Theoretical exploration electrocatalytic active of spinel M2CoO4 (M = Co, Fe and Ni) as efficient catalyst for water splitting

Spinel oxides have shown promising electrocatalytic properties for water splitting. Here, density functional theory was carried out with (DFT + U) to study the reaction mechanism of water splitting on the (110) surface of the spinel oxides. The mechanism process and catalytic activity of M2CoO4 (M = Co, Fe and Ni) are not yet understand in depth. In this case, a systematic study of water splitting on different activation sites of our supported systems are presented. The optimum active site of optimized structures were used to explore the free energy profile during the entire reaction of water oxidation, indicating that the rate-determining step of the oxygen evolution reaction (OER) is the third step to form atomic oxygen species. The Fe2CoO4 and Co3O4 surfaces were more catalytically efficient than the Co2NiO4 surface with small overpotentials of 0.33 and 0.35 V, respectively. Analysis of the electronic structure shows that the main density of states was contributed by 3d states of metal near the Fermi energy, they are all exhibition metallic. On preferred site were investigated, The formation energies, limiting potential, overpotential and activation energy of the OER intermediate species (OH, O, and OOH) are studied. Furthermore, the thermodynamic properties in each elementary reaction step are evaluated, with the results implying that both of the M2CoO4 surfaces share the same mechanism path (H2O -> OH -> O -> OOH -> O-2). It is found that the formation of atomic O requires an activation energy of 0.56 eV on the Co3O4(111) surface and 0.38 eV on the Fe2CoO4(111) surface, indicating that the Fe2CoO4 surface has significantly better catalytic properties than the other surfaces. Our results suggest that the these spinel oxide compounds are suitable for catalysis of water splitting.

Automated summary

The study used density functional theory to investigate the water splitting reaction mechanism on the (110) surface of spinel oxides, finding that the Fe2CoO4 surface has significantly better catalytic properties than others.