Transition metal single-atoms anchored on Mo₂C MXenes for enhanced hydrogen oxidation reaction: a density functional theory study

Alkaline anion-exchange membrane fuel cells (AEMFCs) have garnered significant attention as promising energy conversion devices, yet their development remains hindered by the scarcity of efficient platinum-free electrocatalysts for the hydrogen oxidation reaction (HOR). Here, we systematically investigated the HOR catalytic performance of transition metal single-atoms supported by Mo₂C (TM-Mo₂C, TM = Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Ir, Pt) using first-principles density functional theory (DFT) calculations. Theoretical calculations indicate that the integration of TM atoms with Mo₂C substrates modulates the electronic structure, and establishes dual active sites comprising TM and adjacent Mo atoms. This synergistic configuration optimizes the adsorption free energies of key intermediates (H* and OH*), thereby regulating HOR activity. Volcano-shaped relationships are identified between the catalytic activity of TM-Mo₂C and the adsorption free energies of H* and OH*. Notably, Ru-Mo₂C exhibits ultralow free energy barriers for HOR due to its balanced H* and OH* adsorption strengths, demonstrating superior catalytic performance. Additionally, Ru-Mo₂C shows excellent thermodynamic and electrochemical stability, supported by its negative formation energy and high oxidation potential. These findings highlight Ru-Mo₂C as a promising high-performance HOR catalyst for AEMFCs, offering theoretical guidance for the rational design of efficient Pt-free electrocatalysts.