Microcystin toxicosis in cattle due to overgrowth of blue-green algae.

Abstract

This article presents a facile and effective approach to activate the bifunctionality of calcium-manganese perovskites toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). We substituted Nb into the Mn site of CaMnO₃ (CMO) and treated the material with H₂. The as-obtained CaMn_0.75Nb_0.25O_3-δ (H₂-CMNO) displays the same structure as that of CMO, and compared to that of CMO, H₂-CMNO exhibits significantly improved OER performance, including a lower overpotential, a reduced Tafel slope, a higher mass activity, and enhanced stability. In addition, the ORR performance of H₂-CMNO is also greatly enhanced, relative to CMO, with a higher ORR activity and a more efficient electron-transfer pathway. H₂-CMNO shows an even higher activity-per-catalyst cost and superior stability than that of state-of-the-art materials, such as IrO₂ and Pt/C. This great enhancement in ORR and OER activity of H₂-CMNO is attributed to several factors, including phase stabilization, optimized e_g filling, better OH^- adsorption, and improved electrical conductivity.