Modulating electronic asymmetry in Ru clusters to boost hydrogen evolution reaction

Advancing sustainable hydrogen production relies on the creation of effective electrocatalysts for the hydrogen evolution reaction (HER). Ruthenium (Ru) is a potential alternative to platinum due to its lower cost and high activity, yet its performance in alkaline HER remains limited by sluggish reaction kinetics. Herein, we propose a strategy to modulate electronic asymmetry within Ru clusters by anchoring Ru nanoclusters on N-doped graphene (Ru-NC), optimizing the charge distribution between high-valent Ruⁿ⁺ and metallic Ru⁰ sites. The Ru-NC catalyst, having a Ruⁿ⁺/Ru⁰ ratio of 57.1%, demonstrates superior HER activity with an overpotential of merely 29 mV at 10 mA cm^-2 and a Tafel slope of 46 mV dec^-1 in 1.0 M KOH, surpassing the performance of Pt/C catalyst. Experimental and structural analyses reveal that the asymmetric electronic configuration facilitates H₂O dissociation at Ruⁿ⁺ sites and efficient H adsorption/desorption at Ru⁰ sites, synergistically lowering energy barriers for HER intermediates. Furthermore, Ru-NC demonstrates remarkable stability, retaining its activity after 5000 cycles and operating continuously for 80 h at 100 mA cm^-2 with minimal degradation. This work highlights the pivotal role of electronic asymmetry in enhancing HER kinetics and provides a rational design principle for high-performance Ru-based electrocatalysts.