Shape-controlled electrochemical synthesis of Au nanocrystals in reline: control conditions and electrocatalytic oxidation of ethylene glycol

Abstract

Gold nanocrystals (NCs) as advanced catalysts towards ethylene glycol (EG) electrooxidation in direct alcohol fuel cells (DAFCs) have some advantages, such as good poisoning-resistance and high electrocatalytic activity. The shape and size control of Au NCs are crucial to their electrocatalytic activity. In this work, the control of morphologies and sizes of prepared Au NCs in reline are systematically investigated by changing electrodeposition conditions: the applied potential, electrodeposition temperature, HAuCl₄ concentration and electrodeposition time. Results show that reline (a deep eutectic solvent (DES), a mixture of choline chloride and urea at the molar ratio of 1 : 2) plays an important part in the nucleation and growth of the star-like Au NCs. This approach for preparing star-like Au NCs in reline does not need any supporting electrolyte and organic solvent, and thus is more environmentally friendly than water as a medium. The electrode modified by the as-prepared Au nanostars (NSs) exhibits a good poisoning-resistance ability and electrocatalytic activity for EG electrooxidation in alkaline media. This strategy is a significant way for shape-controlled synthesis of noble metal nanomaterials in DESs that may have potential applications in fields of electrochemical sensors, electrocatalysis and fuel cells.