N, S, P co-doped graphene-like carbon nanosheets developed via in situ engineering strategy of carbon pz-orbitals for highly efficient oxygen redox reaction

Abstract Multi-heteroatom doped carbon materials without any potential threat of transition metal contaminants are ideal candidates to replace precious metals for the electrocatalysis of energy conversion. However, tuning their bifunctionality for oxygen redox reaction (oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)) is still a critical issue. Herein, N, S, P co-doped graphene-like carbon nanosheets (NSP/C) were developed via a bottom-up doping strategy with NaCl as template using a new precursor of N, S co-containing copolymer of 2, 6-Diacetylpyridine (DAP, N source) and 2-aminophenyl disulfide (APD, S source), and mixed with a P source of phosphonitrilic chloride trimer (PCT). The optimized NSP/C derived from DAP/APD and PCT with the mass ratio of 1:1 presents an ultra-high surface area of 1209 m2·g−1, around 3.0 nm in the thickness of nanosheets, resulting in a high half-wave potential up to 0.88 V vs. RHE for ORR and a low overpotential down to 0.35 V vs. RHE at 10 mA cm−2 for OER, as well as remarkable stability, while its overall oxygen redox activity is 0.70 V in 0.1 M KOH. And the performance was also proved by a practical rechargeable zinc-air battery with a maximum power density output of 156 mW·cm−2, which is better than that of the same-loading commercial catalysts of Pt/C and IrO2 (mixed with a mass ratio of 1:1). The high bifunctionality is strongly relied on the energy increase of pz-orbitals of carbon atoms in active sites comprising the specific ratio of graphitic N, thiophenic S and graphitic P dopants obtained from the new precursor.