Efficient C−N Coupling via Oxidation State Inversion in Asymmetric Copper–Zinc Amorphous-Like Atomic Clusters Driving Photoelectrocatalytic Urea Synthesis

Photoelectrochemical (PEC) coupling of CO₂ and nitrate presents a sustainable strategy for urea synthesis under ambient conditions. However, the complexity of the proton-coupled electron transfer process restricts the selective formation of the key intermediates, impeding efficient C–N coupling. Here, copper–zinc amorphous-like ultra-small atomic clusters are developed for efficient urea synthesis. The atomically disordered arrangement in the amorphous-like structure breaks the periodicity constraints of crystalline counterpart, enabling asymmetric Cu^δ+–Zn^δ+ coordination featuring oxidation state inversion, where the Cu oxidation state elevates within a narrow valence range (0 < δ < 1) and the Zn oxidation state reduces compared to the crystalline counterpart. More importantly, the oxidation state inversion generates electron-deficient Cu centers that stabilize the formation of new *NO intermediates, which are identified as a key intermediate that facilitates coupling with *CO species adsorbed on the electron-rich Zn sites, effectively reducing the activation barrier for C–N coupling involved in the formation of *OCNO. Under simulated AM 1.5G irradiation, the PEC system demonstrated well-balanced performance, achieving a high production rate of 64.03 mmol g⁻¹ h⁻¹ at a low external potential of −0.1 V versus the reversible hydrogen electrode, with a corresponding Faradaic efficiency of 46.60% and an incident photon-to-current conversion efficiency of 17.6% at monochromatic illumination.