Nanostructured platinum and platinum alloy based resistive hydrogen sensors: a review

As a future energy source hydrogen is used in many industrial applications such as chemical, semiconductor, transportation, etc. Hydrogen gas, which has many unusual properties compared to other gases, has the risk of being flammable and explosive when it is present in the atmosphere at concentrations of 4% and higher. We need hydrogen sensors both to determine the risks in advance and because we do not want the hydrogen gas, which is the source of energy, to be lost due to leakage. Hydrogen sensors are used in hydrogen production plants to determine hydrogen purity, for leakage and safety in all areas where hydrogen gas is used, and also in the medical application as hydrogen gas is a marker in disease diagnosis. Considering the classification of hydrogen sensors according to the physico-chemical sensing mechanism, the performance of resistive metallic hydrogen sensors is one of the two best [1]. In metallic resistive hydrogen sensors, Pd, Pt and their alloys are generally used as sensing materials [2,3]. In this study, the nanostructured platinum (Pt) and Pt alloy based resistive hydrogen sensor are reviewed and discussed in detail. Hydrogen sensing properties of Pt, Pt alloys, Pt layered structures in many nanostructures such as nanowires, nanoporous, thin films have been investigated [4-10]. The sensing mechanism of Pt-based resistive hydrogen sensors has been explained with scattering of charge carriers at surface, from defects, from grain boundary and formation of hydride (PtH_x) phenomenas depending on the increase or decrease of resistance in hydrogen environment.