Revealing the pH-Universal Electrocatalytic Activity of Co-Doped RuO<sub>2</sub> toward the Water Oxidation Reaction
Ragunath Madhu, Arun Karmakar, Sangeetha Kumaravel, Selvasundarasekar Sam Sankar, Krishnendu Bera, Sreenivasan Nagappan, Hariharan N. Dhandapani, Subrata Kundu
Abstract
Electrocatalytic water splitting has gained vast attention in recent decades for its role in catalyzing hydrogen production effectively as an alternative to fossil fuels. Moreover, the designing of highly efficient oxygen evolution reaction (OER) electrocatalysts across the universal pH conditions was more challengeable as in harsh anodic potentials, it questions the activity and stability of the concerned catalyst. Generally, geometrical engineering and electronic structural modulation of the catalyst can effectively boost the OER activity. Herein, a Co-doped RuO2 nanorod material is developed and used as an OER electrocatalyst at different pH conditions. Co-RuO2 exhibits a lower overpotential value of 238 mV in an alkaline environment (1 M KOH) with a Tafel slope value of 48 mV/dec. On the other hand, in acidic, neutral, and near-neutral environments, it required overpotentials of 328, 453, and 470 mV, respectively, to attain a 10 mA/cm2 current density. It is observed that doping of Co into the RuO2 could synergistically increase the active sites with the enhanced electrophilic nature of Ru4+ to accelerate OER in all of the pH ranges. This study finds the applicability of earth-abundant-based metals like Co to be used in universal pH conditions with a simple doping technique. Further, it assured the stable nature in all pH electrolytes and needs to be further explored with other metals in the future.