Oxygen Reduction Reaction on Doped Lanthanum Chromate Perovskites

Abstract

The oxygen reduction reaction (ORR) plays a pivotal role in fuel cell technology and the generation of clean oxidizing agents. This reaction can proceed via two distinct pathways. The complete ORR pathway involves reducing oxygen to water through a four-electron transfer process. Alternatively, a two-electron transfer path- way leads to the partial reduction of oxygen, yielding hydrogen peroxide (H2O2) as the product. The perovskite CaSnO3 has demonstrated stability and selectivity in electrochemically oxidizing H2O to H2O2. In a similar vein, other perovskite oxides have demonstrated good selectivity in the complete ORR. Their catalytic perfor- mance can be analyzed through microkinetic analysis and the application of scaling relations. In this study, we explore a series of perovskites based on LaMO3, where ’M’ denotes a combination of Cr, Co, and Ni. Changes in the type and concentra- tion of doping lead to contraction in the perovskite lattice, along with alterations in B-O-B bond length and angle. These structural changes contribute to differences in their catalytic performance towards the ORR. The inclusion of Co in the catalyst tends to favor the four-electron ORR pathway, while the addition of Ni shows a predilection for the two-electron pathway.