Precise electronic structure modulation on MXene-based single atom catalysts for high-performance electrocatalytic CO2 reduction reaction: A first-principle study

Electrocatalytic CO2 reduction reaction (CO2RR) to CO is a logical approach to achieve a carbon-neutral cycle. In this work, a series of Ti2CO2 and O vacancy containing Ti2CO2 MXene-based transition metal (TM) single atom catalysts (SACs), including TM-Ti2CO2 and TM-Ov-Ti2CO2, are explored for high-performance CO2RR. Sc/Ti/V/Cr-Ti2CO2 and Ni-Ov-Ti2CO2 are screened out with limiting potential (UL) more positive than -0.50 V. Ni-Ov-Ti2CO2 is a candidate catalyst for CO2RR to CO, considering its activity with UL of -0.27 eV, and the selectivity relevant to hydrogen evolution reaction and HCOOH production. Meanwhile, a novel activity descriptor of TM-Ti-O group valence state is proposed according to that TMs work in synergy with coordinated Ti and O atoms and a level of around 0.64 e- benefits to CO2RR. This work highlights oxygen vacancy containing Ti2CO2-based Ni SAC as a promising catalyst for CO2RR, and provides a feasible electronic structure design principle for guiding the design of MXene-based SACs for CO2RR.