Effect of Cyclic Voltammetry Activation in Hydrochloric Acid on the Oxygen Reduction Performance of Screen-Printed Gold Electrodes

Herein, screen-printed gold electrodes (SPGEs) were electrochemically activated via cyclic voltammetry in 0.5 M HCl, with the selection of HCl guided by preliminary comparisons of activation behaviour in different acidic media. Optimal surface activation was achieved after 12 cycles. Structural and morphological characterization by SEM-EDX and XRD revealed the development of a rougher, more porous surface and the formation of catalytically active gold oxide species. Electrochemical evaluation demonstrated a substantial enhancement in oxygen reduction reaction (ORR) performance, including a 120 mV positive shift in onset potential and a 27% increase in current density under similar experimental conditions compared to the unmodified electrode. The double-layer capacitance (Cdl) increased from 1.23 µF to 2.00 µF, indicating enhanced capacitive behaviour. Electrochemical impedance spectroscopy (EIS) further revealed a dramatic reduction in total charge transfer resistance (Rct), decreasing from 79.14 Ω to 9.4 Ω, signifying improved interfacial electron transfer kinetics. These enhancements are attributed to a combination of factors, including removal of surface contaminants, chloride induced restructuring, increased conductivity, and greater exposure of catalytically active gold oxide sites. These performance improvements are particularly relevant for sensing applications, where SPGEs are widely used as practical and low-cost platforms for dissolved oxygen detection. This study highlights cyclic voltammetry in 0.5 M HCl as a simple and effective approach for improving the electrocatalytic performance of SPGEs in ORR and related sensing applications.