A graphitic carbon nitride-coated quartz crystal microbalance gas sensor for H2 detection

Abstract

The demand for H₂ gas sensors is expected to grow in the near future owing to the increasing use of hydrogen fuel as a clean energy source. Conventional H₂ gas sensors tend to be based on composite materials containing noble metals, such as Pt, Pd, and Au, and many of these sensors require high operating temperatures. Therefore, the development of H₂ gas sensors that do not require the use of such noble metals and that can operate without heating to high temperature is desirable from the viewpoint of energy conservation and resources. Here, graphitic carbon nitride (g-C₃N₄), which possesses a two-dimensional structure and is composed of both carbon and nitrogen atoms, is used to prepare a sensor for H₂ gas. More specifically, a g-C₃N₄ film is formed on a quartz crystal microbalance (QCM) electrode to detect H₂ gas. This sensor acts based on a change in the resonant frequency of the QCM electrode in the presence of H₂ gas, and this change increases linearly with an increasing H₂ gas concentration. These results indicate that the g-C₃N₄-modified QCM electrode functions as a H₂ gas sensor. The mechanism responsible for H₂ sensing is the combination of H₂ with the nitrogen atoms from g-C₃N₄ to produce and release NH₃. The proposed sensor is limited to several hundred measurements due to the stability of g-C₃N₄, but the application of this g-C₃N₄ film to the QCM technique enables the detection of H₂ gas without requiring noble metals or heating for operation.