RuNx clusters anchored on hierarchically porous N-doped carbon spheres for efficient alkaline hydrogen evolution reaction

Abstract

Carbon-supported Ru clusters have been recognized as promising electrocatalysts for alkaline hydrogen evolution reaction (HER), but their catalytic activity is still limited by the weak metal–carbon interaction or the blockage of active sites. Herein, we report a facile method by which RuN_x clusters are in situ anchored on hierarchically porous N-doped carbon spheres (Ru/NCS) via pyrolysis of the polymer precursor of NCS containing Ru ions. Experimental results indicate that the interaction between Ru species and N-doped carbon leads to the formation of ultrafine RuN_x clusters with uniform distribution on NCS and also optimizes the Ru–H/Ru–OH bond strength, thereby promoting the rate-determining Volmer step in alkaline HER. Furthermore, the open porous structure of the NCS support is beneficial for the transport of gaseous products. Consequently, the as-synthesized Ru/NCS exhibits excellent HER performance with an overpotential of 4 mV, a low Tafel slope of 26 mV dec⁻¹, a high mass activity of 6.24 A mg Ru⁻¹ at an overpotential of 50 mV, and long-term stability over 1000 h at 10 mA cm⁻² with negligible voltage increase, outperforming state-of-the-art commercial Pt/C and Ru/C benchmarks.