Microrods-evolved WO3 nanospheres with enriched oxygen-vacancies anchored on dodecahedronal CoO(Co2+)@carbon as durable catalysts for oxygen reduction/evolution reactions

Oxygen reduction/evolution reactions (ORR/OER) play the vital roles in energy-conversion devices, especially for Zn-air batteries (ZABs). However, it is always a challenge to explore a stable bifunctional catalyst. Here, WO3-anchored ZIF-67-derived CoO@graphitized carbon is wrapped by a thin carbon-layer to obtain CoO@GC/WO3@CL catalysts. The well-crystallized WO3 nanospheres are evolved from WO3 microrods via an intra-particle maturation. For ORR, the peak-potential of CoO@GC/WO3@CL-800 (800 ?) (0.81 V vs. RHE) is higher than that of Pt/C (0.79 V). Synergies between WO3 (oxygen vacancies) and CoO (Co2+) improve mass/charge transfer to boost the 4e(-) pathway. For OER, CoO@GC/WO3@CL-800 has a lower overpotential (330 mV) than RuO2 (490 mV) at 10 mA cm(-2). The O-2 evolution rate can reach 0.125 mmol s(-1) with a high Faraday efficiency of 96.7 %. Cooperation between CoOOH and oxygen vacancies promotes the H2O-oxidation to boost the O-2-generation. A relatively low delta E [E-j=10(OER)-E-1/2(ORR)] of 0.72 V confirms the highly-stable ORR/OER activities of CoO@GC/WO3@CL-800, which obtains a higher power density (138 mW cm(-2)) than Pt/C + RuO2 cathode in primary ZABs. This study indicates a new direction to build a multilayer-structured ORR/OER catalyst by using ZIFs as templates.

Automated summary

This study successfully constructs a multilayer-structured ORR/OER catalyst using ZIFs as templates, and achieves higher battery performance. The CoO@GC/WO3@CL-800 catalyst exhibits higher activity and stability in oxygen reduction and oxygen evolution reactions, making it more effective than traditional Pt/C + RuO2 cathode.