Dispersed Cu (Ni, Co) in MN3 moiety on graphene as active site via electrolytic water towards electro-epoxidation of ethylene

Abstract

Ethylene oxide (EO) is an important petrochemical product, widely used in printing and dyeing, automotive, medicine, and other fields. Direct epoxidation of ethylene by electrocatalysis is a simple and sustainable route to produce EO, which can avoid the disadvantage of traditional industrial production, such as high temperature and CO2 emissions. An efficient electrocatalyst could generate active oxygen intermediate during the electrolytic water process, which escape from the tremendous activation barrier of breaking molecular oxygen. In addition, ethylene and active oxygen are both required to be adsorbed or produce interaction on the same active site, which is more effective to directly transfer oxygen. Motivated by this strategy, we used first-principle to screen the possibility of 27 single transition metal atoms in MN3 moiety as active site starting from the Gibbs free energy change (ΔG) of *O + C2H4 → *+ C2H4O. Dispersed Cu, Ni, Co can absorb both active oxygen and ethylene, and exhibits the excellent catalytic performance through stability, selectivity, thermodynamics and kinetics evaluation. Electronic structure analysis indicates that the catalytic activity roots from the high electron transfer from the absorbed ethylene to the empty M–O anti-bonding, which weaken the M–O bonding and promote the oxygen transfer. Notably, for CuN3@graphene, the applied potential to produce active oxygen intermediate is 1.53 V vs RHE, and the kinetic energy barrier for subsequent oxygen transfer to form EO is 1.00 eV. This study verified the feasibility of single atomic electrocatalysts for EO production and offers valuable clues to design/discover active center to explore experimentally.