Screening of single transition metal substitution in two-dimensional Mo2CT MXene electrocatalyst with ultrahigh activity for oxygen reduction reaction

The growing family of two-dimensional transition-metal carbides, nitrides, and carbonitrides (MXenes) have received increasing attention for electrocatalysis. In this work, the activity of the transition-metal substituted Mo2CTx (TM-Mo2CTx, TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) for oxygen reduction reaction (ORR) is systematically explored. The metallic properties of Mo2CTx and TM-Mo2CTx are proved by the result of band structures. The O2 adsorption results mean that after the substitution of TM, TM-Mo2CTx have the potential for catalyzing ORR. The density of states of the O2 adsorbed on V-, Mn-, and Cu-Mo2CTx shows the different oxophilicity caused by the difference of electronic structure of TM-Mo2CTx. According to the volcano plot, three TM-Mo2CTx catalysts are screened out to exhibit ultrahigh ORR activity, e.g., Mn-, Fe-, and Ni-Mo2CTx, with the overpotential of 0.27, 0.30, and 0.35 V, respectively. Their activities are even superior to Pt(111) and some reported ORR catalysts. By analyzing the electronic structure, the origin of the ultrahigh ORR activity of Mn-Mo2CTx is revealed. This work proves that incorporating some transition metals into the lattice of Mo2CTx is an effective strategy to improve their ORR performance, and can guide the design of this novel MXene electrocatalyst.