Phase-Tailored RuNi Alloys with Dual-Site Synergistic Catalysis for Stable Alkaline Water Electrolysis

Phase tailoring engineering of two-dimensional RuNi alloys was achieved via a host–guest exchange strategy, which endowed oxygen evolution reaction (OER) activity exceeding that of RuO2 to the RuNi (40:250) alloy with an fcc-Ni host and hcp-Ru guest as well as hydrogen evolution reaction (HER) activity exceeding that of Pt/C to the RuNi (250:40) alloy with an fcc/hcp-Ru host and fcc-Ni guest. X-ray photoelectron spectroscopy and in situ shell-isolated nanoparticle-enhanced Raman spectroscopy revealed that their differentiated surface reconstruction induced the respective two-site synergistic catalytic effect. The hcp-Ru site in the RuNi (40:250) alloy catalyzed the oxidation of OH– ions to O–O* and then generated a bridge-mode configuration of Ru–O–O–Ni by coupling with the adjacent Ni site to facilitate O2 evolution, while the fcc-Ru site in the RuNi (250:40) alloy acted as a transfer station for H2O by forming a Ru–OH2 adsorption state, followed by fabricating a bridge-mode configuration of Ru–HO–H–Ni through connection with the adjacent Ni site to promote H2O dissociation and H2 evolution. The integrated RuNi (40:250) || RuNi (250:40) electrolyzer achieved overall water splitting at 1.49 V (10 mA cm–2), outperforming the Pt/C || RuO2 benchmark (1.54 V), and stable operation for 650 h. This work provides fresh insights into phase-dependent dual-site synergistic catalytic behaviors for advanced alloy catalysts.