NiCo2O4 nanoparticles rich in oxygen vacancies: Salt-Assisted preparation and boosted water splitting

Xiaobo He; Yuanchu Dong; Fengxiang Yin; Guoru Li; Xinran Zhao

doi:10.3389/fchem.2022.996084

NiCo₂O₄ nanoparticles rich in oxygen vacancies: Salt-Assisted preparation and boosted water splitting

Front Chem. 2022 Sep 15:10:996084. doi: 10.3389/fchem.2022.996084. eCollection 2022.

Authors

Xiaobo He¹, Yuanchu Dong¹, Fengxiang Yin¹, Guoru Li¹, Xinran Zhao²

Affiliations

¹ Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou, China.
² College of Chemical Engineering, Beijing University of Chemical Technology, Beijing, China.

Abstract

NiCo₂O₄ is a promising catalyst toward water splitting to hydrogen. However, low conductivity and limited active sites on the surfaces hinder the practical applications of NiCo₂O₄ in water splitting. Herein, small sized NiCo₂O₄ nanoparticles rich in oxygen vacancies were prepared by a simple salt-assisted method. Under the assistance of KCl, the formed NiCo₂O₄ nanoparticles have abundant oxygen vacancies, which can increase surface active sites and improve charge transfer efficiency. In addition, KCl can effectively limit the growth of NiCo₂O₄, and thus reduces its size. In comparison with NiCo₂O₄ without the assistance of KCl, both the richer oxygen vacancies and the reduced nanoparticle sizes are favorable for the optimal NiCo₂O₄-2KCl to expose more active sites and increase electrochemical active surface area. As a result, it needs only the overpotentials of 129 and 304 mV to drive hydrogen and oxygen evolution at 10 mA cm^-2 in 1 M KOH, respectively. When NiCo₂O₄-2KCl is applied in a symmetrical water splitting cell, a voltage of ∼1.66 V is only required to achieve the current density of 10 mA cm^-2. This work shows that the salt-assisted method is an efficient method of developing highly active catalysts toward water splitting to hydrogen.

Keywords: hydrogen evolution reaction; oxygen evolution reaction; salt-assisted method; spinel; water splitting.