Sustainable energy is an important topic with increasing energy demands, worldwide. Hydrogen energy is one of the promising directions in developing new energy resources. One of the promising methods for hydrogen generation is oxygen evolution reaction (OER) process. However, because of the high energy barrier associated with oxygen evolution reaction, novel catalysts are desired to promote catalytic activity. Among others, transition metal oxides have been one of the optimal materials for oxygen evolution reaction. Recent experimental studies have evaluated the catalytic performance of cobalt oxide structures. However, the fundamental details into the mechanism of OER is largely unknown, this study is focused on providing such insights of OER using first-principle calculation with density functional theory. To overcome the underestimation of the band gap, Hubbard correction (Hubbard values U = 3.3 eV for Co, 3.7 eV for Cr) is applied to the PBE functional throughout the calculation. The Hubbard correction values are validated by comparing to the experimental band gap values and the lattice parameters.The electronic properties of pristine and Cr-substituted cobalt oxides structures were investigated by computing their band structures, density of states, and projected density of states. This study clearly reports a strong correlation between the band gap and the concentration of Cr substituted in the substrate framework. The computed band gap stays relatively constant and was consistent with the experimental values of Co3O4 for Cr concentration less than 1.25.
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