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Hefei Research Institute develops iron monoatomic catalyst to realize electrocatalytic nitrogen fixation to ammonia
[ Instrument R & D of Instrumentation Network ] Recently, the Center for Environmental and Energy Nanomaterials, Institute of Solid Physics, Hefei Academy of Material Sciences, Chinese Academy of Sciences has made new progress in electrocatalytic nitrogen reduction at room temperature and pressure The single atom catalyst realizes high-efficiency electrocatalytic reduction of nitrogen to ammonia. Relevant research results were published in the full-text in the international journal "Angewandte Chemie International Edition".
Monoatomic catalysts have the greatest mass catalytic activity and adjustable coordination electron structure, and have been widely used in thermal catalysis, photocatalysis and electrocatalysis. Unlike other forms of catalysts, the catalytic activity of a single-atom catalyst depends on the nature of the single atom, the physicochemical properties of the support, and the form of coordination bonds that fix the single atom to the support. So far, various carbon-supported noble metal and transition metal monoatomic electrocatalysts have been reported. However, these monoatomic catalysts are almost always anchored to the carbon support through metal-nitrogen (or carbon) coordination bonds, so exploring other forms of coordination configurations to prepare monoatomic catalysts will be beneficial to enrich monoatomic catalysts. The types of catalyst families and expand their new catalytic functions and application fields.
In recent years, ammonia synthesis at room temperature and piezoelectricity has been widely concerned by researchers, and may become an ideal ammonia synthesis process for the alternative energy-intensive Harper-Bosch industrial method. The monoatomic catalysts for electrocatalytic synthesis of ammonia reported to date include Au, Ru, Mo, Cu, Fe, and Co monoatomic catalysts anchored by metal-nitrogen on a nitrogen-containing carbon support, and anchored by metal-carbon bonds on graphyne Mo single atom catalyst fixed on carbon support. In addition, for all reported single-atom catalysts, the carbon support is almost prepared by carbon conversion of metal-organic frameworks (MOFs) or organic molecules, resulting in an increase in mass production costs. Biomass-based precursors are cheap, rich in resources, and easily available. It is very advantageous as a carbon carrier for large-scale synthesis of single-atom catalysts. More importantly, the surface of biomass precursors (such as chitin, chitosan, cellulose, hemicellulose, and lignin) is rich in nitrogen and oxygen functional groups, which is convenient for adjusting the adsorption activity of metal ions, and then through nitrogen and oxygen Site bonds controllably anchor a single atom to a carbon support to form a new type of catalytically active coordination configuration.
Based on this, the research group innovatively used oxygen-rich functional group and nitrogen-free lignocellulose as a precursor for Fe3 + adsorption. During the carbothermal reduction process, the Fe-O coordination structure (Fe- (O-C2) 4) An iron single atom is anchored to a carbon support (Fe-SAs / LCC). The application of nitrogen-free lignocellulose also allows researchers to study the catalytic properties of Fe-O coordination structures without interference from other coordination structures (especially Fe-Nx coordination structures). The results show that the Fe-SAs / LCC (Fe mass fraction of 0.60wt.%) Supported on the carbon cloth electrode can obtain ammonia yield and Faraday efficiency of 32.1 μg h-1 in 0.1 M KOH electrolyte. mg-1 (5350 μg h-1 mgFe-1) and 29.3%. In order to verify the effect of nitrogen mass transfer on the electrocatalytic nitrogen reduction reaction, the researchers loaded Fe-SAs / LCC on the glassy carbon electrode and obtained 307.7 μg h-1 mg-1 (51283 μg h-1 mgFe-1) The ultra-high ammonia yield and Faraday efficiency close to the record (51.0%). This research work provides new ideas for the design and development of high-performance monoatomic electrocatalysts.
This work was supported by the International Cooperation Project of the National Natural Science Foundation of China and the Innovation Research Team of the Chinese Academy of Sciences.