Engineering Co 3 O 4 electrodes for efficient water oxidation Suresh Chandra Baral 1,2 , Somaditya Sen 1 , and Sudhagar Pitchaimuthu 2 * 1 Department of Physics, Indian Institute of Technology Indore, Indore, 453552, India, 2 Research Centre for Carbon Solutions, Institute of Mechanical, Processing and Energy Engineering, School of Engineering and Physical Sciences, Heriot-Watt University, United Kingdom Efficient anodic oxygen evolution reaction (OER) catalysts are critical for electrochemical H2production. While water oxidation catalyzed by earth-abundant materials is pivotal for the global-scale production of non-fossil fuels, most of the catalysts still require a high overpotential to reach the standard 10 mA/cm 2 due to the sluggish four-electron transfer. It has been well identified that at electrode potentials facilitating oxygen evolution, a sub- nanometer shell of the Co 3 O 4 is transformed into a more catalytically active X-ray amorphous CoO x (OH) y , which comprises di-µ-oxo bridged Co 3+/4+ ions. Additionally, defects can lead to apparent electronic delocalization, which enhances the carrier transport to participate in water-splitting reactions along the defective conducting channels and the water adsorption/activation on the catalyst surface. It has also been reported that strain in the lattice in Co-based oxides can convert low-spin Co³ + to a high-spin state Co³ + octahedra, which elongate along the z-axis to favor the water adsorption/activation on the catalyst surface. It favors faster electron transfer between apex-to- apex e* g orbitals [1] . Here, we have reported a specific engineering strategy to modulate the electronic structure, specific surface area, and the formation of defects for efficient water oxidation of the low-cost Co 3 O 4 electrodes. References 1. Zhang, X., Zhong, H., Zhang, Q.,et al.High-spin Co 3+ in cobalt oxyhydroxide for efficient water oxidation. Nat Commun 15 , 1383 (2024). https://doi.org/10.1038/s41467-024-45702-4.
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