Designable synthesis of reactive deep eutectic solvents (RDESs) in regulating Ni-based materials for an efficient oxygen evolution reaction

Abstract

Deep eutectic solvents (DESs) are burgeoning green solvents in materials chemistry; however, a lack of multifunctionality is a typical limitation for most reported DESs. Herein, we describe 8 task-specific reactive DESs (RDESs) composed of amino acids and nickel chloride hexahydrate (NiCl₂·6H₂O) that support the desired reactive function for fabricating Ni-based materials, preserving the cost-effectiveness and energy-efficiency properties of the one-step annealing process. The structure of amino acids in the hydrogen bonded network was studied by Fourier transform infrared spectroscopy (FT-IR). Then, the effects of chain length, functional group substitution and molar ratios on the thermodynamic stability of DESs were also explored. Finally, taking serine–NiCl₂·6H₂O and threonine–NiCl₂·6H₂O systems as examples, which were equipped with or without a methyl group, Ni and Ni@Ni(OH)₂ samples were prepared by a one-step annealing process, respectively. Notably, the obtained Ni@Ni(OH)₂ materials exhibited considerable oxygen evolution reaction (OER) performance in an alkaline environment. Therefore, our proposed RDESs with versatile types and functionalities will open new avenues for potential development in energy and environmental applications.