N- and S-doped porous carbon decorated with in-situ synthesized Co–Ni bimetallic sulfides particles: A cathode catalyst of rechargeable Zn-air batteries

A novel 3D composites comprising in-situ formed CoNi bimetallic sulfides particles (CoNi[email protected]) embedded in N, S-doped porous carbon was facilely constructed for the air cathode catalyst for Zn-air batteries. The synergistic interplay between N, S doped carbon matrix, the porous structure and the highly catalytic active cobalt nickel sulfides species contributes greatly to the excellent bifunctional catalytic activity both in the ORR and OER in 0.1 M KOH solution for the CoNi[email protected] catalyst. The ORR measurement results showed that the half-wave potential (0.82 V vs. RHE), current density (5.23 mA cm−2 at 0.2 V vs. RHE) of our sample were very close to that of Pt/C (0.82 V, 5.17 mA cm−2), meanwhile its stability and methanol tolerance were superior to Pt/C. The OER measurement results showed that the CoNi[email protected] catalyst exhibited a small overpotential (0.47 V vs. RHE) at 10 mA cm−2, close to that of RuO2 (0.39 V). Importantly, compared to the mixture of Pt/C and RuO2 cathodes, the rechargeable Zn-air battery based on CoNi[email protected] cathode exhibits smaller discharge/charge overpotential (0.85 V), higher power density (51.6 mW cm−2), higher voltaic efficiency (58.5%) at 10 mA cm−2 and an improved cycling stability over 3600 min.