Recently, the State Key Laboratory of Catalysis of Dalian Institute of Chemical Physics, Chinese Academy of Sciences Bao Xinhe and Wang Guoxiong team made new progress in the research of high-efficiency carbon dioxide electrocatalysis. The relevant results were published in Energy Environ. Sci. .
The carbon dioxide electrocatalytic reduction reaction (CO2RR) can simultaneously achieve the conversion and utilization of carbon dioxide and the efficient storage of renewable clean electric energy, which is conducive to the construction of a sustainable carbon resource recycling network. In recent years, the research team has developed a unique perspective from the perspective of catalysis. In-depth CO2 electrocatalytic reduction studies have yielded a series of research results in nano-Pd-based catalysts, metal-oxide interfaces, etc., which have significantly improved the selectivity, activity, and stability of electrocatalytic reduction of CO2 (J. Am. Chem. Soc., Chem. Sci., J. Am. Chem. Soc., ACS Catal., Angew. Chem. Int. Ed.).
Transition metal-nitrogen-carbon composites are a class of electrocatalytic materials promising alternatives to precious metals. The research team recently focused on the controlled preparation of such materials and their electrocatalytic properties (Energy Environ. Sci., Nano Energy, ACS Catal). Previous studies have shown that the transition metal-nitrogen-carbon composites can reduce CO2 by electrocatalytic reduction to produce CO, but as the overpotential increases, the competitive hydrogen evolution reaction (HER) current increases sharply, resulting in a rapid decline in CO Faradaic efficiency. It is difficult to obtain high CO current density. Therefore, obtaining high CO2RR current density and faradaic efficiency at the same time is an important challenge for transition metal-nitrogen-carbon composites.
In this study, the team succeeded in preparing a porous Ni-N-doped porous carbon material that is monodispersed by pyrolyzing a zinc/nickel bimetallic zeolite imidazole skeleton (ZIF-8). The loading capacity of Ni species is up to 5.44wt%. On this Ni-N catalyst, the CO-Faraday efficiency is maintained between 92.0% and 98.0% within a wide potential range of -0.53V to -1.03V (vs. RHE). The current density increases with the increase of overpotential and reaches 71.5±2.9mA/cm2 at -1.03V (vs. RHE). The characterization and comparative experiments show that the coordination unsaturated Ni-N is the active site; Density functional theory calculation It is further revealed that CO2RR is more likely to occur in the NiN2V2 (V stands for vacancy) than HER. It is speculated that NiN2V2 may be the active site of CO2RR. Therefore, the high-load coordination of the unsaturated Ni-N active sites simultaneously achieves a high current density of CO2RR and Faraday efficiency, breaking the 'saw' effect limit of CO2RR selectivity and reaction rate on transition metal-nitrogen-carbon composites.
The above research work has been funded by the National Natural Science Foundation of China, the National Key R&D Program, the DMTO, and the pilot projects of the Chinese Academy of Sciences.
