Optical Hydrogen Sensor Research Articles

Pt/MOF-5 film-coated optical micro-nano fibre hydrogen sensor with humidity and temperature compensation functions

Pt/MOF-5 film-coated optical micro-nano fibre hydrogen sensor with humidity and temperature compensation functions

Pd/PMMA Nanocomposite-Coated Optical Fiber Hydrogen Sensor Operating at Room Temperature With Humidity Tolerance

Pd/PMMA Nanocomposite-Coated Optical Fiber Hydrogen Sensor Operating at Room Temperature With Humidity Tolerance

Thin Film TaFe, TaCo, and TaNi as Potential Optical Hydrogen Sensing Materials.

This paper studies the structural and optical properties of tantalum-iron-, tantalum-cobalt-, and tantalum-nickel-sputtered thin films both ex situ and while being exposed to various hydrogen pressures/concentrations, with a focus on optical hydrogen sensing applications. Optical hydrogen sensors require sensing materials that absorb hydrogen when exposed to a hydrogen-containing environment. In turn, the absorption of hydrogen causes a change in the optical properties that can be used to create a sensor. Here, we take tantalum as a starting material and alloy it with Fe, Co, or Ni with the aim to tune the optical hydrogen sensing properties. The rationale is that alloying with a smaller element would compress the unit cell, reduce the amount of hydrogen absorbed, and shift the pressure composition isotherm to higher pressures. X-ray diffraction shows that no lattice compression is realized for the crystalline Ta body-centered cubic phase when Ta is alloyed with Fe, Co, or Ni, but that phase segregation occurs where the crystalline body-centered cubic phase coexists with another phase, as for example an X-ray amorphous one or fine-grained intermetallic compounds. The fraction of this phase increases with increasing alloyant concentration up until the point that no more body-centered cubic phase is observed for 20% alloyant concentration. Neutron reflectometry indicates only a limited reduction of the hydrogen content with alloying. As such, the ability to tune the sensing performance of these materials by alloying with Fe, Co, and/or Ni is relatively small and less effective than substitution with previously studied Pd or Ru, which do allow for a tuning of the size of the unit cell, and consequently tunable hydrogen sensing properties. Despite this, optical transmission measurements show that a reversible, stable, and hysteresis-free optical response to hydrogen is achieved over a wide range of hydrogen pressures/concentrations for Ta-Fe, Ta-Co, or Ta-Ni alloys which would allow them to be used in optical hydrogen sensors.

Advancing Hydrogen Sensing for Sustainable Aviation: A Metal Hydride Coated TFBG Optical Fibre Hydrogen Sensor

The aviation industry is undergoing a significant shift toward sustainability, with hydrogen emerging as a promising green fuel to reduce carbon emissions due to its high gravimetric energy density and clean combustion exhaust compared to traditional aviation fuels. However, realizing hydrogen's aviation potential requires advanced sensors to ensure safety and efficiency in challenging environments, particularly for monitoring hydrogen near high-temperature engines and cryogenic storage tanks. Fibre optic sensors offer an exceptional advantage in these demanding conditions due to their capacity to operate in harsh environments, their small size, immunity to electromagnetic interference, spark-free operation, and remote sensing capabilities. Metal hydrides are prominent sensing materials studied for hydrogen sensing, especially palladium (Pd). Nonetheless, existing literature pertaining to Pd-coated fiber optic sensors for hydrogen detection has brought to light concerns regarding response hysteresis, stability, and linearity of Pd hydrogen sensors, calling for innovative solutions. In response to these challenges, our research introduces an innovative fibre optic hydrogen sensor, introducing tantalum (Ta) based metal hydrides as the sensing material. The sensor's construction involved the deposition of a nanometer-thick Ta thin film onto the surface of a tilted fibre Bragg grating (TFBG) using a magnetron sputtering technique. The sensing mechanism relies on the modulation of optical constants of the Ta thin film in response to even minute hydrogen concentrations, culminating in spectral changes in the transmission spectrum of the TFBG. In this proof of concept work, changes in both amplitude and the centre wavelength of cladding resonances of the TFBG transmission spectrum were observed in the hydrogen concentration range from 0.01% to 4% at room temperature. These initial findings underscore the substantial potential of our approach in developing highly sensitive and robust fibre-optic hydrogen sensors tailored specifically for hydrogen-powered aviation.

