Ag₂O Loading-Dependent Interfacial Properties of Ag₂O/Co₃O₄ Composites for Gas-Phase and Electrochemical Sensing

Ag₂O-loaded Co₃O₄ composites (Ag₂O/Co₃O₄) were prepared by the sol-gel auto-combustion method. Their morphology, microstructure, and textural properties were characterized by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. The composites were evaluated as conductometric sensors for hydrogen (H₂). The Ag₂O/Co₃O₄-0.5 sensor showed an enhanced response to H₂ over the investigated concentration range of 2000-10,000 ppm at an optimal operating temperature of 125 °C compared with pure Co₃O₄. The electrocatalytic activity of the composites was also investigated after spray-coating them onto screen-printed carbon electrodes (SPCEs). Cyclic voltammetry (CV) showed an enhanced response to uric acid for the Ag₂O/Co₃O₄-1.0/SPCE compared with Co₃O₄/SPCE, with a sensitivity of 2.6 μA μM^-1 cm^-2, satisfactory reproducibility and stability, and a limit of detection (LoD) of 147 nM. These findings suggest that Ag₂O/Co₃O₄ composites are promising materials for both gas and electrochemical sensing.