Potential of P-Type Cooper Oxides, N-type Titanium Oxides and their Mixtures as Resistive Hydrogen Gas Sensors - A Review

Metal oxides (e.g. SnO2, ZnO, TiO2) have been widely investigated materials for gas sensing applications, including hydrogen detection. However, the potential for hydrogen sensing of metal oxides such as CuO, In2O3, NiO, exhibiting p-type conduction, has been largely overlooked. Over the last 15 years, structures based on TiO2 and CuO have gained increasing interest as a promising system for hydrogen detection. Therefore, this article aims to: 1) provide an overview of the performance of TiO2 as a reference material and discuss methods to enhance its sensing performance, 2) summarize and highlight the role of copper oxides in hydrogen gas detection, as the materials that have predominantly been studied for H2S detection, 3) review efforts made to improve the sensing performance of heterostructures of CuTiOx, from structures with charge compensation effect to those successfully sensing hydrogen, 4) present the potential of CuTiOx for H2 detection.