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

A Mn-doped RuO 2 /Ru heterojunction was synthesized, featuring Mn-RuO 2 nanoparticles anchored onto metallic Ru nanospheres. • Through the interfacial charge transfer from Ru to RuO 2 effectively suppresses the formation of soluble RuO 4 2− species. • Mn doping further optimizes the electron density at the ruthenium sites, endowing them with an appropriate adsorption configuration. • The weakened Ru O bond covalency is key to inhibit the degradative LOM pathway in favor of the more stable AEM. • The Mn-RuO 2 /Ru demonstrates superior performance in 0.5 M H 2 SO 4 , requiring ultra-low overpotentials for OER and HER. 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 RuO 2 /Ru heterojunction catalyst was synthesized by precisely anchoring Mn-doped RuO 2 nanoparticles onto metallic Ru nanospheres. The resulting interfacial electronic modulation facilitates electron transfer from Ru to RuO 2 , 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 H 2 SO 4 , the bifunctional Mn-RuO 2 /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 RuO 2 /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 Ru O bond covalency. When integrated into a symmetric acidic electrolyzer (Mn-RuO 2 /Ru||Mn-RuO 2 /Ru), a cell voltage of just 1.50 V is required to reach 10 mA cm −2 , significantly outperforming the commercial Pt/C||RuO 2 benchmark. This work provides a robust electronic engineering strategy for designing sustainable, high-performance noble-metal-lean catalysts for acidic water splitting. The synergy of the heterointerface and Mn dopants optimizes Ru’s electronic structure, preventing over-oxidation and suppressing lattice-oxygen participation, thereby enabling exceptional acidic water splitting performance. Download: Download high-res image (130KB) Download: Download full-size image