Nitrogen-doped graphite encapsulating RuCo nanoparticles toward high-activity catalysis of water oxidation and reduction

There remain certain critical issues for hydrogen production in both proton exchange membrane (PEM) and alkaline water electrolysis, the former of which faces daunting challenges in the development of high-activity and high-stability catalysts for acidic oxygen evolution reaction (OER), while the latter one strongly demands enhancing the sluggish kinetic of alkaline cathodic hydrogen evolution reaction (HER). Herein, we reported a facile one-step annealing strategy for fabricating hybrid electrocatalyst with RuCo alloy nanoparticles encapsulated by N-doped graphite loading on N-doped graphite nanosheets (RuCo@NG/N-GNs), which manifests highly desirable electrocatalytic features toward both acidic OER and alkaline HER with impressively high activity, fast kinetic and excellent stability. The optimized RuCo@NG/N-GNs requires a quite low overpotential of 209 mV at 10 mA cm⁻² for acidic OER with a quite low Tafel slope of 56 mV dec⁻¹, and demands a striking low overpotentials of 9 mV at 10 mA cm⁻² toward alkaline HER with a Tafel slope of as low as 30 mV dec⁻¹. Experiments combined with density functional theory (DFT) calculations reveal that the critical role of Co element in enhancing the HER and OER performance. For HER, the surface Co improves the oxophilicity of catalyst that indirectly aids the proton donation in alkaline; and for OER, surface Co itself acts as active sites to directly aid the reaction. The relatively low-cost electrocatalyst in this work is expected to inspire more innovative researches to step forward the large-scale commercial practice feasibility of PEM and alkaline water splitting.