Reconstructing bridging carbon atoms (from sp3-C to sp2-C) of pyrolytic N-doped carbon to enhance oxygen reduction reaction
The development of new regulation strategy for constructing functional carbon skeletons is a standing challenge for oxygen reduction reaction (ORR). Herein, the locally ordered graphene microcrystals with suitable N -sites derived from glucose are synthesized under the assistance of low melting point zinc molten salt . Utilizing the structural features of graphene microcrystals (“house of cards” model), the work function of carbon skeleton is reduced after inducing the conversion of bridging sp 3 -C to bridging sp 2 -C (ratio of sp 2 -C to sp 3 -C increases from 3.75 to 7.41). The lower work function of locally ordered microarchitectures decreases the long-range electron transfer barrier in outer-Helmholtz plane. And the synergy between pyridinic N and graphitic N is beneficial for enhancing short-range electron transfer process in inner-Helmholtz plane. After rearrangement of carbon skeletons, the half-wave potential can increase from 0.846 V to 0.874 V, and the HO 2 – by-product yield decreases from 31.5 % to 6.9 %. Furthermore, the discharge voltage of locally ordered microarchitecture (1.31 V) at 10 mA cm −2 can surpass the commercial Pt/C (1.25 V) in Zn-air battery devices. In brief, it provides a new direction of structure design for carbonaceous catalysts.
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