Response Of Hydrogen Sensor Research Articles

Membrane-electrode junction properties for optimum potentiometric hydrogen sensor response

Membrane-electrode junction properties for optimum potentiometric hydrogen sensor response

Quaternary conducting Cs/GO/PANi hydrogel composites: A smart material for room temperature hydrogen sensing

Hydrogen sensors are essential for hydrogen energy technology development and safety monitoring. However, hydrogen sensing is difficult because it requires effective and fast detection of tiny quantities of hydrogen. In situ oxidative radical polymerization is used in this study to combine polyaniline (PANi) with a chitosan/graphene oxide (Cs/GO) hydrogel, which is very good at conducting electricity, to make it sensor. FTIR, XRD, SEM, and UV were used to evaluate the material's functional groups, crystal structure, morphology, and bandgap. This work shows that Cs/GO/PANi can synthesise a hydrogel-based sensor. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometry (CA) were used to evaluate electron transfer mobility, redox behaviour, and hydrogen sensing. Using a hydrogen source with a concentration of 0.5–2.5 M KOH, the hydrogen sensor's response time, recovery sensitivity, and limit of detection were found to be 0.4 s, 0.8 s, 54.3748 μAM, and 3.5520 μM, respectively. Under conventional conditions, the experiment demonstrated significant sensing capabilities at ambient temperature. According to the research, the sensor works so well because of the π-π stacking interaction, the irregular structure, and the way the GO-based hydrogel and PANi work together.

Hydrogen response of palladium nanoparticles washed with different solvents

Hydrogen sensor response of palladium (Pd) nanoparticles changes when the nanoparticles are washed with different solvents prior to device formation. This study presents the effect of washing Pd nanoparticles with distilled water or ethanol on their hydrogen response. The change induced in the surface characteristics of the Pd nanoparticles after washing is analysed with the help of UV–Vis absorption spectroscopy and glancing angle X-ray diffraction (GAXRD) studies. The nature of strain in nanoparticles after washing is particularly analysed from GAXRD data to understand the hydrogen response mechanism. The performance of the nanoparticle-based devices in humid ambient was also studied and the results were correlated to the consequence of sample washing. A suitable sensing mechanism within the purview of Langmuir model is discussed to understand the role of washing of the palladium nanoparticle yield.

Effect of Capping-Agent Concentration on Size and Size Dispersity of Palladium Nanoparticles for Resistive-Type Hydrogen Sensors

The size attributes in palladium nanoparticle yield were found to influence the hydrogen sensor response in resistive devices, and the sensing mechanism was correlated with the variation of particle size from large to small in a particular synthesis product. The quantity of polyvinylpyrrolidone (PVP), the stabilizer used in this study, was varied during synthesis, and the resulting sizes were determined by high-resolution transmission electron microscopy (HRTEM). The size tuning by the capping agent PVP was also confirmed by UV–Vis spectroscopy via a detailed analysis of the experimental spectra, which revealed an interesting shift of the major absorption peaks with the increase in PVP. Glancing-angle x-ray diffraction (GAXRD) studies were undertaken to highlight the face-centred cubic crystallinity of the drop-cast nanofilms on thin glass substrates, as well as to evaluate the variation in crystallite cluster size by analyzing the major diffraction peaks. The size variation from HRTEM and GAXRD studies was found to match within the limits of experimental accuracy. The hydrogen sensor studies showed good room temperature response with typical size-dependent characteristics. The mechanistic control of the hydrogen activity over the mixed sized nano-films at room temperature (RT) and beyond RT is elaborately discussed.

Modeling of hydrogen atom diffusion and response behavior of hydrogen sensors in Pd-Y alloy nanofilm.

To detect hydrogen gas leakage rapidly, many types of hydrogen sensors containing palladium alloy film have been proposed and fabricated to date. However, the mechanisms and factors that determine the response rate of such hydrogen sensor have not been established theoretically. The manners in which response time is forecasted and sensitive film is designed are key issues in developing hydrogen sensors with nanometer film. In this paper, a unilateral diffusion model of hydrogen atoms in Pd alloy based on Fick’s second law is proposed to describe the Pd–H reaction process. Model simulation shows that the hydrogen sensor response time with Pd alloy film is dominated by two factors (film thickness and hydrogen diffusion coefficient). Finally, a series of response rate experiments with varying thicknesses of Pd–Y (yttrium) alloy film are implemented to verify model validity. Our proposed model can help researchers in the precise optimization of film thickness to realize a simultaneously speedy and sensitive hydrogen sensor. This study also aids in evaluating the influence of manufacturing errors on performances and comparing the performances of sensors with different thicknesses.

