Water oxidation reaction could play a key role in sustainable energy conversion and storage processes. However, act as the major bottleneck in the energy conversion and fuel forming reactions due to the sluggish reaction kinetics and large overpotential. But, nature employed very efficient catalysts (low over potential (~160mV); high turnover frequency (~ 25,000 mmolO2 mol-1MnS-1) for this chemistry by utilising Mn4CaO5 cluster in photosystem II called water oxidation complex (WOC). Interestingly, nature utilised highly distorted cubane cluster and spin-state tuning and high-valent intermediate species to carry out the sequential proton and electron transfer reactions. Inspired by WOC, various forms of manganese phosphates and oxides were used to study the structure-function correlations of WOC. We have employed various manganese phosphate based materials as efficient water oxidation catalysts and demonstrated the role of Mn valency and asymmetric geometry induced by Jahn-Teller distorted Mn(III) ions. Later, we verified that the newly developed sub- 10 nm sized manganese oxides nanoparticles as the promising candidates and studied the role of size and asymmetric distortion at the atomic level. Interestingly, we have also confirmed the involvement of high-valent Mn=O intermediates during the water oxidation reactions. In this presentation, I will discuss the role of Mn valency, structural distortion and spin-state tuning at the atomic level towards improving the catalytic activity of the MnO nanoparticle. We anticipate that, our MnO platform could be further utilised to understand the structure-function correlations of WOC to achieve industrial level heterogeneous catalysts for water oxidation reaction.

Structural distortion and spin-state control of bioinspired Mn-based water oxidation electrocatalysts

ACS Spring Meeting 2021

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