Ruthenium-cobalt oxide solid solution nanofiber: a robust bifunctional electrocatalyst for overall water splitting with superior ampere-grade-current-density electrocatalytic performance

Constructing high-performance bifunctional electrocatalysts for water electrolysis under an ampere-grade current density is crucial for practical application. Herein, ruthenium-cobalt oxide (RuCoO x ) solid solution nanofibers (SSNFs) are fabricated as robust bifunctional electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Typically, the optimized Ru 2 Co 1 O x SSNFs exhibit an ultra-low overpotential of 362 mV at 1000 mA cm -2 for OER, not only significantly superior to the prepared RuO x nanofibers (NFs), CoO x and commercial RuO 2 catalyst but also outperforming many reported typical OER electrocatalysts. In addition, the representative Ru 1 Co 1 O x SSNFs catalyst presents a good HER performance with an overpotential of only 149 mV at 1000 mA cm -2 and excellent stability over 120 h, surpassing the benchmark Pt/C catalyst. Furthermore, these catalysts are assembled to construct an alkaline overall water splitting cell, demonstrating a better performance than most of the recently reported water electrolyzers. Density functional theory calculations reveal that the addition of Co effectively modulates the d -orbitals of Ru and reduces the reaction energy barriers of O*→OOH*, benefitting to enhance the OER property. Additionally, the hybridization of Co and Ru is beneficial for modulating the strength of H* adsorption in an alkaline solution, which promotes the alkaline HER efficiency.