Partially reduced Ru/RuO2 composites as efficient and pH-universal electrocatalysts for hydrogen evolution

Abstract

Efficient and long-term stable electrocatalysts for the hydrogen evolution reaction (HER) via water splitting are urgently desired to ease the energy crisis and develop the sustainability of human society. However, the HER performance of state-of-the-art Pt in non-acidic solutions is unsatisfactory due to the severely sluggish kinetics. Here, DFT theoretical calculations reveal that the Ru/RuO₂ composites enable high HER activity to be pursued under non-acidic conditions because of the distinctive Ru and RuO₂ interface, which possess not only a strong capability to adsorb and dissociate water but also appropriate binding energies of H and OH. Therefore, we employ a simple strategy, including heating under an oxygen-poor environment and/or in situ electrochemical reduction, to partially reduce RuO₂. The formed Ru/RuO₂ interfaces demonstrate superior HER activities (e.g. η₁₀ = 17 mV, 35 mV dec⁻¹ in 1 M KOH) than Pt/C (e.g. η₁₀ = 27 mV, 58 mV dec⁻¹ in 1 M KOH) at both small (10–100 mA cm⁻²) and large (1 A cm⁻²) current densities in alkaline solution and even real seawater. Comprehensive experiments were conducted to investigate the structure-HER performance relationships. Moreover, benefiting from the bifunctional character of RuO₂, a two-electrode system based on Ru/RuO₂ composites and RuO₂ exhibits the lowest cell voltage for water splitting in both 1 M KOH and 0.5 M H₂SO₄, respectively. A 300 h-stability test at 10 mA cm⁻² without an obvious decay demonstrates the industrial prospects of the Ru/RuO₂ composites to generate green energy.