Mixed-valent copper chalcogenides fabricated through the underpotential electrochemical oxidation of copper substrate

Electrochemical oxidation of copper substrate in a S²⁻ containing alkaline solution was investigated in this research, establishing a green procedure for the controllable synthesis of copper chalcogenides. Scanning electron microscopy (SEM) measurements showed that both the size and shape of the thus-synthesized Cu_xS particles could be manifested by conveniently adjusting the applied potential window or the scan rate of the cyclic voltammetry. Experiments showed that sulfide ions in the electrolyte facilitated the copper oxidation, resulting in the underpotential oxidation of copper and the subsequent in situ formation of Cu_xS nanoparticles. The successful synthesis of Cu_xS was confirmed by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Electrochemical properties of the as-obtained Cu_xS were characterized through the oxidation of glucose in an alkaline solution, where a well-isolated anodic peak could be observed in the cyclic voltammogram. The oxidation peak was found to have a linear relationship with the glucose concentration ranging from 0.5 mM to 3.0 mM with a sensitivity of 0.076 mA/mM. The calculated detection limit for glucose was about 9.46 μM. This in situ fabrication method is robust, producing Cu_xS-coated electrodes that yield consistent and highly reproducible results for the glucose oxidation. Graphical abstract: [Figure not available: see fulltext.].