Enhanced Electrocatalytic C–N Coupling through Essential Electrochemical Potential Modulation of Cluster-Modified MXene

Urea stands as a vital industrial material with notable applications in energy and agriculture. However, the Haber–Bosch synthesis process, characterized by high energy consumption and emissions, poses significant challenges. Electrocatalytic C–N coupling offers a promising alternative but is constrained by the scarcity of efficient catalysts. In this work, Cr₄/Ti₂CO₂ is emerged as an optimal candidate with a remarkable low overpotential of 0.29 V and a kinetic energy barrier of 0.40 eV. A comprehensive investigation into the influence of electrochemical potential on C–N coupling revealed that the d orbitals of active sites in different chemical environments within the clusters led to distinct hybridization mechanisms with the π^* orbitals of adsorbed N₂, which is defined as Mixed Cooperative Orbital Hybridization Mechanism. Specifically, the synergistic activation of the N≡N bond by the d(x²-y²) of top atom and the d-band center of bottom atoms determined the critical step C–N coupling energy barrier under electrode potential regulation. Additionally, Cr₄/Ti₂CO₂ demonstrated optimal catalytic activity at a potential of 0.40 V versus the reversible hydrogen electrode (RHE) under acidic conditions (pH 0). These findings not only rationalize the design of an efficient electrocatalyst for urea synthesis but also elucidates the electronic mechanisms underlying potential-dependent catalytic activity.