Sodium Borohydride-Induced Surface Modification of Manganese Oxides for Optimized ORR Active Electrocatalysts

Abstract

Introduction:

Manganese oxide octahedral molecular sieves (OMSs) are promising catalysts for oxygen reduction reactions (ORRs) due to their cost-effectiveness and durability. However, their practical application is hindered by inherent limitations, including low electrical conductivity and insufficient intrinsic catalytic activity.

Method:

To address these challenges, we employed a novel surface reduction etching treatment using sodium borohydride (NaBH₄) to optimize the oxygen vacancy content of OMS materials. This method involves immersing OMS samples in varying concentrations of NaBH₄ solution followed by vacuum annealing, leading to the controlled introduction of oxygen vacancies.

Results:

The NaBH₄ treatment significantly increased the number of oxygen vacancies on the OMS surface. These vacancies act as crucial active sites, facilitating the adsorption and dissociation of oxygen molecules, thereby improving ORR activity. Furthermore, the treatment was found to regulate the Mn³⁺/Mn⁴⁺ ratio on the nanorod surface, further promoting catalytic efficiency. Notably, the OMS material treated with 6mmol/L NaBH₄ exhibited a remarkable half-wave potential of 0.74 V in an alkaline medium of 0.1M KOH electrolyte, which is comparable to the state-of-the-art platinum catalyst (0.837 V).

Conclusions:

The optimized OMS materials exhibited significantly improved ORR performance compared to pristine OMS. This enhancement is attributed to the increased availability of active sites and the improved interaction between oxygen molecules and the OMS surface. The NaBH4 surface etching treatment provides a simple and scalable approach to unlock the full potential of OMS materials for ORR catalysis, paving the way for advancements in energy storage and conversion technologies.