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.