Engineering heterointerfaces coupled with oxygen vacancies in lanthanum–based hollow microspheres for synergistically enhanced oxygen electrocatalysis

The development of high–efficiency and low–cost bifunctional oxygen electrocatalysts is critical to enlarge application of zinc–air batteries(ZABs). However, it still remains challenges due to their uncontrollable factor at atomic level during the catalysts preparation, which requires the precise regulation of active sites and structure engineering to accelerate the reaction kinetics for both oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). Herein, a novel Co–doped mixed lanthanum oxide and hydroxide heterostructure(termed as Co–La MOH|OV@NC) was synthesized by pyrolysis of La–MOF–NH2with spontaneous cobalt doping. Synergistic coupling of its hollow structure, doping effect and abundant oxygen vacancies creates more active sites and leads to higher electroconductivity, which contribute to the better performance. As employed as a bifunctional oxygen electrocatalyst, the resulting 3 Co–La MOH|OV@NC exhibits superior electrocatalytic activity for both ORR and OER. In assembled ZAB, it also demonstrates an excellent power density of 110.5 m W cm-2, high specific capacity of 810 m Ah gZn-1, and good stability over 100 h than those of Pt/C + RuO2. Density functional theory(DFT) calculation reveals that the heterointerfaces coupled with oxygen vacancies lead to an enhanced charge state and electronic structure, which may optimize the conductivity, charge transfer, and the reaction process of catalysts.This study provides a new strategy for designing highly efficient bifunctional oxygen electrocatalysts based on rare earth oxide and hydroxides heterointerface.