Quasi-distributed optical fiber hydrogen leakage detecting system based on bus chain topology structure

Micro-mirror optical fiber hydrogen sensors have the advantages of compact structure and fast demodulation speed. All-optical sensor networks consisting of micro-mirror optical fiber hydrogen sensors are essentially necessary across the hydrogen value chain. A bus chain topology structure hydrogen leakage detecting system based on micro-mirror sensors is proposed and experimentally demonstrated. A compensating optical path with constant power supply is introduced, and the power dissipation scheme is theoretically and experimentally proposed by designating the splitting ratios of the splitters array. By constructing such a network with twenty micro-mirror hydrogen sensors, the system has been experimentally verified with good repeatability and stability under different concentrations of hydrogen. By employing this bus chain topology strategy, a quasi-distributed optical fiber hydrogen leakage detection system with micro-mirror hydrogen sensors array is realized. It will provide a promising solution with high feasibility on multi-point leakage detecting in hydrogen infrastructures.

Neural network enabled nanoplasmonic hydrogen sensors with 100 ppm limit of detection in humid air

Environmental humidity variations are ubiquitous and high humidity characterizes fuel cell and electrolyzer operation conditions. Since hydrogen-air mixtures are highly flammable, humidity tolerant H2 sensors are important from safety and process monitoring perspectives. Here, we report an optical nanoplasmonic hydrogen sensor operated at elevated temperature that combined with Deep Dense Neural Network or Transformer data treatment involving the entire spectral response of the sensor enables a 100 ppm H2 limit of detection in synthetic air at 80% relative humidity. This significantly exceeds the <1000 ppm US Department of Energy performance target. Furthermore, the sensors pass the ISO 26142:2010 stability requirement in 80% relative humidity in air down to 0.06% H2 and show no signs of performance loss after 140 h continuous operation. Our results thus demonstrate the potential of plasmonic hydrogen sensors for use in high humidity and how neural-network-based data treatment can significantly boost their performance.

Hydrogen and temperature measurement using a functionalized superstructure of Bragg gratings in a helical-core fiber

As decarbonization is urgent in global climate, hydrogen, of which the product is pure water after burning, becomes a potentially clean and sustainable energy source as a replacement for fossil fuels. However, the hydrogen storge is challenging due to the highly flammable and explosive properties, limiting its enormous applications in industries. Real-time and sensitive detection of hydrogen is thus imperative to avoid leakage accidents, while the sensors based on electric signals have the risk of spark or arc discharge which may induce explosion. Here, we propose and experimentally demonstrate an optical hydrogen sensor using a functionalized superstructure of Bragg gratings in a helical-core fiber with a thin palladium film. Due to the cross sensing of the two sets of gratings, simultaneous detection of hydrogen concentration and temperature can be realized. By modifying the device diameter using wet etching technique, the sensitivity of hydrogen concentration is enhanced by 2.7 times. The utilization of the superstructure of Bragg gratings sampled in the helical-core fiber provides a promising platform for reliable and safe sensing of hydrogen with the ability of simultaneous monitoring of temperature.

Ultrafast and Repeatable Optical Fiber Hydrogen Sensor With Urchin-Like Nanospheres Functionalization

Ultrafast and Repeatable Optical Fiber Hydrogen Sensor With Urchin-Like Nanospheres Functionalization

Sensitive and Repeatable Optical Fiber Hydrogen Sensors Using Plasma-induced Oxygen Vacancies Magnetron Sputtering Coating Technique

Sensitive and Repeatable Optical Fiber Hydrogen Sensors Using Plasma-induced Oxygen Vacancies Magnetron Sputtering Coating Technique

Block copolymer-templated gasochromic WO3 thin films with uniform mesopores for fast optical hydrogen sensing

A method to prepare mesoporous WO3 thin films (represented by MP-WO3) with a uniform pore size of ∼18 nm is developed successfully by utilizing poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as the structure-directing agent (SDA). The properties of the gasochromic MP-WO3 thin film are studied in detail and compared with the control groups prepared by using homopolymer PEO, PS, or their mixtures as SDA. Utilizing an optimized thermal treatment procedure, the gasochromic MP-WO3 thin film of which the transmittance change ΔT is 59.1% exhibites the fastest coloration and bleaching speed with a coloration time of 27.3 s and a bleaching time of 19.7s as well as excellent reversibility within 90 cycles. This study offers a new strategy and insight into the development of mesoporous WO3 hydrogen gasochromic films with excellent performances and paves its way toward the application of an optical hydrogen sensor.

