Oxygen Defect‐Rich WO₃₋<i>_x</i>–W₃N₄ Mott–Schottky Heterojunctions Enabling Bidirectional Catalysis for Sulfur Cathode

Abstract

Abstract The serious shuttle effect and intrinsically sluggish oxidation–reduction reaction kinetics of polysulfides severely hinder the practical commercialization of lithium–sulfur (Li–S) batteries. Herein, oxygen‐defect‐rich WO 3− x –W 3 N 4 Mott–Schottky heterojunctions are designed as efficient catalysts. Based on theoretical calculations and comprehensive experimental characterization, WO 3− x –W 3 N 4 exhibits a lower free energy change (1.03 eV) and Li 2 S decomposition energy barrier (0.92 eV) than WO 3 and W 3 N 4 , which significantly enhances the sulfur reduction reaction (SRR) activity. Furthermore, a relationship between the catalytic activity and the energy gaps in the d and p bands centers (Δ d–p ) is also established, with the low Δ d–p of the heterojunction leading to a lower antibonding state energy, which promotes electron transfer and interfacial redox kinetics. Oxygen vacancies can improve the catalytic effect without affecting adsorption. Hence, the Li–S battery using WO 3− x –W 3 N 4 @CC/S exhibited outstanding rate and duration performance (913.9 mAh g –1 at 2 C, stable 400 cycles at 1 C). Impressively, the battery achieves a high areal capacity of 5.0 mAh cm −2 under a high sulfur loading of 4.98 mg cm −2 .