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

[Display omitted] • The HOR activity of RuN 2 monolayers can be finely tuned by 3d TM doping. • The ortho -N and metal atoms in TM-RuN 2 form a dual-active site for HOR. • Fe-RuN 2 shows strong stability, good conductivity, and excellent HOR activity. • The high activity of Fe-RuN 2 is due to a well-balanced H* and OH* adsorption. 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 RuN 2 monolayers (TM-RuN 2 , 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 RuN 2 not only have a good conductivity, but also possess strong thermodynamic and electrochemical stability. For TM-RuN 2 , 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 H 2 + OH*-H* + OH* mechanism on the pristine and Co, Ni, Cu, and Zn-doped RuN 2 , and the Tafel − H* + OH* mechanism on the Ti, V, Cr, Mn, and Fe-doped RuN 2. The precisely balanced H* and OH* adsorption strength of Fe-RuN 2 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-RuN 2 exhibits a huge potential as HOR electrocatalysts for AEMFCs. [ABSTRACT FROM AUTHOR]