MXenes modified by single transition metal atom for hydrogen evolution reaction catalysts

Highlights: • MXenes modified by single atom in three ways for HER are reported firstly. • Either the single atom or the O atom can serve as active sites for modified MXenes. • ΔG_H* for three modified MXenes catalysts can reach the ideal value, 0, when pH = 0. • The dual-active-site catalysts imply the high efficiency for hydrogen production. • Some catalysts behave well for HER in both acidic and alkaline/neutral conditions. Searching for noble-metal-free catalysts for hydrogen evolution reaction (HER) is crucial to the development of sustainable energy. Here, we systematically explored the HER catalytic performance of Ti₂CO₂, Ti₃C₂O₂ and Ti₃CNO₂ modified by single transition metal atom via first-principles calculations. The modified catalysts behave outstanding catalytic performance with either the single atom or the O atom on the surfaces of MXenes as active sites when pH = 0. We found that Ti₂CO₂ doped with Cu, Ag and W at O site exhibit superb HER catalytic performance when pH = 0 with Gibbs free energies of hydrogen adsorption of −2.67*10⁻⁵, −2.78*10⁻⁴, and 3.37*10⁻⁴ eV, respectively. In addition, Cu and Pd directly anchoring on Ti₂CO₂ have dual-acitve-site mechanism for HER, indicating high efficiency. The enhanced performance for HER is attributed to the redistribution of electron after the introduction of single atom. Furthermore, Ti₂CO₂ doped with W at Ti site, Ti₃C₂O₂ doped with Mo and W at Ti site, behave good catalytic performance via wide pH ranges under alkaline/neutral conditions. Their low water dissociation barriers imply excellent HER catalytic performance under both acidic and alkaline/neutral conditions. These explorations bring new prospect to the potential of Ti-based MXenes in HER catalysis.