Title: Recent advances resistive metallic hydrogen sensors

Abstract

Hydrogen (H2), as a renewable energy source, has numerous applications such as chemical production, fuel cell technology, rocket engines, fuel for cars etc. The detection of H2 is so important in safety issue due to the flammable and explosive properties of H2 gas, in a H2 source for leak detection, in H2 production process because of real-time quantitative analysis of production and in determining the human digestive system diseases due to its biomarker properties. H2 sensors can be divided into seven categories depending on physicochemical detection mechanism and these are catalytic, electrochemical, resistor-based, work function-based, mechanical, optical, and acoustic. We focused on the metallic resistive type H2 sensor that is a part of a resistor-based H2 sensor and has many advantages sensor parameters. Palladium (Pd), platinum (Pt), and their alloy are used as sensitive materials for the metallic resistive type H2 sensor. Pd, Pt and their alloy in the nanostructure form of nanofilm, nanoporous and nanowire are fabricated by using sputtering, electrochemical deposition and thermal evaporation. The H2 sensing properties of nanostructured Pd, Pt and their alloy have been investigated depending on temperature and concentration. The sensing mechanism of the nanostructured Pd and Pt resistive H2 sensors will be discussed in details. In addition, the sensor parameters of the nanostructured Pd and Pt resistive H2 sensors will be compared. The sensor response of Pd and Pt thin film and the schematic illustration of electrical transport under different conditions at room temperature. Pt thin film shows higher sensitivity and a lower limit of detection than Pd film. However, the advantages of Pd thin film sensor are lower response time and unresponsive to the presence of oxygen compared to Pt thin film.