Facile Dual-Ligand Modulation Tactic toward Nickel–Cobalt Sulfides/Phosphides/Selenides as Supercapacitor Electrodes with Long-Term Durability and Electrochemical Activity

The use of high electrochemical active binary nickel–cobalt sulfides/phosphides/selenides (Ni–Co–X, X = S, P, Se) as electrochemical energy storage materials still has a space for improvement because they become electrochemically unstable during long-term use. Herein, a facile and cost-effective dual-ligand synergistic modulation tactic is described to substantially improve the durability of Ni–Co–X (X = S, P, Se) at the atomic level by partially substituting S, P, and Se ligands into the nickel–cobalt hydroxide precursor, respectively. Remarkably, the dual-ligand electrodes on Ni-foam achieve superior durability and high electrochemical activity when used as positive electrodes in supercapacitors. Impressively, the density functional theory calculations demonstrate that the OH ligand in NiCo2(MOH)x (M = S, P, Se) could attract electrons from metal–S/metal–P/metal–Se bonds to the metal–O bond, enhancing the binding energy of metal–S/metal–P/metal–Se bonds and improving the long-term durability of Ni–Co–X (X = S, P, Se) in alkaline electrolytes. Moreover, OH and S/P/Se ligands could effectively alter the electron structure and result in favorable electrochemical activity. Overall, this tactic could offer an exciting avenue to achieve long-term durability and electrochemical activity of supercapacitor electrodes simultaneously.