First-principles screening of Pt doped Ti₂CNL (N = O, S and Se, L = F, Cl, Br and I) as high-performance catalysts for ORR/OER

Developing high-activity and low-cost oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts is strategic to metal-air batteries. Herein, based on the idea that functionalized atoms can adjust the electronic properties of MXenes-based catalysts, we have screened some catalysts with high catalytic activity for ORR/OER using first-principles calculations. Specifically, we firstly explored the stability of Pt doped Ti₂CNL ((N = F, Cl, Br and I, L = O, S and Se)) and Ti₂CN(L)₂ though calculating the vacancy formation energy and binding energy. Moreover, compared the overpotential of Pt doped Ti₂CN(L)₂ and Ti₂CNL for ORR and OER, the Janus-MXenes configurations can tune the d-band center, work-function, density of state (DOS) and charge distribution of the catalysts, and then improve the catalytic performance of catalysts. Pt-V_S-Ti₂CSBr, Pt-V_I-Ti₂COI and Pt-V_S-Ti₂CSBr as ORR, OER and ORR/OER bifunctional catalysts were revealed due to their ultra-low overpotential of 0.35, 0.34 and 0.79 V, respectively. Additionally, compared to H ions, the catalyst preferentially adsorbs O₂, thus ensuring the ORR advantage to proceed rather than hydrogen evolution reaction (HER). Even so, Pt-VO-Ti₂COI, Pt-VS-Ti₂CSI and Pt-VSe-Ti₂CSeI have high activity for HER. Our work not only screened out catalysts with encouraging catalytic performance but also guided the design of high-performance catalysts.