Premium
Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN 4 Active Sites
Author(s) -
He Yanghua,
Shi Qiurong,
Shan Weitao,
Li Xing,
Kropf A. Jeremy,
Wegener Evan C.,
Wright Joshua,
Karakalos Stavros,
Su Dong,
Cullen David A.,
Wang Guofeng,
Myers Deborah J.,
Wu Gang
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202017288
Subject(s) - zeolitic imidazolate framework , active site , catalysis , chemistry , density functional theory , transition metal , thermal decomposition , selectivity , adsorption , metal , carbon fibers , materials science , inorganic chemistry , metal organic framework , computational chemistry , organic chemistry , composite number , composite material
We elucidate the structural evolution of CoN 4 sites during thermal activation by developing a zeolitic imidazolate framework (ZIF)‐8‐derived carbon host as an ideal model for Co 2+ ion adsorption. Subsequent in situ X‐ray absorption spectroscopy analysis can dynamically track the conversion from inactive Co−OH and Co−O species into active CoN 4 sites. The critical transition occurs at 700 °C and becomes optimal at 900 °C, generating the highest intrinsic activity and four‐electron selectivity for the oxygen reduction reaction (ORR). DFT calculations elucidate that the ORR is kinetically favored by the thermal‐induced compressive strain of Co−N bonds in CoN 4 active sites formed at 900 °C. Further, we developed a two‐step (i.e., Co ion doping and adsorption) Co‐N‐C catalyst with increased CoN 4 site density and optimized porosity for mass transport, and demonstrated its outstanding fuel cell performance and durability.