Surface-Confined Polymerization to Construct Binary Fe3n/Co-N-C Encapsulated Mxene Composites for High Performance Zinc-Air Battery

Abstract

2D MXenes (transition metal carbides, Ti 3 C 2 T x ) with large surface area and metallic conductivity are widely used as supporters in catalysts. Unfortunately, the single MXene sheets would deteriorate in the presence of oxygen and water, which is almost the same as the environment of oxygen reduction reaction (ORR). Herein, an “armor” was constructed to encapsulate the oxidizable MXene by a confined in-situ oxidative polymerization strategy, employing the electrostatic interaction between the exfoliated MXene sheets (negatively charged) and oxidant (Fe 3+ , positively charged). The ultra-dispersed binary Fe 3 N and Co sits coupled with the large surface area MXene supporter synergy to endow more exposed active sites, meanwhile, the density functional theory (DFT) studys reveal that a moderate binding strength between the intermediates and the binary active sites was effectively modulated to enhance the ORR performance. The synthesized Fe 3 N/Co-N-C@MXene exhibits an impressive half-wave potential (E 1/2 , 0.871V) and a lower Tafel slope of 52.56 mV dec -1 than that of Pt-C-20% (74.89 mV dec -1 ). The Fe 3 N/Co-N-C@MXene based ZAB exhibits a four times higher peak power density (189.16 mW cm -2 ) than the Pt-C-20% based ZABs and superior cycle stability within 320 h. Furthermore, the assembled flexible ZABs shows high flexibility and stability in different bending scenarios.

Keywords: MXene, Ultra-dispersed, Binary catalyst, ORR, Zn-air batteries.