# Lattice Carbon‐Mediated Ultralow‐Barrier C–C Coupling for Selective CO Electroreduction to Ethylene

## TL;DR

This study shows how lattice carbon in MXene can help convert CO into ethylene more efficiently by lowering the energy barrier for C–C coupling.

## Contribution

The discovery of a lattice carbon-mediated mechanism that enables selective and efficient C–C coupling during CO electroreduction.

## Key findings

- Lattice carbon at MXene edges promotes C–C coupling between *CO intermediates.
- The mechanism reduces the energy barrier for C–C bond formation.
- Electron transfer to CO weakens the C≡O bond and enhances ethylene selectivity.

## Abstract

Understanding the mechanistic pathways of catalytic CO2 reduction is essential for the rational design of high‐performance electrocatalysts. A key challenge in converting CO2 to multi‐carbon (C2+) products is the high energy barrier for C─C coupling, which limits both activity and selectivity. Here, using combined density functional theory (DFT) and molecular dynamics simulations, we demonstrate that lattice carbon sites at the edges of MXene (Ti2C(OH)2) serve as highly effective adsorption centers for *CO intermediates during CO electroreduction. Remarkably, these sites significantly reduce the C─C coupling barrier through a lattice carbon‐mediated mechanism (LCMM). Electronic structure analyses, including projected densities of states, Bader charge partitioning, differential charge density, and electron localization function calculations, reveal that the LCMM facilitates substantial electron transfer to adsorbed CO. This electron enrichment weakens the C≡O bond while simultaneously promoting C─C bond formation, overcoming conventional coupling limitations. Our findings provide fundamental insights into C─C bond formation mechanisms and establish new design principles for developing selective C2 electrocatalysts.

Combined DFT and molecular dynamics simulations reveal that while the lattice carbon at the MXene edge cannot directly bind CO2 to form ethylene, it acts as an active center to promote C─C coupling between adjacent *CO intermediates for ethylene production.