Suppressing the lattice oxygen mechanism via Mn-doping in RuO₂/Ru heterojunctions for robust acidic water splitting

The development of efficient and durable electrocatalysts for acidic water splitting is paramount for the advancement of sustainable energy conversion technologies. However, the inherent activity-stability trade-off in non‑iridium-based catalysts remains a formidable barrier to commercial deployment. Herein, a Mn-doped RuO₂/Ru heterojunction catalyst was synthesized by precisely anchoring Mn-doped RuO₂ nanoparticles onto metallic Ru nanospheres. The resulting interfacial electronic modulation facilitates electron transfer from Ru to RuO₂, thereby stabilizing the high-valent ruthenium intermediates. Simultaneously, Mn doping optimizes the electron density at the Ru active centers to ensure ideal adsorption configurations for reaction intermediates. Evaluated in 0.5 M H₂SO₄, the bifunctional Mn-RuO₂/Ru catalyst exhibits exceptional electrocatalytic performance, requiring ultra-low overpotentials of only 192 and 52 mV to deliver 10 mA cm^-2 for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Notably, the catalyst sustains continuous OER operation for over 100 h with negligible degradation, demonstrating remarkable structural integrity in highly corrosive media. Density functional theory (DFT) calculations unveil a dual-regulation mechanism. The synergy between the RuO₂/Ru interface and Mn dopants downshifts the Ru d-band center to balance intermediate adsorption, while simultaneously suppressing the unstable lattice oxygen mechanism (LOM) by weakening RuO bond covalency. When integrated into a symmetric acidic electrolyzer (Mn-RuO₂/Ru||Mn-RuO₂/Ru), a cell voltage of just 1.50 V is required to reach 10 mA cm^-2, significantly outperforming the commercial Pt/C||RuO₂ benchmark. This work provides a robust electronic engineering strategy for designing sustainable, high-performance noble-metal-lean catalysts for acidic water splitting.