3-D Nanostructure Palladium Synthesis By Electrochemical Deposition for Hydrogen Sensor with Switching Resistance Characteristic in Normal Temperature and Pressure

Abstract

In the hydrogen industry, it is crucial to detect hydrogen leaks and monitor its concentration due to its highly explosive, flammable, and diffusive properties in the concentration range of 4%-75%. Until now, hydrogen sensors have been focused on oxide materials at high temperature and pressure conditions such as semiconductor and steel processes. However, in the future of the hydrogen industry, it is important to sense hydrogen at normal temperature and pressure (NTP). To develop hydrogen sensors with fast response time and high sensitivity specifically designed for NTP conditions, various material properties and structural aspects such as film, nanostructure, and multilayer are being experimentally explored.Metal resistance hydrogen sensors utilize changes in resistance due to hydrogen adsorption and absorption. Compared to other sensors such as catalytic and thermal conductivity sensors, metal resistance hydrogen sensors have advantages such as excellent sensitivity, response time, and selectivity. Palladium metal exhibits superior characteristics with regard to hydrogen compared to other metals, due to its low activation energy for hydrogen molecule dissociation reaction and high reactivity in absorbing hydrogen at NTP.[1] Also, palladium with 3-D nanostructures exhibits a switching resistance characteristic, where the resistance initially decreases rapidly and then increases because of hydrogen and palladium reaction.[2] This depends on the hydrogen concentration and exposure time, which is due to a phenomenon where the combined effects of characteristics such as hydrogen interstitial, phase transition, and volume expansion lead to different responses of hydrogen and palladium.In this study, we focused on the resistance switching characteristic of palladium, specifically its response to changes in hydrogen concentration and exposure time. We used this characteristic to experiment with both the material and structural properties of palladium nanostructures. We varied impurities and additives in the palladium electrodeposition solution to control the material properties, and varied parameters such as concentration, pH, and voltage using electrochemical methods for structural properties. Structural and material properties were analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). Sensing characteristics were then analyzed using a hand-made sensor platform with a Source Meter.[Reference][1] Dekura, S., Kobayashi, H., Kusada, K., & Kitagawa, H. (2019). Hydrogen in Palladium and Storage Properties of Related Nanomaterials: Size, Shape, Alloying, and Metal‐Organic Framework Coating Effects. ChemPhysChem, 20(10), 1158-1176.[2] Cho, S. Y., Ahn, H., Park, K., Choi, J., Kang, H., & Jung, H. T. (2018). Ultrasmall grained Pd nanopattern H2 sensor. ACS sensors, 3(9), 1876-1883.