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

• ZIF-67-derived CoO@GC/WO 3 @CL is used as a bifunctional catalyst for the first time. • Intra-particle maturation of WO 3 from microrod to nanosphere forms more O-vacancies. • PVP-derived CL protects Co 2+ (CoOOH) and O-vacancies to stabilize ORR/OER activities. • Cooperation between WO 3 and Co 2+ boosts electron transfer to promote 4e − ORR pathway. • Interaction between CoOOH (Co 3+ ) and O-vacancies (WO 3 ) promotes O 2 generation (OER). 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, WO 3 -anchored ZIF-67-derived CoO@graphitized carbon is wrapped by a thin carbon-layer to obtain CoO@GC/WO 3 @CL catalysts. The well-crystallized WO 3 nanospheres are evolved from WO 3 microrods via an intra-particle maturation. For ORR, the peak-potential of CoO@GC/WO 3 @CL-800 (800 ℃) (0.81 V vs. RHE) is higher than that of Pt/C (0.79 V). Synergies between WO 3 (oxygen vacancies) and CoO (Co 2+ ) improve mass/charge transfer to boost the 4e − pathway. For OER, CoO@GC/WO 3 @CL-800 has a lower overpotential (330 mV) than RuO 2 (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 H 2 O-oxidation to boost the O 2 -generation. A relatively low ΔE [E j=10 (OER)-E 1/2 (ORR)] of 0.72 V confirms the highly-stable ORR/OER activities of CoO@GC/WO 3 @CL-800, which obtains a higher power density (138 mW cm −2 ) than Pt/C + RuO 2 cathode in primary ZABs. This study indicates a new direction to build a multilayer-structured ORR/OER catalyst by using ZIFs as templates.