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Fe and N Co-Doped Porous Carbon Nanospheres with High Density of Active Sites for Efficient CO₂ Electroreduction

Chen, Yubin, Zou, Liangliang, Liu, Hong, Chen, Chi, Wang, Qi, Gu, Meng, Yang, Bo, Zou, Zhiqing, Fang, Jianhui, Yang, Hui
Journal of physical chemistry 2019 v.123 no.27 pp. 16651-16659
X-ray absorption spectroscopy, active sites, carbon, carbon dioxide, carbon monoxide, catalysts, catalytic activity, cobalt, desorption, electrochemistry, iron, nanospheres, nitrogen, silica, transmission electron microscopy
To enhance the electrocatalytic performance of transition metal and nitrogen codoped carbon (M–N–C) for the CO₂ electroreduction reaction, we present a Fe and N codoped porous carbon nanosphere (Fe–N–PC) with a high density of single-atom iron active sites and a few Fe clusters, as indicated by high-resolution TEM and EXAFS, using SiO₂ as the protecting shell to restrict isolated Fe atoms and to trap the volatile N-containing species. The Fe doping content can reach as high as 3.9 wt %. The Fe–N–PC catalyst exhibits an excellent performance for converting CO₂ to CO with high Faradaic efficiency (∼90%) and remarkable partial CO current density (11.44 mA cm–²) at −0.49 V. Probing analysis and selective chemical modification reveal that both Fe atom and ortho-C of N atoms play a synergetic role in enhancing CO₂RR activity. DFT calculations reveal that the presence of amorphous Fe clusters can facilitate the desorption of CO from the surface of the catalyst, thus further improving the CO₂RR activity. This work presents a general strategy to synthesize advanced M–N–C material with high density of single atom active sites, which could be used as an efficient electrocatalyst for CO₂RR, ORR et al.