Theoretical Study on the Electrochemical Water Splitting of Two-Dimensional Metal–Organic Frameworks TM3C12O12 (TM = Mn, Fe, Co, Ni)

Abstract

Recently, two-dimensional metal–organic frameworks have received increasing interest due to their flexible components with adjustable structures, abundant accessible active sites, and high conductivity. In this paper, the thermal stability and electronic structure of 2D transition metal–organic framework (TM-O MOF, TM = Mn, Fe, Co, Ni) single-layer structures are systematically explored using first-principles calculations. Theoretical results reveal that these TM-O MOF systems exhibit good thermal stability due to sufficient π-electron conjugation and effective interaction between the transition metal and the organic ligands. They all show metallic behavior with spin magnetism. The catalytic property of TM-O MOFs depends on the d-electron occupations in the TM atoms. Interestingly, the active sites of HER and OER are O atoms and TM atoms, respectively, enhancing the water splitting process. The Co-O MOF shows a good HER and OER catalysis performance with the Gibbs free energy of adsorbed hydrogen atoms ΔG*H = 0.02 eV and the over potential ηOER = 0.53 V. The insights confirm the stability and highlight the outstanding water splitting catalytic performance of 2D MOFs under normal reaction conditions.