Effects of paramagnetic fluctuations on the thermochemistry of MnO (100) surfaces in the oxygen evolution reaction

TL;DR

This study explores how paramagnetic fluctuations influence the thermochemistry of MnO(100) surfaces during oxygen evolution reactions, revealing enhanced charge transfer and bond strengthening without changing reaction pathways.

Contribution

It introduces the NCMSM+U method to analyze the impact of paramagnetic fluctuations on surface thermochemistry, highlighting their role in reaction energetics.

Findings

PM fluctuations increase charge transfer to intermediates

PM state strengthens chemical bonds on the surface

Reaction pathways remain unchanged despite energy barrier variations

Abstract

We investigated the effects of paramagnetic (PM) fluctuations on the thermochemistry of the MnO(100) surface in the oxygen evolution reaction (OER) using the "noncollinear magnetic sampling method \textit{plus} $U$" (NCMSM$+U$). Various physical properties, such as the electronic structure, free energy, and charge occupation, of the MnO (100) surface in the PM state with several OER intermediates, were reckoned and compared to those in the antiferromagnetic (AFM) state. We found that PM fluctuation enhances charge transfer from a surface Mn ion to each of the intermediates and strengthens the chemical bond between them, while not altering the overall features, such as the rate determining step and resting state, in reaction pathways. The enhanced charge transfer can be attributed to the delocalized nature of valence bands observed in the PM surface. In addition, it was observed that chemical-bond enhancement depends on the intermediates, resulting in significant deviations in reaction energy barriers. Our study suggests that PM fluctuations play a significant role in the thermochemistry of chemical reactions occurring on correlated oxide surfaces.