Tuning of Oxygen Reduction Pathways through Structural Variation in Transition Metal‐Doped Ba2In2O5

Abstract Oxygen reduction reaction (ORR) can take place either through a two‐electron pathway to form H 2 O 2 or through a four‐electron pathway to form H 2 O. Both the reactions are important in the respective fields, viz., H 2 O 2 production as well as fuel cell technology, and rational design of catalysts is mandatory to acquire high energy efficiency in both cases. Here, we report the structure‐electrochemical property correlation of a series of perovskite related brownmillerite compounds, Ba 2 In 0.75 M 0.25 O 5 (M=Mn/Fe/Co/Ni/Cu), synthesized by solid‐state method. On transition metal doping, octahedral distortions were observed, and the highly disordered material tends to follow the 4e transfer mechanism. More symmetrical structures followed the 2e pathway to form H 2 O 2 as the product with high peroxide selectivity. The distortion in the octahedral arrangement can be a descriptor to finetune the selectivity of the catalysts towards the 2e and 4e pathways of ORR.