Reaction Pathways for Oxygen Evolution Promoted by Cobalt Catalyst

Abstract

The in-depth understanding of the molecular mechanisms regulating the water oxidation catalysis is of key relevance for the rationalization and the design of efficient oxygen evolution catalysts based on earth-abundant transition metals. Performing ab initio DFT+U molecular dynamics calculations of cluster models in explicit water solution, we provide insight into the pathways for oxygen evolution of a cobalt-based catalyst (CoCat). The fast motion of protons at the CoCat/ water interface and the occurrence of cubane-like Co-oxo units at the catalyst boundaries are the keys to unlock the fast formation of O-O bonds. Along the resulting pathways, we identified the formation of Co(IV)-oxyl species as the driving ingredient for the activation of the catalytic mechanism, followed by their geminal coupling with O atoms coordinated by the same Co. Concurrent nucleophilic attack of water molecules coming directly from the water solution is discouraged by high activation barriers. The achieved results suggest also interesting similarities between the CoCat and the Mn 4 Ca-oxo oxygen evolving complex of photosystem II.

Ultrasonication-assisted ultrafast preparation of multiwalled carbon nanotubes/Au/Co3O4 tubular hybrids as superior anode materials for oxygen evolution reaction

“…Fig. 8 showed a generalized version of the OER cycle, which has been derived from the work of Guidoni and co-workers for cobalt-catalyst and Nørskov and co-workers for RuO 2 [54,55]. A reaction circle contained four electron transfer steps.…”

Water Oxidation at Electrodes Modified with Earth‐Abundant Transition‐Metal Catalysts

“…[30][31][32] Several reviews have been published from different perspectives, [33][34][35][36] although the literature on the use of first row transition metal oxo/hydroxides for water oxidation is so vast that it is an impossible task to classify and put into context all the results. After decades of research, there are still many open controversies regarding function, stability and performance, with contradictory data available.…”

Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

“…Among OER catalysts, Co oxides (CoO x ) have been shown to possess desirable activity over a broad range of pH values (12,16,18), from near-neutral to alkaline conditions. Substantial work has been aimed at understanding relationships between structure, mechanism, and activity (19,20,21,22,23,24,25,26). This has led to novel insights into the nature of catalytically active sites at the atomic scale (19,25,27,28), as well as the role of structural transformations from the resting to the catalytic state (29,30,31,32).…”