Effect of a Series Connection of a Bi-Electrolyte Hydrogen Sensor in a Leak Detector

( Hyeuk Jin Han ),( Chong Ook Park ),( Young Kyu Hong ),( Jong Suk Kim ),( Jeong Woo Yang ),( Yoon Seo Kim ) 한국센서학회 2015 센서학회지 Vol.24 No.1

Conventional leak detectors are widely based on helium gas sensors. However, the usage of hydrogen sensors in leak detectors has increased because of the high prices of helium leak detectors and the dearth in the supply of helium gas. In this study, a hydrogen leak detector was developed using solid-state hydrogen sensors. The hydrogen sensors are based on Park.Rapp probes with heterojunctions made by oxygen-ion conducting Yttria-stabilized zirconia and proton-conducting In-doped CaZrO3. The hydrogen sensors were used for determining the potential difference between air and air balanced 5 ppm of H2. Even though the Park.Rapp probe shows an excellent selectivity for hydrogen, the sensitivity of the sensor was low because of the low concentration of hydrogen, and the oxygen on the surface of the sensor. In order to increase the sensitivity of the sensor, the sensors were connected in series by Pt wires to increase the potential difference. The sensors were tested at temperatures ranging from 500.600oC.

Hydrogen Detecting Sensor Technology for Various Environments

Hyungtak Seo 한국물학회 2019 한국물학회지 Vol.7 No.1

Recently, hydrogen as a renewable energy carrier has attracted attentions for fuel cell vehicles, energy storage and generation, bio and health applications. However, there is a critical issue of hydrogen about safety because hydrogen is colorless, odorless and explosive in 4 % H2 in air. This characteristic has been considered as a bottle-neck to spread hydrogen-based applications.1 In addition, it is essential to monitor hydrogen concentration at high precision over wide range of concentration at ppm- 100%. Hence, the research on hydrogen detecting sensor to ensure hydrogen safety and wide-range concentration control has been actively conducted. In addition to the typical electrical sensing, recent research on hydrogen gas sensors has focused on optical sensor using IR detector but it is subject to critical issues of a high cost, lots of electrical connections2 and accidental errors. Now, visible coloration hydrogen sensor (chemochromic) has been reported with various materials3. This chemochromic sensor is electrical power-free and is available in flexible applications. In this presentation, I report various hydrogen sensing technique based on our group developed active materials such as (1) nanostructure oxides (WO3, MoO3) for reversible and sulfide (CuS) for irreversible for chemochromic sensing, (2) super lattice structure based on Pd alloy for wide range hydrogen dissociation from 100 ppm to 100 %. Chemochromic hydrogen sensor with catalyst can dissociate molecular hydrogen and then, atomic hydrogen diffuse into lattice of nano-columnar WO3 and MoO3. In the diffusion process, the interaction between hydrogen and oxides generates unpaired d-spin providing polaron effect that is formed with ion core and unpaired d electrons. Then, visible coloration that consists of plasmonic effect and a H-defect state appears from transparent to blue. The measurement of coloration is conducted with color difference (ΔE^*). In case of the Pd-WO3, hydrogen detection from 0.1 to 100 % is confirmed with fast response ΔE^*>20 and remarkable selectivity against CH4 and CO. Moreover, the sensor shows a possibility to use multi-modal sensor that involves resistance and chemochromic method. Besides, we discuss a subject to expand hydrogen applications with a precise hydrogen concentration determination by using high precise H2 concentration sensor and with hydrogen associated health applications such as hydrogen containing water.

감지 타입에 따른 FCEV용 수소센서의 감지성능 비교 평가

이영복(Youngbok Lee),이대건(Daegun Lee),박태욱(Taewook Park),심광택(Kwangtaek Shim),윤병규(ByoungGyu Yoon) 한국자동차공학회 2022 한국자동차공학회 학술대회 및 전시회 Vol.2022 No.11

In the Fuel cell electric vehicle, hydrogen sensors are mandatory to prevent the accident which is caused by hydrogen leakage. It is important for hydrogen sensors to exactly and promptly detect the hydrogen leakage of the FCEV. Thermal conductivity hydrogen sensors and catalytic combustion hydrogen sensors are widely used in automobiles like FCEV and in an industrial field. The goal of this study is to evaluate the sensing performance between a thermal conductivity hydrogen sensor and a catalytic combustion hydrogen sensor. To achieve the goal, sensing performance of those sensors is evaluated in various ambient temperature and hydrogen concentration. The result of this study was that the sensing performance of thermal conductivity hydrogen sensor is reliable in every case. But the sensing performance of catalytic combustion hydrogen sensors is decreased in low temperature conditions.

