectricity in enhancing OER performance.