Boosting the Ni-Zn interplay via O/N dual coordination for high-efficiency CO2 electroreduction

Design of supportive atomic sites with a controllably adjusted coordinating environment is essential to advancing the reduction of CO2 to value-added fuels and chemicals and to achieving carbon neutralization. Herein, atomic Ni (Zn) sites that are uniquely coordinated with ternary Zn (Ni)/N/O ligands were successfully decorated on formamide-derived porous carbon nanomaterials, possibly forming an atomic structure of Ni(N2O1)-Zn(N2O1), as studied by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. With the mediation of additional O coordination, the Ni-Zn dual site induces significantly decreased desorption of molecular CO. The NiZn-NC decorated with rich Ni(N2O1)-Zn(N2O1) sites remarkably gained >97% CO Faraday efficiency over a wide potential range of -0.8 to -1.1 V (relative to reversible hydrogen electrode). Density functional theory computations suggest that the N/O dual coordination effectively modulates the electronic structure of the Ni-Zn duplex and optimizes the adsorption and conversion properties of CO2 and subsequent intermediates. Different from the conventional pathway of using Ni as the active site in the Ni-Zn duplex, it is found that the Ni-neighboring Zn sites in the Ni(N2O1)-Zn(N2O1) coordination showed much lower energy barriers of the CO2 protonation step and the subsequent dehydroxylation step.