High-performance single atom bifunctional oxygen catalysts derived from ZIF-67 superstructures

Strong metal-support interaction promoted scalable production of thermally stable single-atom catalysts

“…2c). The absorption edge energies of Ru 1 /MAFO-900 and Ru/MAFO-500 were identical and matched that for RuO 2 , consistent with the presence of Ru 4+ species observed by XPS; however, the X-ray absorption near-edge structure (XANES) of Ru 1 /MAFO-900 differed from that of Ru/MAFO-500 and RuO 2 , i.e., Ru atoms in Ru 1 /MAFO-900 are in a different coordination environment to those in RuO 2 NPs/aggregates 48,49 . Fourier transforms of the corresponding extended X-ray absorption fine structure (EXAFS) reveal two well-defined coordination shells at~1.97 and 3.54 Å for RuO 2 and Ru/MAFO-500 associated with Ru-O and Ru-O-Ru scattering contributions, respectively ( Fig.…”

Rational Design of Hierarchical, Porous, Co‐Supported, N‐Doped Carbon Architectures as Electrocatalyst for Oxygen Reduction

“…According to the literature, Py‐N and Gra‐N can effectively boost oxygen adsorption to reduce the ORR overpotential because of their excellent electron‐accepting abilities, and Py‐N and Gra‐N can effectively boost oxygen adsorption to lower the ORR overpotential because of their excellent electron‐accepting abilities . In addition, some of Py‐N and Pyr‐N atoms can serve as coordination sites for Co in the form of N‐coordinated Co structures: Co–N x ( x =2 and 4), as previously identified by X‐ray absorption spectroscopy and Mössbauer spectroscopy . In agreement with experimental studies, DFT calculations suggested that Co–N x has a lower energy barrier for oxygen dissociation and thus acts as active site in the catalytic ORR process of Co–N–C‐based catalysts …”

“…[31] In addition, some of Py-N and Pyr-N atoms can serve as coordination sites for Co in the form of N-coordinated Co structures: Co-N x (x = 2a nd 4), as previously identified by X-ray absorption spectroscopy and Mçssbauer spectroscopy. [19,32] In agreement with experimental studies, DFT calculations suggested that Co-N x hasalower energy barrier for oxygen dissociation and thusa cts as active site in the catalytic ORR process of Co-N-C-based catalysts. [10b, 11,29] As shown in Figure 4d,t he ratio of Py-N and Pyr-N in Co-NOPC rapidlyd ecreasesw ith increasing annealing temperature.…”

“…After thermal treatment at 500 °C, the crystal surface (Figure d–f) is no longer smooth, and the hierarchically ordered macro‐/micropores transform into an interconnected carbon skeleton. The relatively disordered carbon phase (Figure f) implies that abundant defects, such as vacancies, dislocations, and shear defects, which favor ORR catalysis, exist in the carbon structure . The energy‐dispersive X‐ray spectroscopy (EDS) mapping in Figure g demonstrates that no dramatic migration and aggregation of Co metal occurs after pyrolysis, which is attributed to the in situ conversion of Co–N coordination under mild conditions .…”

“…The relatively disordered carbon phase ( Figure 2f)i mplies that abundant defects, such as vacancies, dislocations, and shear defects, which favor ORR catalysis, exist in the carbon structure. [19] The energy-dispersive X-ray spectroscopy (EDS) mapping in Figure 2g demonstrates that no dramatic migration and aggregation of Co metal occurs after pyrolysis, which is attributed to the in situ conversion of Co-N coordination under mild conditions. [20] For comparison, the morphologies of conventional ZIF-67 and carbonized derivative Co-NC were also investigated ( Figure S3 in the SupportingInformation).…”