Electrocatalytic activity and structural transformation of Ca2Sr2Mn2MO10-δ (M\u2009=\u2009Fe, Co)

Abstract

The structural transformation between Ca2Sr2Mn2FeO10-δ and Ca2Sr2Mn2CoO10-δ and the enhancement in electrocatalytic activity is reported. Ca2Sr2Mn2FeO10-δ has a structure where corner-sharing (Mn/Fe)O6 octahedra form triple-layered stacks and Ca/Sr are located in spaces within and between the stacks. The incorporation of cobalt results in Ca2Sr2Mn2CoO10-δ, which has a greater concentration of oxygen vacancies and a quasi-one-dimensional structure, consisting of chains of CoO6–MnO6–MnO6–CoO6 polyhedra with distorted trigonal prismatic and octahedral geometry. Detailed investigation of the electrocatalytic activities of these materials indicates that these compounds are able to catalyze both half reactions of water splitting, namely, hydrogen-evolution reaction (HER) and oxygen-evolution reaction (OER). Ca2Sr2Mn2CoO10-δ shows enhanced electrocatalytic properties compared with Ca2Sr2Mn2FeO10-δ. The former material exhibits lower overpotential and greater electrochemically active surface area, as well as faster kinetics for both HER and OER processes.