Role of Electrochemical Activation in Evaluating Oxygen Evolution Activity of Ni-Incorporated Bimetallic Tungstate in Alkaline Media

Hydrogen is considered the future fuel and promising alternative towards carbon neutrality. In this context, water electrolysis using renewable electricity is an environmentally benign approach for clean hydrogen production. In water electrolysis, among the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), OER is the rate-limiting due to slow kinetics, high overpotential, and complex pathways. To catalyze the OER, choice of non-precious electrocatalysts is preferred over the precious platinum group metal (PGM)-based catalysts owing to their relatively higher abundance and cost-effectiveness. The feasibility of using non-precious electrocatalysts in alkaline water electrolysis is also favorable for the low-capital cost compared to the acidic one. In lab scale research, the preliminary evaluation of OER electrocatalysts is usually performed using thin-film rotating disk electrodes (TF-RDEs) in a three-electrode system. In this process, the very first step involves multiple cyclic voltammetry (CV) cycles for better wettability of the catalyst layer to the electrolyte, which is considered as electrochemical activation (EA). Incomplete activation of the catalyst layer would lead to inconsistent OER performance of the electrocatalysts. This is much more pronounced in non-precious electrocatalysts compared to the precious ones in alkaline media. Despite that the importance of EA is overlooked most of the time and rarely studied. In this work, the critical role of EA is systematically investigated for Ni-containing bimetallic tungstate in alkaline OER and also compared with that of monometallic counterparts. This study demonstrates more than 1.2-fold performance improvement in OER for bimetallic tungstate. The corresponding insights on the interfacial structure and oxidative surface reconstruction are also noted by using in-situ electrochemical analysis and ex-situ characterizations. The present study is believed to be beneficial for the precise analysis and development of non-precious alkaline OER electrocatalysts.