Fiber-in-tube RuxCr1−xOy as highly efficient electrocatalysts for pH-universal water oxidation via facile bubble desorption

Abstract

Electrospun RuxCr1−xOy nanomaterials were produced using an electrospinning technique followed by a thermal annealing process under oxidative atmospheric conditions. The morphology of the materials was controlled by adjusting the atmospheric O2 concentration during calcination, resulting in various shapes, including core-shell structures and nanofibers. The electrocatalytic activity of RuxCr1−xOy nanomaterials for the oxygen evolution reaction (OER) was assessed with voltammetry under various pH conditions. Specifically, RuxCr1−xOy_20 nanofibers (synthesized in a calcination environment composed of 20% oxygen and 80% helium gases), featuring a fiber-in-tube structure, exhibited the lowest potentials (V vs. RHE) at 10 mA cm−2, reaching 1.47 V under alkaline, 1.49 V under neutral, and 1.44 V under acidic conditions. Furthermore, these nanomaterials displayed the smallest Tafel slopes of 37.5 mV dec−1 in alkaline, 68.9 mV dec−1 in neutral, and 40.8 mV dec−1 in acidic environments. These results clearly indicate the superior OER activity of RuxCr1−xOy_20 in comparison to that of commercial Ir (Ir/C), pure RuOx (Ru/RuO2), and Ru-based electrocatalysts reported in the literature. Additionally, it displayed remarkable stability over 20 h continuous chronopotentiometry tests across all pH ranges and facilitated the desorption of oxygen bubbles generated during the OER process, leading to improved OER activity. The unique core-shell structure of RuxCr1−xOy_20, which dilutes expensive Ru with cheap Cr, presents excellent feasibility as a practical and cost-effective OER catalyst, especially considering the scarcity of pH-universal OER catalysts reported. © 2023 The Royal Society of Chemistry.