Ce-doped self-assembled ultrathin CoOOH nanosheets as efficient oxygen evolution reaction electrocatalyst

Abstract

For transition metal oxyhydroxides, morphology modification and ion doping are widely used strategies for improving the performance of water catalytic oxidation. However, how to distinguish the contribution of different factors to the oxygen evolution reaction (OER) performance is still a serious challenge. In this study, Al ions can control the morphology of CoOOH in cycle of nanosphere-nanosheet-nanosphere, and Ce-doping can significantly improve the OER activity of CoOOH, with an overpotential of 263 mV@50 mA cm −2 and low Tafel slope of 53.74 mV dec −1 . In order to explain the above interesting experimental phenomena, detailed characterization has been carried out, such as high-resolution transmission electron microscopy (HRTEM) and electrochemical tests. At the same time, the mechanism of OER performance improvement was discussed based on electrochemical testing and density functional theory (DFT) calculations. Subsequently, the OER activities of different reactive sites, such as Al, Co, Ce, and oxygen vacancies (O v ), have been compared. As the main active center of OER, Ce ion has a minimum potential barrier of 1.71 eV. The results show that the adjustment of the adsorption intensity of the oxygen-containing species by Ce ions dominants the potential-determining step. Meanwhile, the synergistic effect of Ce and Co has also been confirmed based on the d-band theory. The CAC-12 electrocatalyst was prepared via a facile hydrothermal method at 120 °C. The electrocatalyst exhibited an outstanding OER performance with an overpotential of 263 mV at 50 mA cm −2 . The introduction and etching of Al can control the morphology of CoOOH in circle order of nanosphere-nanosheet-nanosphere. The catalytic ability of different active sites is in order of Ce>Co>O v >Al, and the analysis based on d-band theory proves that Co and Ce have a synergistic effect. • The chronoamperometry measurement was used to correct LSV curve. • The Al-controlled CAC-12 catalyst has the characteristics of self-assembled morphology. • The Ce-doped CAC-12 catalyst exhibites a high OER activity (263 mV@50 mA cm −2 and 370 mV@100 mA cm −2 ). • A rough catalytic ability order of different active sites in CoOOH is given: Ce>Co>O v >Al. • The synergistic effect between Ce and Co was found based on the d-band theory.