Eggshell‐Like Carbon Microspheres with Curvature Scheme: Distorted Energy Band and Atomic Charge Waves‐Driven High Performance for Zinc–Air Battery

Abstract

AbstractA metal‐free nanocarbon with an eggshell structure is synthesized from chitosan (CS) and natural spherical graphite (NSG) as a cathode electrocatalyst for clean zinc‐air batteries and fuel cells. It is developed using CS‐derived carbons as an eggshell, covering NSG cores. The synthesis involves the in situ growth of CS on NSG, followed by ammonia‐assisted pyrolysis for carbonization. The resulting catalyst displays a curved structure and completely coated NSG, showing superior oxygen reduction reaction (ORR) performance. In 1 M NaOH, the ORR half‐wave potential reached 0.93 V, surpassing the commercial Pt/C catalyst by 50 mV. Furthermore, a zinc‐air battery featuring the catalyst achieves a peak power density of 167 mW cm‐2 with excellent stability, outperforming the Pt/C. The improved performance of the eggshell carbons can be attributed to the distorted energy band of the active sites in the form of N‐C moieties. More importantly, the curved thin eggshells induce built‐in electric fields that can promote electron redistribution to generate atomic charge waves around the N‐C moieties on the carbon shells. As a result, the high positively charged and stable C+ sites adjacent to N atoms optimize the adsorption strength of oxygen molecules, thereby facilitating performance.