Controlled oxidation of Cu particles by H₂O₂ to form Cu/CuO nanostructure with enhanced gas sensing performance

Gas sensors based on metal/metal oxide heterostructures have shown rapid advancements due to their excellent sensing performance. However, it is difficult to control the formation of Cu/CuO nanostructure due to the easy oxidation of copper and limits its sensing application. Herein, we reported the controlled oxidation of Cu superfine particles (SPs) to form Cu/CuO nanostructure via reducing CuO with monoethanolamine, oxidized with H₂O₂ and then in-situ annealed at 250 °C. The organic residue generated during the reducing step plays a key role in controlling the oxidation of Cu SPs to form Cu/CuO nanostructure. The nanomaterial was used to fabricate gas sensor, which presents excellent p-type sensing performance to ethanol with good selectivity and a good linear relationship in the range of 1 to 100 ppm ethanol. The response to 100 ppm ethanol can be up to 99.40 under 200 °C operating temperature, and the response under 250 °C is 30.66 with the shorter response and recovery time of 214 s and 74 s, respectively. The sensing mechanism can be explained by the adsorption–desorption model. This study provides a promising strategy for the synthesis of Cu/CuO nanostructure and open a new avenue for the development of highly sensitive ethanol sensor.