Flexible Hydrogen Sensor Using Ni-Zr Alloy Thin Film

Yun, Deok-Whan,Park, Sung Bum,Park, Yong-il Materials Research Society of Korea 2019 한국재료학회지 Vol.29 No.5

A triple-layered $PMMA/Ni_{64}Zr_{36}/PDMS$ hydrogen gas sensor using hydrogen permeable alloy and flexible polymer layers is fabricated through spin coating and DC-magnetron sputtering. PDMS(polydimethylsiloxane) is used as a flexible substrate and PMMA(polymethylmethacrylate) thin film is deposited onto the $Ni_{64}Zr_{36}$ alloy layer to give a high hydrogen-selectivity to the sensor. The measured hydrogen sensing ability and response time of the fabricated sensor at high hydrogen concentration of 99.9 % show a 20 % change in electrical resistance, which is superior to conventional Pd-based hydrogen sensors, which are difficult to use in high hydrogen concentration environments. At a hydrogen concentration of 5 %, the resistance of electricity is about 1.4 %, which is an electrical resistance similar to that of the $Pd_{77}Ag_{23}$ sensor. Despite using low cost $Ni_{64}Zr_{36}$ alloy as the main sensing element, performance similar to that of existing Pd sensors is obtained in a highly concentrated hydrogen atmosphere. By improving the sensitivity of the hydrogen detection through optimization including of the thickness of each layer and the composition of Ni-Zr alloy thin film, the proposed Ni-Zr-based hydrogen sensor can replace Pd-based hydrogen sensors.

Review of Hydrogen Gas Sensors for Future Hydrogen Mobility Infrastructure

Jun-Seo Lee,안진우,배수강,이승기 한국진공학회 2022 Applied Science and Convergence Technology Vol.31 No.4

The indiscriminate use of fossil fuels has adverse effects, such as environmental pollution and climate change. Therefore, there is growing interest in using hydrogen as an eco-friendly energy source. Among the diverse applications of hydrogen energy, hydrogen mobility has attracted considerable attention because it can compensate for the limitations of existing internal combustion engines and electricity-based mobility. To this end, relevant hydrogen-based infrastructure is being built in urban areas with rapid technological advancements. However, recent explosions of hydrogen charging stations in Norway and hydrogen storage tanks in South Korea have led to anxiety and the rejection of hydrogen application infrastructure. Therefore, to ensure the stability and safe operation of newly built infrastructure for hydrogen mobility in urban areas, an advanced system is required to improve existing technologies for hydrogen safety management. A hydrogen sensor is a front-line device for identifying initial hydrogen leaks and monitoring the status of hydrogen; thus, it is a building block for safety management systems. In this review, the operating principles and state-of-the-art hydrogen sensors are described by focusing on their suitability in hydrogen mobility applications based on the possibility of miniaturization and high hydrogen selectivity.

Recent advances on H₂ sensor technologies based on MOX and FET devices: A review

Sharma, Bharat,Sharma, Ashutosh,Kim, Jung-Sik Elsevier 2018 Sensors and actuators. B Chemical Vol.262 No.-

<P><B>Abstract</B></P> <P>The importance of metal oxide semiconductor (MOX) and field effect transistor (FET) based sensors has been increasing due to their extended practical applications for gas detection. Various investigations have confirmed that gas sensing characteristics depend on the sensitivity of the metal oxide and catalytic materials. In recent years, hydrogen gas sensor technology has been progressively more capable in practical applications. The propagation velocity of hydrogen flames is high enough to cause severe explosion over an extensive range of 4%–75% H<SUB>2</SUB>. Therefore, the use of hydrogen carries a great risk, and the requirement for its leakage detection is imperative in hydrogen generation, transportation, stockpiling, and its utilization. Usage of MOX and FETs has increased tremendously in designing precise hydrogen sensors. Therefore, in this review, the authors have focused on the recent development in MOX and FET based hydrogen sensors. MOX sensors are most widely available as commercialized ones.Also, FET-type gas sensors have many advantages, compared with traditional ones owing to their reduced shape, size, and lower production cost. Nevertheless, the processing parameters and reproducibility need to be enhanced for expanding their applications. In this review, the role of the important sensing parameters, e.g., measurement range, sensitivity, selectivity, response and recovery time, on the sensing mechanism and operation, and the most recent innovation and improvement in MOX and FET sensing technologies are discussed. Finally, we report the sensing techniques, mechanism and factors affecting the sensitivity for MOX and MOSFET type sensors.</P>

Stretchable hydrogen sensors employing palladium nanosheets transferred onto an elastomeric substrate

Namgung, Gitae,Ta, Qui Thanh Hoai,Noh, Jin-Seo Elsevier 2018 Chemical physics letters Vol.703 No.-

<P><B>Abstract</B></P> <P>Stretchable hydrogen sensors were fabricated from Pd nanosheets that were transferred onto a PDMS substrate. To prepare the Pd nanosheets, a Pd thin film on PDMS was first biaxially stretched and then PDMS substrate was etched off. The size of Pd nanosheets decreased as the applied strain increased and the film thickness decreased. A transfer technique was utilized to implement the stretchable hydrogen sensors. The stretchable sensors exhibited negative response behaviors upon the exposure to hydrogen gas. Interestingly, the sensors worked even under large strains up to 30%, demonstrating a potential as a high-strain-tolerable hydrogen sensor for the first time.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Palladium (Pd) nanosheets were prepared by a combination of biaxial stretching and PDMS delamination. </LI> <LI> The size of Pd nanosheets could be controlled by adjusting the applied strain and film thickness. </LI> <LI> Stretchable hydrogen gas sensors were fabricated using the Pd nanosheets. </LI> <LI> The stretchable sensors responded to hydrogen gas even under a 30% strain. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Pd nanosheets were prepared by biaxially stretching a Pd film on PDMS and subsequently delaminating the PDMS. It was demonstrated that stretchable hydrogen sensors fabricated from the Pd nanosheets could respond to hydrogen gas even under large strains up to 30%.</P> <P>[DISPLAY OMISSION]</P>

