Trifunctional cobalt single-atom catalyst with axial chloride coordination to achieve efficient methylamine electrosynthesis: a constant-potential DFT study

Abstract

Electrochemical methylamine synthesis from nitrate (NO₃⁻) and carbon dioxide (CO₂) offers a promising approach for sustainable methylamine production, but progress remains limited due to the sluggish C–N coupling process and the lack of effective catalysts. For this purpose, a system with efficient trifunctionality, i.e., NO₃⁻ reduction, CO₂ reduction and crucial C–N coupling sites, is essential for efficient methylamine production on single-atom catalysts (SACs). Through a systematic investigation by performing constant-potential density functional theory calculations, axially chlorine-coordinated Co single-atom catalysts anchored on graphene (CoN₄(Cl)@G) with outstanding trifunctionality are identified from among a series of TMN₄(Cl)@G and TMN₄@G (TM = Fe, Co, Ni) systems. Furthermore, a distinct C–N coupling mechanism, namely, the direct coupling of the migration-capable CO species with the *NH₂ intermediate to form the key precursor *NH₂CO (*NH₂–CO → *NH₂CO), is evidenced to be both thermodynamically and kinetically feasible (with a low energy barrier of 0.48 eV). Consequently, this work presents a practical strategy for methylamine synthesis starting from graphene-supported single-atom sites, and also advances mechanistic insight into C–N bond formation.