Lithium manganese phosphate-carbon composite as a highly active and durable electrocatalyst for oxygen reduction reaction

Development of Pt-free electrocatalysts for oxygen reduction reaction (ORR) is one of the most important tasks for fuel cell commercialization. Various Mn compounds have been proposed as catalysts for ORR, but poor activity and stability necessitate further advances for their practical utilization. In this study, we demonstrate a lithium manganese phosphate-carbon composite (LMP-C) as a highly active and durable electrocatalyst for ORR in alkaline medium. LMP-C, synthesized by the solid-state method, exhibited significantly enhanced electrical conductivity and electrochemical properties, which led to a substantial increase in ORR performance. Comparison between LMP-C and the manganese phosphate-carbon composite, based on various physicochemical characterizations, revealed a high preference for the formation of the Mn3+ state on the surface of LMP-C that resulted in effective charge transfer during oxygen reduction. Moreover, the excellent stability of LMP-C was confirmed by carrying out 3000 cycles of the accelerated durability test, in which no drop in ORR performance was observed.