Ligand mediated self-assembly of cobalt nanoclusters for tunable supercapacitors

Abstract

Self-assembly of thiolated cobalt-based nanoclusters was achieved by a simple and one-step synthesis process towards the development of a tunable hybrid supercapacitor. Here, we report the wet chemical synthesis of self-assembly of cobalt nanoclusters (CoNCs) using three different thiols namely glutathione (GS), 3-mercapto propyl sulfonate (MPS) and 3-mercapto propionic acid (MPA) protected individually. The variation in the capping ability of the thiolate ligands brings the proximal changes in the optical, structural and electrochemical properties. In CoNCs, the structural and morphological changes that evolved from the obtained GS-CoNCs, MPS-CoNCs, and MPA-CoNCs were confirmed using UV–vis spectroscopy, XRD, and TEM analysis. The stability of CoNCs and binding states of cobalt metal were determined using TG and XPS analysis respectively. The divergence in the rigidifying nature of various thiolated cobalt nanoclusters significantly influences their capacitance ability for energy storage via altering the porosity and electron transfer characteristics. The rigid dense multifunctional ligands like GS facilitate the electron-hole hopping process in the nano-pockets available in GS, which enhances the energy storage capability and diffusion among ligand-metal-ligand chains. Wherein, the other two ligands MPS and MPA show comparatively lower supercapacitance activities due to diverse functionality and rigidify. The charge-discharge studies explore the supercapacitor behaviour of GS, MPS and MPA-protected CoNCs with the specific capacitance of 540, 494 and 358 F g−1 respectively at the current density of 1 A g−1.