Exploiting Free-Standing p-CuO/n-TiO2 Nanochannels as a Flexible Gas Sensor with High Sensitivity for H2S at Room Temperature

Hydrogen sulfide (H2S) is an extremely hazardous gas and is harmful to human health and the environment. Here, we developed a flexible H2S gas-sensing device operated at room temperature (25 °C) based on CuO nanoparticles coated with free-standing TiO2-nanochannel membranes that were prepared by simple electrochemical anodization. Benefiting from the modulated conductivity of the CuO/TiO2 p-n heterojunction and a unique nanochannel architecture, the traditional thermal energy was innovatively replaced with UV irradiation (λ = 365 nm) to provide the required energy for triggering the sensing reactions of H2S. Importantly, upon exposure to H2S, the p-n heterojunction is destroyed and the newly formed ohmic contact forms an antiblocking layer at the interface of CuS and TiO2, thus making the sensing device active at room temperature. The resulting CuO/TiO2 membrane exhibited a notable detection sensitivity for H2S featuring a minimum detection limit of 3.0 ppm, a response value of 46.81% against 100 ppm H2S gas, and a rapid response and recovery time. This sensing membrane also demonstrated excellent durability, long-term stability, and wide-range response to a concentration of up to 400 ppm in the presence of 40% humidity as well as outstanding flexibility and negligible change in electrical measurements under various mechanical stability tests. This study not only provides a new strategy to design a gas sensor but also paves a universal platform for sensitive gas sensing.