Cu/Cu₂O/CuO catalyst generated by disproportionation for electrochemical dopamine sensing with improved stability and sensitivity

Electrochemical sensing has been widely used for monitoring the signals of biochemical molecules closely related to human health while there are strict requirements for the stability of electrode materials in detection. Cu₂O, as one of the ideal transition-metal oxides with low cost and exceptional physicochemical properties, has attracted much attention because of its satisfactory electrochemical activity, proper redox potentials and so on. However, the unsatisfactory conductivity and the limited stability of Cu₂O in aqueous solutions impact greatly on its application in electrochemical sensing. Herein, we prepared a monolithic Cu/Cu₂O/CuO film via electrochemical deposition followed by a mild disproportionation reaction. A Cu₂O/CuO layer is firstly formed after the electrodeposition process, then the disproportionation reaction of Cu₂O/CuO layer is induced by acidulated NaF solution, which not only leads to the increase of the content of protective CuO and the introduction of micronano metallic Cu with good conductivity, but also results in the moderate exposure of Cu₂O (1 1 1) with higher stability and acceptable catalytic activity. Through microstructure engineering, specific facet exposure and the chemical composition regulation, we obtained a Cu/Cu₂O/CuO film with higher surface area and enhanced conductivity, achieving enhanced sensitivity (880 μA mM⁻¹ cm⁻²), fast response (<0.4 s), low detection limit (96 nM) and superior stability, which is greatly beneficial for acquiring better catalytic activity and stable sensing performance towards dopamine (DA). This work provides a facile and low-cost way for the design of stable electrocatalysts based on Cu₂O in a perspective of facet exposure and phase transformation.