Highly sensitive nonpolar <i>a</i>-plane GaN based hydrogen diode sensor with textured active area using photo-chemical etching

Baik, Kwang Hyeon,Kim, Jimin,Jang, Soohwan Elsevier 2017 Sensors and actuators. B Chemical Vol.238 No.-

<P><B>Abstract</B></P> <P>In this work, a highly sensitive <I>a-</I>plane ( 11 2 ¯ 0 ) GaN (<I>a-</I>GaN) based hydrogen sensor with a large active surface area on the Schottky contact region was fabricated and characterized. By using a simple photochemical etching technique, a striated surface morphology with triangular prisms consisting of <I>m</I>-plane facets on the <I>a-</I>GaN surface was obtained. The maximum relative current change of the etched <I>a-</I>GaN diode was as high as 3.8×10<SUP>7</SUP>%, and the reduction of the effective Schottky barrier height was 0.49eV upon 4% hydrogen exposure. The photo-chemically etched <I>a-</I>GaN sensor showed a remarkably improved hydrogen response and good repeatability for cyclic exposure to hydrogen. The photo-chemically textured GaN surface with enlarged surface area increased the number of adsorption sites available for hydrogen molecules to catalytically-decompose into surface atoms, lowering the effective Schottky barrier height, thereby increasing the measured current. Furthermore, the hydrogen sensing properties of the etched <I>a</I>-GaN diodes at different values of humidity and temperature were investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photo-chemically etched <I>a-plane</I> GaN Schottky diode hydrogen sensor was developed. </LI> <LI> The etched large surface offers more active adsorption sites for hydrogen molecules. </LI> <LI> The high sensitivity of the device for hydrogen was observed up to 500°C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Pd on MoO₃ nanoplates as small-polaron-resonant eye-readable gasochromic and electrical hydrogen sensor

Kalanur, Shankara S.,Yoo, Il-Han,Seo, Hyungtak Elsevier Sequoia 2017 Sensors and actuators. B Chemical Vol.247 No.-

<P><B>Abstract</B></P> <P>Hydrogen is a renewable, efficient, and clean energy carrier that can replace petroleum as the future of energy. Eventually, efficient hydrogen detection will become an important requirement for the successful and safe use of hydrogen as a fuel. Among the various hydrogen detection schemes available, gasochromic sensors have major advantages of being intrinsically safe, free of electric contacts in the sensing area, easy to use, and inexpensive. In view of these advantages, we developed an irreversible gasochromic and electrical sensor composed of MoO<SUB>3</SUB> nanoplates and Pd nanoparticles fabricated via green deposition. The amount, distribution, and particle size of the Pd nanoparticles can be controlled easily by modifying the deposition condition, which is necessary for efficient hydrogen sensing. The developed gasochromic sensor was found to change color from white to dark blue upon hydrogen exposure, owing to the polaron-resonance effect; this effect is induced by the coupling of atomic free d-electrons in reduced Mo ion states with H+ ions. Hydrogen concentrations as low as up to 0.1% could be easily detected by the developed sensor. The simple and green fabrication process and detection scheme make the developed sensor highly cost effective and widely applicable in various areas of the hydrogen industry.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrothermal synthesis of MoO<SUB>3</SUB> nanoplates. </LI> <LI> Green deposition of Pd on MoO<SUB>3</SUB> nanoplates. </LI> <LI> Polaron-Resonant Eye readable hydrogen gas sensor. </LI> <LI> Mechanism of sensing is presented. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

수소가스 유량 변화에 따른 센서 칩에서의 센싱감도 및 열특성 연구

서호철(Ho-Cheol Suh),조용준(Yong-Jun Cho),박경석(Kyoung-Suk Park) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11

Even though hydrogen is an environment-friendly energy source, safety and effectiveness issues in storage, transportation, and usage of hydrogen should be clearly resolved in every application. Thus, sensors for detecting hydrogen leakage, especially for automotive hydrogen fuel cell systems, should be designed to have much higher resolution and accuracy in comparison with conventional gas sensors. In the present study, the performance of a combustion type micro chip hydrogen sensor for fuel cell electric vehicle is optimized by investigating the effect of flow rate of hydrogen on the resolution of the micro chip hydrogen sensor is investigated.. Prototypic sensors with detection element and compensation element were fabricated to have five different resistances (40Ω, 60Ω, 80Ω, 100Ω, 120Ω) of heaters. At the given hydrogen flow rates 3.3 ~ 16.5 cm3/s, the effect of the hydrogen flow rate on the temperature change of detection and compensation elements, and the sensitivity of the sensor is insignificant.