Surface topography and hydrogen sensor response of APCVD grown multilayer graphene thin films

Atmospheric pressure chemical vapour deposition was employed to deposit graphene thin films on thermally oxidized p-silicon substrates. Raman spectroscopy and energy dispersive spectroscopy revealed the multilayer nature and the composition of the grown graphene films respectively. The defective nature and the defect density of the graphene films were determined from the Raman experiments. Field effect scanning electron microscopy, transmission electron microscopy and atomic force microscopy were used to study the surface morphology of the multilayer graphene films. The film topography was sensitive to temperature and time of growth. A suitable growth mechanism has been proposed to explain the topographical observations. The large surface area of the multilayer films was found to be suitable for hydrogen sensor applications and the sensing results were correlated with the morphology of the grown films.

Effect of gamma irradiation on Schottky-contacted vertically aligned ZnO nanorod-based hydrogen sensor

We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor’s performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment.

Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

Experimental study on optical fiber bundle hydrogen sensor based on palladium-silver optical thin film

In this paper, a 20 nm palladium-silver (Pd/Ag) ultrathin optical film is used for hydrogen gas sensing. The mole ratio of the two metals is controlled at Pd:Ag=3:1. In the direct current (DC) sputtering machine, the optical thin film is evaporated on the optical glass. Compared with pure palladium, the Pd/Ag alloy can increase the life and the stability of the sensing film. Optimum sputtering parameters for Pd/Ag alloy are presented in this paper, and the effects of different experimental conditions for hydrogen sensor are investigated, including the temperature effect, humidity effect and cross sensitivity of hydrogen sensor for different gases. The experiment results indicate that the hydrogen sensor based on Pd/Ag optical thin film exhibits good sensing characteristics. The existing of CO and water in hydrogen increases the response time and decreases the response amplitude of optical fiber bundle hydrogen sensor. The experiment results show that the increasing temperature can eliminate the effect and shorten hydrogen sensor response time effectively.

Optical Path Analysis of the Optical Fiber Bundle Hydrogen Sensor

The present work investigates reflectivity and optimal reflective distance of optical fiber hydrogen sensor in over 0～4000um range. The approximate equality of reflective distance in two optical paths increases signal to noise ratio for optical hydrogen sensor, the fabrication of optical path could eliminate the internal noise and external interferences, and provides higher stability for hydrogen sensor. Through a series of simulation experiments it was found that different reflective distances determine the sensitivity and amplitude response of hydrogen sensor. When the reflective distance was about 1mm in optical path, the sensitivity of optical hydrogen sensor could reach the peak value.

A comparison of test methods for the measurement of hydrogen sensor response and recovery times

Response time is a critically important property of hydrogen safety sensors. Recovery times are less important from a safety perspective, but are often quoted as an indication of the speed of operation of a sensor. However, the measured values depend highly on the method used to evaluate them. The purpose of this work is to assess the suitability of different methods, both flow and diffusion-based, for the measurement of sensor response and recovery times. Four methods have been tested in terms of their repeatability and practicality of execution, as well as the accuracy of their results compared to the manufacturer’s specifications. It was found that each method has its own advantages and limitations, which are discussed herein. For the measurement of response times, a diffusion-based method was found to give the shortest and most precise values and is therefore recommended. However, the flow-based method was found to be the most convenient experimentally and is the only method that is suitable for the measurement of recovery times over a wide concentration range.

The Response of Hydrogen Sensor to Environment

In many hydrogen sensor applications, the ambient environment applies effects on sensor response. Some environmental parameters may cause significant function changes in sensor performance. These parameters include temperature, humidity, pressure and gas flow rate, among others. Calibration and compensation for these effects are thus needed to acquire meaningful and accurate results from sensor measurements. In this report, a custom-designed hydrogen sensor test station is described. The test station provides simultaneous and accurate control of gas composition, gas flow rate, temperature, humidity and pressure. The test procedures were designed to examine sensor response to the changes of these parameters. A number of hydrogen sensors of various types had been tested in a series of testing processes. The general behavior of these gas sensors was studied and gave a brief overview of hydrogen sensors in present market.