Single-metal-atom-anchored RuN2 monolayers: A high-performance electrocatalyst for alkaline hydrogen oxidation reactions

Abstract

The development of alkaline exchange membrane fuel cells (AEMFCs) is severely hampered by the scarcity of efficient Pt-free catalysts for the anodic hydrogen oxidation reaction (HOR). In this work, we systematically explored the HOR performance of single 3d transition metal atom-doped RuN2 monolayers (TM-RuN2, TM = Ti-Zn) by density functional theory calculations. Formation energy, oxidation potential, and electronic structure analyses indicate that the Ti, V, Fe, Co, and Ni-doped RuN2 not only have a good conductivity, but also possess strong thermodynamic and electrochemical stability. For TM-RuN2, the ortho-N and metal (TM or ortho-Ru) atoms form a dual-active site for the adsorption of H* and OH*, respectively, where the adsorption strength is fine-tunable via the TM-modulated electronic structure. The HOR occurs preferentially through the H2 + OH*-H* + OH* mechanism on the pristine and Co, Ni, Cu, and Zn-doped RuN2, and the Tafel − H* + OH* mechanism on the Ti, V, Cr, Mn, and Fe-doped RuN2. The precisely balanced H* and OH* adsorption strength of Fe-RuN2 results in the ultra-low free energy barriers to HOR. Benefiting from the strong thermodynamic and electrochemical stability, good conductivity, and excellent HOR activity, Fe-RuN2 exhibits a huge potential as HOR electrocatalysts for AEMFCs.