Unveiling the redox mechanism of cerium doped in nickel for alkaline hydrogen evolution: a theoretical exploration

Abstract

Electrochemical water electrolysis under alkaline conditions holds immense potential in clean energy production and storage. Density functional theory (DFT) computations were employed to investigate the in situ redox behavior of Ce doped in Ni under alkaline conditions. The Pourbaix diagrams for Ce atomic surface reactions at pH = 12 showed stability of H₆Ce@Ni below −0.48 V, persistence of Ce(OH)₅@Ni from −0.48 V to −0.34 V, and endurance of CeO₄@Ni beyond −0.34 V. On analyzing the Bader charges, the oxidation states of central Ce atoms were found to be +3, +4, and +4, respectively. In these stable phases, oxidized Ce and partially oxidized Ni around Ce cooperated in boosting the hydrogen evolution reaction. Additionally, the interaction between Ce's f-orbitals and H's s-orbitals assisted in reducing the energy barrier for water splitting. Ce(OH)₅@Ni emerged as the most plausible active phase following the Volmer–Heyrovsky mechanism, with a reaction energy barrier not larger than 0.43 eV. Thus, this investigation sheds light on the complex interplay between stable redox phases and catalytic processes, contributing to the development of efficient and sustainable hydrogen production.