Se-functionalized metal-free catalysts rich in sp³-hybridized carbon enable efficient oxygen electroreduction

Carbon-based metal-free materials are emerging as leading candidates to replace noble-metal catalysts in the oxygen reduction reaction (ORR). Herein, we introduce a facile secondary carbonation technique for fabricating Se and N co-doped metal-free catalysts using a zeolite imidazole framework (ZIF-8) as the precursor. The optimal electrocatalyst, designated SeNC-900, exhibited good ORR performance under both alkaline and acidic conditions, with half-wave potentials of 0.864 V and 0.731 V (vs. RHE), respectively. Density functional theory (DFT) calculations reveal that the enhanced activity of SeNC-900 originates from Se doping, which triggers an increase in the intrinsic defects of sp³-hybridized C. Concurrently, the sp³-hybridized C, in concert with Se dopant, modulates the electronic structure of the active C atoms. This work not only underscores the significance of tuning the electronic structure to boost catalytic performance by enriching intrinsic defects but also presents a fresh insight into the effect of heteroatom doping on carbon-based materials for electrocatalysis.