MXenes as promising catalysts for water dissociation.

• MXenes show great potential for catalyzing industrially relevant processes. • MXenes (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo; W; X = C; N) exothermically adsorb water. • Activation energies for the first O H bond cleavage in H 2 O are below 0.44 eV. • MXenes dissociate water more effectively than surfaces containing noble metals. Two-dimensional few-layered transition-metal nitrides and carbides, called MXenes, have attracted a great interest given their large surface areas and their unique physicochemical properties. Motivated by the known reactivity of surfaces of bulk transition metal carbides on the mechanism behind the water-gas shift (WGS) reaction, density functional theory (DFT) calculations were employed to investigate the bonding of water and its dissociation on a set of eighteen M 2 X MXene (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, while X = C or N) surfaces. Here it is shown that all the studied MXenes exothermically adsorb water, with adsorption energies ranging from -1.43 to -2.94 eV, and greatly facilitate its dissociation, with energy barriers below 0.44 eV. These results reinforce the role of MXenes in promoting water dissociation, effectively suggesting their potential as catalysts for industrially relevant processes such as the WGS reaction. [ABSTRACT FROM AUTHOR]