Metastabilizing the Ruthenium Clusters by Interfacial Oxygen Vacancies for Boosted Water Splitting Electrocatalysis

Metal–support interaction (MSI) is witnessed as an essential manner to stabilize active metals and tune catalytic activity for heterogonous water splitting. Kinetically driving the water electrolysis (WE) appeals for a rational MSI system with the coupled electron-donating/accepting (e-D/A) characters for hydrogen/oxygen evolution reactions (HER/OER). However, the metal stabilization effect by MSI will in turn restrict the deblocking of e-D/A properties and challenge the full electrocatalytic optimization. This study profiles a heterostructure featuring metastable Ru clusters on defective NiFe hydroxide (Ru/d-NiFe LDH) support as a low-precious (≈2 wt%) catalytic platform for efficient WE. It is indicated that the interfacial oxygen vacancies can deviate the stable Ru 4d⁵ orbit to a metastable Ru^2+δ state, and regulate the metal d-band center levels toward the facilitated HER/OER processes. Resultantly, the Ru/d-NiFe LDH heterostructure attains the ultralow overpotentials at 10 mA cm⁻² for Pt-beyond alkaline HER (18 mV) and OER (220 mV) with fast kinetics and durability. The symmetrical water electrolyzer delivers a promising voltage of 1.49 V at 10 mA cm⁻² in 1 m KOH and efficient seawater splitting performance. This work carries interesting opportunities in rationalizing sophisticated metal-support electrocatalysts through metal-site metastabilization engineering.