Thermodynamic Stability and Intrinsic Activity of La1−xSrxMnO3 (LSM) as an Efficient Bifunctional OER/ORR Electrocatalysts: A Theoretical Study

William Hale,Pabitra Choudhury

doi:10.3390/catal12030260

William Hale, Pabitra Choudhury

Open Access

https://doi.org/10.3390/catal12030260

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Abstract

Perovskite oxides, being transition metal oxides, show promise as bifunctional catalysts being able to catalyze both oxygen evolution reactions (OER) and oxygen reduction reactions (ORR). These two reactions play a crucial role in energy storage and energy conversion devices. An important feature of perovskite catalyst is their ability to be tuned, as tuning can positively affect both reactivity and stability. In this study, Density Functional Theory (DFT) has been utilized to calculate both the equilibrium phase stability and the overpotentials (reactivity performance indicator of the catalysts) of La1−xSrxMnO3 (LSM) structures with different stoichiometry by introducing Mn and O vacancies for both the OER/ORR reactions. The electronic structures reveal that combined Mn and O vacancies can lead to higher catalytic activity for both OER and ORR due to the optimum filling of antibonding orbital electrons. Moreover, both O p-band centers and equilibrium phase stability plots show that LSM structures can be stable at normal OER/ORR operating conditions in an alkali medium.

Highlights

The pursuit of alternative energy sources for a more sustainable future has placed increased importance on the prospect of fuel cells, water splitting, and metal–air batteries [1,2]
We have calculated the overpotentials for different defect tunings of LSM for the bifunctional (OER/oxygen reduction reactions (ORR)) catalytic activity
The results of the tunings on the various calculated overpotentials clearly indicate that simultaneous B-site (Mn) and O vacancies, i.e., ALSMO, is the best-performing catalyst among all the LSM systems

Summary

Introduction

The pursuit of alternative energy sources for a more sustainable future has placed increased importance on the prospect of fuel cells, water splitting, and metal–air batteries [1,2]. OER and ORR are both critical to these technologies. To simplify the implementation of these technologies, a single efficient bifunctional catalyst capable of doing both OER and ORR is sought. Typical states of the art OER and ORR catalyst are noble metal catalyst that show limited bifunctional capability [1,2,3]. IrO2 or RuO2 are commonly used for OER, and Pt or Pd are commonly used for ORR [1,2]. Compounding on top of the insufficient bifunctional capability of these state-of-the-art catalysts is that the sacristy of the constituent noble metals would likely impede their widespread adoption

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