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

The demand for H-2 gas sensors is expected to grow in the near future owing to the increasing use of hydrogen fuel as a clean energy source. Conventional H-2 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 H-2 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 H-2 gas. More specifically, a g-C3N4 film is formed on a quartz crystal microbalance (QCM) electrode to detect H-2 gas. This sensor acts based on a change in the resonant frequency of the QCM electrode in the presence of H-2 gas, and this change increases linearly with an increasing H-2 gas concentration. These results indicate that the g-C3N4-modified QCM electrode functions as a H-2 gas sensor. The mechanism responsible for H-2 sensing is the combination of H-2 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 H-2 gas without requiring noble metals or heating for operation.