Hierarchical Carbon/Metal Nanostructure with a Combination of 0D Nanoparticles, 1D Nanofibers, and 2D Nanosheets: An Efficient Bifunctional Catalyst for Zinc‐Air Batteries

Abstract

AbstractMulti‐dimensional hierarchical nanostructures can efficiently promote the mass transportation and electron transfer of electrocatalysts, which can boost the electrocatalytic performance. In this study, we report the design of a hierarchical carbon/metal nanostructure (Co@CNFs) with the combination of 0D cobalt metal nanoparticles, 1D carbon nanofibers, and 2D carbon nanosheets as a bifunctional oxygen reduction/evolution reaction (ORR/OER) catalyst. The Co@CNF catalysts are prepared by using a facile approach of combining electrospinning, impregnation growth of ZIF‐67 nanosheets, and high‐temperature carbonization. Through rationally optimizing the synthesis conditions, including the chemical concentration and carbonization temperature, the optimal catalyst of Co@CNFs‐50‐800 features a hierarchical structure of continuous carbon nanofibers (CNFs)‐anchored carbon nanosheets wrapping Co nanoparticles, which holds decent catalytic activities in term of a half‐wave potential of 0.8 V for the ORR and a potential of 1.54 V for the OER at 10 mA cm−2. A rechargeable Zn‐air battery is set up using the catalyst as the air cathode, which exhibits a high specific capacity of 809 mAh g−1 and a peak power density of 165.5 mW cm−2, as well as a good durability up to 1000 charging‐discharging cycles (>160 h), which is even better than the benchmark Pt/C+RuO2 catalyst. This study provides a rational strategy to design hierarchically nanostructural catalysts to boost the mass transportation and electron transfer of electrocatalytic reactions.