Mo-based MXenes as highly selective two-electron oxygen reduction catalysts for H2O2 production

Abstract

Hydrogen peroxide production through the electrochemical two-electron oxygen reduction presents a compelling alternative to the anthraquinone process due to the cheap starting materials and low operating temperature and pressure. Transition metal species featuring with multi-active sites, offer high electrochemical activity and selectivity. MXenes, distinguished by excellent electrical conductivity and the two-dimensional structure facilitating smooth ion transportation, further enhance the prospects of this production approach. In this study, three Mo-based MXenes were synthesized: Mo2TiC2Fx, Mo2Ti2C3Fx and Mo2CFx. Among these, Mo2TiC2Fx emerged as the most promising catalyst for 2e−ORR, achieving a remarkable H2O2 yield of up to 0.54 mol·gcat−1·h−1. Moreover, it also exhibits a high H2O2 selectivity ranging from 81.3 % at 0.2 V to 94.1 % at 0.6 V vs. RHE, coupled with an impressive faradaic efficiency of 76.4 % at 0.4 V using H-cell. Further analysis indicates that the superior 2e−ORR performance can be attributed to the presence of metallic Mo on the surface of Mo2TiC2Fx.