Raman Spectroscopic\nObservation of Electrolyte-Dependent\nOxygen Evolution Reaction Intermediates in Nickel-Based Electrodes

Oxygen evolution reaction (OER) is the counterpart in\nhydrogen\nproduction by water electrolysis. Further challenges have been required\nto bypass the energy consumption processes in the OER. It is still\nimportant to unveil the OER intermediates toward effective green hydrogen\nproduction. In this study, we conducted in situ Raman observation\nof the OER intermediates over Ni nanohole-array electrodes in the\nvarious electrolyte conditions. Ni nanohole-array electrodes were\nprepared with interference exposure methods. Intense Raman peaks were\nobserved from Ni–OH, Ni-OOH, and active oxygen species as the\nOER intermediates. The OER behavior can be classified with the reactants,\nsuch as OH<sup>–</sup> and H<sub>2</sub>O. The presented study\ndemonstrates the importance of the electrolyte for the designing active\nOER catalysis for the next generation energy society.