Enhancing electrocatalytic hydrogen evolution efficiency: tuning catalyst support pore size to optimize hydrogen adsorption–desorption kinetics

Abstract

Developing an electrocatalyst for the hydrogen evolution reaction (HER) with a facile synthesis method and superior catalytic performance is crucial for achieving cost-effective, environmentally sustainable, and efficient hydrogen energy production. Noble metal nanoparticles have been extensively utilized as HER electrocatalysts due to their high catalytic activity, tunable composition, and electronic structure. However, their widespread application is limited by high costs. A promising strategy to enhance the utilization efficiency of noble metals involves the fabrication of noble metal–carbon composites with optimized hydrogen evolution kinetics. In this study, a SiO₂-template method was employed to modulate the pore size of hollow mesoporous carbon spheres (HMCSs) by controlling the formation rate of SiO₂. Additionally, microwave-assisted pyrolysis of Ru carbonyl compounds enabled the rapid synthesis of ultrasmall Ru nanoclusters confined within HMCSs (Ru/HMCS-2-3) in only 15 minutes. The resulting Ru/HMCS-2-3 catalyst exhibited highly efficient Ru utilization and demonstrated HER activity superior to that of commercial Pt/C catalysts in alkaline solutions, achieving a current density of 10 mA cm⁻² at an overpotential of only 18.9 mV. Furthermore, Ru/HMCS-2-3 exhibited excellent cycling stability and durability, with no significant overpotential degradation observed after 1,000 cyclic voltammetry (CV) scans and negligible current density loss during a 48-hour chronoamperometry (i–t) test. In situ Raman spectroscopy, CV analysis in the hydrogen desorption region, and density functional theory (DFT) calculations revealed that the catalyst exhibits a strong H₂O adsorption, rapid H₂O dissociation at low overpotential, and excellent hydrogen adsorption–desorption kinetics. Additionally, the spatial confinement effect of HMCS-2 on Ru clusters contributed to its remarkable HER activity and stability. These findings highlight the potential of Ru/HMCS-2-3 as a highly efficient and durable HER electrocatalyst for sustainable hydrogen production.