High-valence single-atom catalysts (HVSACs) generally exhibit superior catalytic activity owing to the fast electron transfer efficiency between HVSACs and their supportive substrate. Nevertheless, the thermodynamically unstable HVSACs are prone to spontaneous aggregation during their conventional synthesis processes, largely limiting their practical application demanding long-term stability. Herein, we demonstrate a universal approach to synthesize stable HVSACs by incorporating high-electronegativity fluorine (F) atoms to directly coordinate with the targeted metal atoms (M) of HVSACs on nitrogen-carbon supports. As a result, an asymmetric planar M-N2F2 structure is introduced, which boosts asymmetric polarized spin between M and F atoms with M stabilized at their high-spin and high-valence state. Leveraging this motif, we further demonstrate its high universality as a promising synthetic approach by obtaining stable HVSACs for 22 individual metal elements. Using high-valence Mn single-atom as a model system, the resulting MnN2F2 catalyst exhibits not only high activity but also superior durability in both the oxygen reduction reaction (ORR) and practical Zn-air batteries, outperforming conventional MnN4 single atoms.
Qi et al. (Thu,) studied this question.