Structural and interfacial engineering of well-defined metal-organic ensembles for electrocatalytic carbon dioxide reduction

Pulse Electrolysis Turns on CO2 Methanation through N-Confused Cupric Porphyrin

Breaking the D4h symmetry in the square-planar M-N4 configuration of macrocycle molecular catalysts has witnessed enhanced electrocatalytic activity, but at the expense of electrochemical stability. Herein, we hypothesize that the lability of the active Cu-N3 motifs in the N-confused copper (II) tetraphenylporphyrin (CuNCP) could be overcome by applying pulsed potential electrolysis (PPE) during electrocatalytic carbon dioxide reduction. We find that applying PPE can indeed enhance the CH4 selectivity on CuNCP by 3 folds to reach the partial current density of 170 mA cm-2 at >60 % Faradaic efficiency (FE) in flow cell. However, combined ex situ X-ray diffraction (XRD), transmission electron microscope (TEM), and in situ X-ray absorption spectroscopy (XAS), infrared (IR), Raman, scanning electrochemical microscopy (SECM) characterizations reveal that, in a prolonged time scale, the decomplexation of CuNCP is unavoidable, and the promoted water dissociation under high anodic bias with lowered pH and enriched protons facilitates successive hydrogenation of *CO on the irreversibly reduced Cu nanoparticles, leading to the improved CH4 selectivity. As a key note, this study signifies the adaption of electrolytic protocol to the catalyst structure for tailoring local chemical environment towards efficient CO2 reduction.

Modulating the Asymmetric Atomic Interface of Copper Single Atoms for Efficient CO2 Electroreduction

Cu single-atom catalysts (Cu SACs) have been considered as promising catalysts for efficient electrocatalytic CO₂ reduction reactions (ECRRs). However, the reports on Cu SACs with an asymmetric atomic interface to obtain CO are few. Herein, we rationally designed two Cu SACs with different asymmetric atomic interfaces to explore their catalytic performance. The catalyst of CuN₃O/C delivers high ECRR selectivity with an FE_CO value of above 90% in a wide potential window from -0.5 to -0.9 V vs RHE (in particular, 96% at -0.8 V), while CuCO₃/C delivers poor selectivity for CO production with a maximum FE_CO value of only 20.0% at -0.5 V vs RHE. Besides, CuN₃O/C exhibited a large turnover frequency (TOF) up to 2782.6 h^-1 at -0.9 V vs RHE, which is much better than the maximum 4.8 h^-1 of CuCO₃/C. Density functional theory (DFT) results demonstrate that the CuN₃O site needs a lower Gibbs free energy than CuCO₃ in the rate-determining step of CO desorption, leading to the outstanding performance of CuN₃O/C on the process of ECRR-to-CO. This work provides an efficient strategy to improve the selectivity and activity of the ECRR via regulating asymmetric atomic interfaces of SACs by adjusting the coordination atoms.