image: Fig. 1. Theoretical Prediction and Structural Identification of SbNx Configuration. (a) Local coordination environment, (b) PDOS diagram of the enveloped SbN5 stereoconfiguration. (c) Schematic of Sb-p and O-2p orbital hybridisation. (d) Orbital interactions between the Sb centres and ligands. (e) Differential charge distributions and corresponding Bader charge values for SbN4 and SbN5 configuration. (f) TEM image and corresponding selected area electron diffraction, HRTEM image, (g) HAADF-STEM image and statistical analysis of the distance between Sb atoms, (h) EDX elemental mapping for SbAC-NC-5. (i) The SXAS spectra of N K-edge, (j) XANES spectra and white line inset, and (k) fitting EXAFS of Sb K-edge for SbAC-NC-5 and other samples.
Credit: ©Science China Press
The construction of cathode catalysts that combine high activity and stability is essential for improving the energy conversion efficiency of metal-air batteries and fuel cells. Single-atom catalysts (SACs) provide a novel solution to the challenge of slow oxygen reduction reaction (ORR) kinetics by atomic-level active sites and precisely tunable electronic configurations. Unlike transition metals, the relatively inert Sb centers can be precisely tuned by coordination engineering to exhibit strong affinity. However, the strength of the Sb-N bond is a fundamental determinant of stability. This new study, led by Professor We Zhang in the School of Materials Science and Engineering, has successfully achieved precise tuning of the first coordination shell environment of Sb centres in SbAC-NC-x catalysts after varying degrees of NH4Cl gas-phase etching. Remarkably, the catalyst with an encapsulated SbN5 stereoconfiguration exhibited an extremely high half-wave potential (E1/2 = 0.908 V) in an alkaline medium, and the E1/2 decreased by only 11 mV after accelerated durability tests (150,000 cycles), which demonstrated that the catalyst possessed excellent long-term durability. Combining in-situ techniques and theoretical calculations, they fully verified that the orbital stabilisation effect of the SbN5 stereoconfiguration mitigated the *OH steric hindrance on the Sb centres. This phenomenon promoted the activation of the *OH state by preventing the interaction between the Sb centres and intermediates, thus accelerating the formation of *OOH. This study was supported by the National Natural Science Foundation of China.
Journal
Science Bulletin