Fe ion-chelated tannic acid layer coordinates the electronic structure of Ni-WOx to enhance oxygen evolution performance

Abstract

The oxygen evolution reaction (OER) is regarded as the efficiency-limiting step because it suffers from a kinetically sluggish four-electron process in water splitting. The intrinsic catalytic activity could be improved by adjusting the electronic structure of the catalyst through interface modification engineering. In this work, Fe ion-chelated tannic acid was coated on Ni-WOx nanowires to form TA-Fe@Ni-WOx hierarchical structure by the interfacial coordination assembly process. The hierarchical structure has abundant active sites and good electrical conductivity, which exhibits extraordinary OER performance in alkaline electrolytes. Specifically, the TA-Fe@Ni-WOx catalyst requires low over-potentials of 240 and 260 mV at 20 mA cm−2 and 50 mA cm−2, respectively. X-ray photoelectron spectroscopy results confirm that the electronic structure of TA-Fe@Ni-WOx is more beneficial to OER than Ni-WOx due to the introduction of the TA-Fe nano-sheets overlayer on the surface of Ni-WOx nanowires. Furthermore, the ultraviolet photoelectron spectroscopy results confirm that the TA-Fe@Ni-WOx hierarchical structure has an upward-moving Fermi energy and a smaller ionization potential, providing a more electron-rich environment. It is demonstrated that this simple interfacial coordination assembly coating strategy is an effective way to reasonably adjust the surface properties of metal oxides for promising applications.