Zinc-modulated ruthenium/ruthenium dioxide (Ru/RuO2) heterostructure enabled oxide path mechanism for efficient and durable acidic oxygen evolution.

Abstract

To regulate reaction pathways of Ru-based catalysts for overcoming activity-stability trade-off in acidic oxygen evolution reaction (OER), zinc-modulated ruthenium/ruthenium dioxide (Ru/RuO2) heterostructure catalyst (Ru/RuZnO-300) was prepared by calcining Ru-modified Zn-BTC (H3BTC = trimesic acid) metal-organic framework (MOF) for efficient and durable acidic OER. The Ru/RuO2 heterointerface containing metallic Ru and RuO2 region regulated charge distribution of RuO, while Zn introduction may have modulated the local metal‑oxygen coordination environment and favored the proposed oxide path mechanism (OPM). Operando Fourier transform infrared spectroscopy (FTIR) confirmed formation of oxygen‑oxygen coupling species during OER. Density functional theory (DFT) calculations indicated Ru/RuZnO-300 exhibited a more balanced metal‑oxygen electronic structure with moderate Ru d-O p energy level difference and relatively high Ru d-band center, which optimized adsorption behavior of oxygen-containing intermediates. The OPM pathway dominated over Ru/RuZnO-300 catalyst with a reduced thermodynamic limiting free-energy change of 1.76 eV, superior to conventional adsorbate evolution mechanism (AEM, 1.94 eV) or lattice oxygen mechanism (LOM, 2.08 eV) routes. The optimized Ru/RuZnO-300 catalyst exhibited an ultra-low overpotential of 176 mV at 10 mA·cm-2 in 0.5 M sulfuric acid (H2SO4) without ohmic potential drop (iR) compensation and remained stable for 2000 h with a small degradation rate of 14 μV·h-1. This work provided an effective strategy for simultaneously enhancing activity and stability of Ru-based catalysts through synergetic doping and heterostructure.

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