NiO-Embedded Rh Metallene Nanosheets as a Bifunctional Electrocatalyst for Isopropanol Oxidation and Hydrogen Evolution Reaction in Alkaline Media (Supporting Information)

Replacing the kinetically sluggish oxygen evolution reaction (OER) at the anode with a lower-potential organic oxidation reaction is a promising strategy to achieve highly efficient coupled water electrolysis for hydrogen production. However, designing electrocatalysts that simultaneously accelerate anodic organic oxidation and cathodic hydrogen evolution under alkaline conditions remains challenging. Here, we synthesize a novel bifunctional electrocatalyst, NiO@Rh-M, composed of two-dimensional Rh metallene with embedded nanoscale NiO domains to generate a high density of Rh–NiO heterointerfaces. Structural and spectroscopic analyses reveal that low-crystallinity NiO nanodomains are embedded in-plane within few-atomic-layer Rh metallene nanosheets, forming abundant Rh–NiO heterointerfaces. Owing to the cooperative roles of the Rh sites in dehydrogenation and hydrogen adsorption and the NiO domains in OH− enrichment and water dissociation, NiO@Rh-M exhibits markedly enhanced intrinsic activities for both isopropanol oxidation reaction (IOR) and alkaline hydrogen evolution reaction (HER). Notably, the IOR on NiO@Rh-M initiates at approximately 0.08 V vs. RHE, which is substantially lower than that on commercial Pt/C and far below the theoretical potential of the oxygen evolution reaction. The NiO@Rh-M catalyst achieves an overpotential of 39 mV at 10 mA cm−2 for HER, comparable to that of commercial Pt/C. When applied in an IOR–HER coupled electrolysis system, NiO@Rh-M enables stable performance at an applied cell voltage of 0.6 V, which is significantly lower than that for conventional water electrolysis, underscoring its exceptional advantage for energy-efficient electrolysis. This study establishes metallene-based heterointerface engineering as a powerful strategy for designing next-generation bifunctional electrocatalysts for energy-efficient hydrogen production and electrochemical molecular transformations.