Enhanced catalytic activity of ZnWO4 by nickel-doping in oxygen evolution reactions

Abstract

The development of efficient and low-cost metal materials is indispensable in clean energy technology. Metal tungstates have previously been reported as catalysts for oxygen evolution reactions (OER). However, ZnWO4 alone does not exhibit significant catalytic activity for OER, it requires 330 mV to drive the reaction at 10 mA cm−2. To address this issue, a self-supporting electrode mixed with tungstate is synthesized by a hydrothermal method. Notably, the Ni-doped ZnWO4 self-supporting material demonstrates improved OER catalytic activity. Specifically, when comparing ZnWO4 to ZnNiWO4, it exhibits a reduced Tafel slope by 190 mV·dec−1, resulting in an overpotential of only 110 mV at 10 mA cm−2, with long-term stability for at least 20 h. Furthermore, the d-band center of ZnNiWO4 is modeled using Materials Studio and simulated through projected density of states (PDOS) calculations. These calculations reveal that the presence of Ni activates the metal ion as an OER active site with strong orbital overlap with the reaction intermediate. This adjustment in the electronic structure of the Ni–Zn metal active site during the oxygen evolution reaction alters the adsorption energy. Consequently, doping of Ni enhances the metal's ability to adsorb *OOH radical, shifting the d-band center of ZnNiWO4 further away from the Fermi level, and facilitates rapid oxygen release.