Transition Metal Schiff Base Complexes as Potential Non-Platinum Catalysts for Hydrogen Evolution Reaction: A Comparative Study of Co (II) and Ni (II)

The necessity for non-platinum catalysts in the context of hydrogen evolution is predominantly driven by the limited availability and substantial cost of platinum, which is currently the most effective catalyst for this reaction. In this study, we present the findings of the first principle calculation of alternative transition metals with the potential to compete with platinum for catalytic HER. To this end, we employed Chemdraw, Material Studio DMOL3, MATLAB, and other relevant software for the modeling and structural analysis, electronic properties, Gibbs free energy calculation, and calculation of overpotential, respectively for Co (II) and Ni (II) (E)-3-hydroxy-N’-(1-(6-methyl-2,4-dioxo-3,4-dihydro-2H-pyran-3-yl)ethylidene)-2-naphthohydrazide complexes. The investigation revealed that the Co (II) and Ni (II) complexes are ion exchange resin catalyst that exhibited a coordination number of 6, with the former displaying a tetradentate coordination and the latter exhibiting a bidentate coordination. The atomic charges indicated that the nickel (II) complex possesses seven electropositive centers, while the cobalt (II) complex has eight. The predicted carbon centers, C8, C11, C12, C15, C18, C19, C20, and C22, were identified. According to the surface energy values, Ni (II) Schiff base complexes exhibit superior efficiency for HER, attributable to their enhanced surface stability and reactivity. These properties render Ni (II) complexes more suitable for catalytic applications, whereas Co (II) complexes may necessitate further optimization to achieve comparable performance. The free energy values of the Co (II) (0.126977 eV) and Ni (II) (-0.12503 eV) Schiff base complexes indicate significant differences in their catalytic efficiency for HER. The negative free energy of the Ni (II) complex indicates that the reaction is exothermic, meaning it releases energy and proceeds spontaneously. The overpotential of Co (II) is found to be remarkably low (1.054257189511323e-25 eV), suggesting its potential to function as an ideal catalyst for the Hydrogen Evolution Reaction (HER). The negligible overpotential of cobalt renders it a promising candidate as a theoretically ideal HER catalyst due to its capacity to form stable Schiff base tetradentate ligands, thereby enhancing its electrochemical properties. Nickel, which exhibits a relatively high overpotential, remains a viable and cost-effective option for practical applications. However, further investigation is necessary to validate the performance of cobalt, which exhibits an extraordinarily low overpotential, for HER applications.