Constructing CoP/Ni₂P Heterostructure Confined Ru Sub-Nanoclusters for Enhanced Water Splitting in Wide pH Conditions

Developing efficient electrocatalysts for water splitting is of great significance for realizing sustainable energy conversion. In this work, Ru sub-nanoclusters anchored on cobalt-nickel bimetallic phosphides (Ru-CoP/Ni₂P) are constructed by an interfacial confinement strategy. Remarkably, Ru-CoP/Ni₂P with low noble metal loading (33.1 µg cm^-2) shows superior activity for hydrogen evolution reaction (HER) in all pH values, whose turnover frequency (TOF) is 8.7, 15.3, and 124.7 times higher than that of Pt/C in acidic, alkaline, and neutral conditions, respectively. Meanwhile, it only requires the overpotential of 171 mV@10 mA cm^-2 for oxygen evolution reaction (OER) and corresponding TOF is 20.3 times higher than that of RuO₂. More importantly, the Ru-CoP/Ni₂P||Ru-CoP/Ni₂P displays superior mass activity of 4017 mA mg_{noble metal} ^-1 at 2.0 V in flowing alkaline water electrolyzer, which is 105.1 times higher than that of Pt/C||IrO₂. In situ Raman spectroscopy demonstrates that the Ru sites in Ru-CoP/Ni₂P play a key role for water splitting and follow the adsorption evolution mechanism toward OER. Further mechanism studies disclose the confined Ru atom contributes to the desorption of H₂ during HER and the formation of O-O bond during OER, leading to fast reaction kinetics. This study emphasizes the importance of interface confinement for enhancing electrocatalytic activity.