Work function and d-band center dual-modulation in hollow Ru-ZIF-8-derived Ru0–RuO2–ZnO heterointerfaces for boosted electrochemical hydrogen evolution†

Abstract

To enhance the kinetics of the electrochemical hydrogen evolution reaction (HER) in alkaline electrolytes, metallic Ru (Ru⁰)–RuO₂–ZnO heterointerfaces are constructed by pyrolyzing hollow Ru-ZIF-8 nanostructures with varying shapes. Systematic characterizations and theoretical simulations reveal that the exposed facets and oxygen vacancy (O_v) contents of the heterointerfaces depend on the shape and pyrolysis temperature of Ru-ZIF-8. Rhombic dodecahedral Ru-ZIF-8-derived nanocrystals by pyrolyzing at 900 °C expose Ru⁰{10}–RuO₂{21}–ZnO{001} heterointerfaces with suitable O_v content, resulting in an alleviated work function and a downshifted d-band center (ε_d). These structural optimizations accelerate H₂O adsorption–dissociation on the nanocrystal surface, weaken the excessively strong electronic interaction between the catalytic surface and the H* intermediate, balance the strengths of H* adsorption and H₂ desorption, facilitate the rate-determining stage (RDS, H₂ desorption), and ultimately lower the apparent activation energy for HER. As a result, an overpotential of 25.0 mV at 10 mA cm⁻² and a turnover frequency of H₂ generation of 0.23 s⁻¹ at 100 mV are achieved, surpassing other heterostructure analogues. An excellent linearity between the HER overpotentials and the Gibbs free energy change of H* adsorption is substantiated, highlighting the advantage of d-orbital manipulation in expediting activity.