Study the single-atom Mn-doped catalysts on boron nitride sheet surface as cathode for oxygen reduction reaction in proton‐exchange membrane fuel cells

Abstract

An important subject in improvement of polymer electrolyte membrane fuel cells (FCs) is sluggish kinetics of cathodic oxygen reduction reaction (ORR). In present work, Mn-doped vacancy boron nitride nanosheet has been offered as a noble-metal-free and efficient electrocatalyst for ORR process in fuel cells employing DFT computation. It is discovered that adsorption energy (Eads) values on Mn–N active site of selected catalysts enhance in order of: H2O > H2O2 > O2 > OOH > OH > O. For all intermediates containing oxygen, there is almost a consistent trend in Eads alteration. A slight thermodynamic force drives H2O2 formation and considerable ones for reduction of OOH into O* (or to 2OH*) indicate that 4e− pathway is more useful compared to 2e− pathway. Besides, from thermodynamic point of view, final stage of reduction (OH* + H+ + e− → H2O + *) within the highest value of ΔG for Mn-doped vacancy BN catalyst is rate-determining step (RDS). A larger HOMO-LUMO gap or a manganese d-band center remote from Fermi level indicates that catalyst doesn't favor adsorption of oxygen-containing species, which in turn results in higher ORR performance.