Rare-Earth Lanthanum Tailoring Mott–Schottky Heterojunction by Sulfur Vacancy Modification as a Bifunctional Electrocatalyst for Zinc–Air Battery

Abstract

Zinc–air battery (ZAB) has considerable potential to be applied in the energy storage field. The main commercial electrocatalysts are Pt/C and RuO2, which are expensive and cannot possess good bifunctional electrocatalytic activities including oxygen reduction reaction and oxygen evolution reaction. Herein, the rare-earth metal lanthanum is first constructed to be a Mott–Schottky heterojunction, and the S vacancy is introduced into the Mott–Schottky heterojunction. The so-obtained La/La2O2S1−x shows excellent bifunctional electrocatalytic activity with ΔE of 0.68 V, which is superior to La/La2O2S without S vacancies and the commercial Pt/C + RuO2 system. In addition, the La/La2O2S1−x is assembled into ZABs, showing a high open power density of 212 mW cm−2, and a large specific capacity of 707 mAh g−1, as good cycle stability. The density functional theory calculations reveal the tailoring effect of S vacancy on the Schottky barrier to control the electron transfer concentration and ameliorate over-strong adsorption, which blocks the reflux of electrons and promotes the unidirectional flow of electrons. In addition, the S vacancy modulates the electron cloud of La-4f orbit and makes the electrocatalytic pathway closer to the ideal pathway.