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

Abstract

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.