Sulphur-induced electrochemical synthesis of manganese nanoflakes from choline chloride/ethylene glycol-based deep eutectic solvent

Abstract

Deep eutectic solvents with the advantages of being less expensive, non-toxic, renewable, and biodegradable are emerging as versatile solvent systems for the electrochemical synthesis of advanced functional materials. Herein, we study the electrochemical deposition of Mn nanoflake arrays grown on Cu foam and the morphology evolution of Mn crystals in the early stages of nucleation and growth in a choline chloride/ethylene glycol-based deep eutectic solvent (Ethaline-based DES). Thiourea (TU) is an efficient additive that is found to promote the electrochemical reduction of Mn(II) species in Ethaline-based DES and induce the formation of Mn nanoflake architectures with a nanoporous configuration. Investigation of the nucleation and growth processes with chronoamperometric transients reveals that the presence of TU can accelerate the generation of homogeneous Mn nuclei and dramatically enhanced the nucleation rate by modifying the corresponding nucleation and growth model from 3D progressive to 3D instantaneous. TU is found to play an important role in the crystallization kinetics of Mn crystals and manipulate the shapes, sizes, and growth morphologies of the formed Mn films. Our work highlights the importance of additives for controlling the microtopography of nanostructured Mn in Ethaline-based DES for potential electrochemical applications.