Metal-Dependent Anchoring and Catalytic Behavior of Graphene-Supported Iridium and Nickel Single-Atom Anode Catalysts for Anion Exchange Membrane Water Electrolysis

Anion exchange membrane water electrolysis (AEMWE) is a promising platform for sustainable hydrogen production because it enables the use of non-noble metal catalysts in alkaline environments. However, conventional carbon-based anodes are prone to corrosion and structural degradation under oxidizing conditions, hindering the development of durable and active anode catalysts. To address this limitation, a graphene framework was employed as the anode, with iridium- and nickel-based single-atom catalysts (SACs) stabilizing the active sites and tailoring the interfacial environments. The impact of atomic anchoring sites, i.e., graphene edges versus basal planes, on catalytic performance and durability of the anode was examined. To deliberately control the anchoring preference of metal atoms, a post-calcination air-injection procedure is introduced, inducing moderate surface hydroxylation and stabilizing single-atom configurations on graphene. Advanced characterizations (high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure) reveal that iridium atoms preferentially anchor at the hydroxyl-group-rich graphene edges. In contrast, nickel atoms incorporate into the basal-plane carbon or nitrogen coordination sites. Edge-anchored iridium SACs demonstrate higher oxygen evolution activity but lower stability, whereas basal-anchored nickel SACs exhibit improved durability at the expense of catalytic activity. These findings establish a structure–property relationship between atomic coordination and electrochemical behavior, providing a design principle for graphene-based anode catalysts that can simultaneously enhance durability and reduce the cost of hydrogen production.