Efficient acidic oxygen evolution reaction electrocatalyzed by iridium-based 12L-perovskites comprising trinuclear face-shared IrO6 octahedral strings

Abstract

Abstract Development of cost-effective and highly active oxygen evolution catalysts operating well in acidic media is a critical challenge in proton exchange membrane water electrolysis. Herein, we present a class of iridium-based 12L-perovskites (Ba4MIr3O12; M = Pr, Bi, Nb) as novel low-iridium electrocatalysts for oxygen evolution reaction under acidic conditions. These 12L-perovskites contain trinuclear face-shared IrO6 octahedral strings—unique subunits that are not found in the previously-reported iridium-based electrocatalysts. The catalytic activities of 12L-perovskites (Ba4MIr3O12) are found to be related to the location of O 2p-band center, which is influenced by the B-site nonprecious element (i.e., Pr, Bi or Nb). Our experimental results show that Ba4PrIr3O12 is the most active electrocatalyst among the materials we synthesize, and contains 55% less iridium than the benchmark catalyst IrO2, while exhibiting higher catalytic activity. In the presence of Ba4PrIr3O12, transient leaching process of Ba and Pr takes place during electrochemical process, contributing to the surface reconstruction of the pristine catalysts. Further experimental results reveal that the formation of under-coordinated IrOx-rich surface and easier generation of active intermediate IrV are mainly responsible for the good activity of Ba4PrIr3O12.