Optical fiber evanescent hydrogen sensor based on palladium nanoparticles coated Bragg gratings

Optical fiber evanescent hydrogen sensor based on palladium nanoparticles coated Bragg gratings

High Sensitivity Hydrogen Sensors Based on Optical Micro/Nanofiber Couplers Working at the Dispersion Turning Point

The safe utilization of hydrogen as a clean fuel and industry material requires the reliable detection of gas leakage. Thus, hydrogen sensors with high sensitivity and fast response are in urgent demand. Optical hydrogen sensors are especially attractive among various hydrogen detection techniques because of their intrinsic safety. Herein, a high-sensitivity hydrogen gas sensor is proposed based on optical micro/nanofiber couplers working at the dispersion turning point. The Pd coatings used were deposited on the waist region by magnetron sputtering. Due to the phase transition of palladium in the presence of hydrogen, intensity changes in the optical transmission of the devices are produced. It is demonstrated that the proposed platform provides high sensitivity, good repeatability, and selectivity, together with a fast response time for hydrogen detection below the explosive concentration. The response and recovery times are ~20 and ~28 seconds, respectively. The detected hydrogen concentration range is 0.1-1.5% (in volume). The detection limit of this sensor is below 0.1%.

Improved performance of fiber-optic hydrogen sensor of porous Pt/WO3 based on ZIF-8

A novel fiber-optic hydrogen sensor including Pt/WO3 sensing material with a microporous structure is proposed and experimentally demonstrated with improved performance. The proposed Pt/WO3 sensing material is realized by introducing metal-organic frameworks (MOFs) as templates. The mesoporous structure of the ZIF-8 template improves the reactive sites of hydrogen sensitive materials with hydrogen. Hydrogen sensors were fabricated by combining the synthesized material with Fiber Bragg Gratings (FBGs) and the performance of hydrogen sensors was investigated. The experimental results show that the hydrogen sensitivity of the FBG with ZIF-8 synthesized Pt/WO3 has been increased to 0.075 pm/ppm, which is twice that without ZIF-8 synthetization. The stability and the response speed are also significantly improved. The introduction of microporous MOFs templates into Pt/WO3 sensing material will greatly accelerate the wide application of Pt/WO3-based fiber optic hydrogen sensors on hydrogen leakage detection.

Promoting the discoloration of PdO in low concentration H2 by using PdAu bimetallic catalyst for eye-readable hydrogen leakage detection

Developing reliable and low-cost optical hydrogen sensors for hydrogen leakage detection at room temperature is extremely important. It requires that hydrogen sensors have a remarkable and rapid color change in low concentration H2/air mixtures, which it is still quite challenging at present. Herein, we demonstrate an eye-readable hydrogen sensor based on Pd-decorated Au@PdO core-shell nanoparticle arrays (Pd-Au@PdO NAs). Pd-Au@PdO NAs show an obvious color change from brownish-yellow to yellow-gray in 1 v/v% H2/air and gray in 4 v/v% H2/air, with ΔE values of 8.1 and 22.5, respectively. Detailed investigation showed that, at the cracks of PdO shell where Au core is exposed, PdAu bimetallic catalyst is generated during the sample-synthesis process. Compared with Pd catalyst, PdAu bimetallic catalyst significantly prompts the reduction of PdO in low concentration H2, represented as a faster discoloration process and more obvious color change. Additionally, the core-shell structure ensures a long-term stability through protecting the PdAu catalyst. We further show that the irreversible sensing performance of Pd-Au@PdO NAs can be reactivated repeatedly, which favors extending the lifetime of the optical sensor and reducing the cost.

Tunable Fabry–Pérot Resonator with Dynamic Structural Color: A Visual and Ultrasensitive Hydrogen Sensor

Hydrogen detection is crucial for the forthcoming hydrogen economy. Here, we present a visual, ultrasensitive, optical hydrogen sensor based on a tunable Fabry-Pérot (FP) resonator, which can fully release the volume expansion of palladium during hydrogenation and transfer this volume expansion into an optical signal. The FP resonator consists of a suspended polymethylmethacrylate/palladium (PMMA/Pd) bilayer on a gold (Au) square-hole array. The bottom of the gold square hole and hydrogen-sensitive PMMA/Pd bilayer form a dynamically tunable FP resonator. When hydrogen gas (H2) is loaded, the hydrogen-induced lateral expanding stress concavely deforms the suspended bilayer downward to the substrate, narrowing the metal-air-metal gap at the center of the hole, and finally leading to a spectral blue shift. Our experimental results show a giant spectral shift of 279 nm with a reflectance variation of 57% on exposure to 0.6% H2 mixed with air. Such an ultrahigh optical response results in a significant color change, enabling visual hydrogen detection. In addition, the sensor has a H2 detection limit down to 0.1% and good recyclability. These advantages indicate that the sensor has excellent potential for hydrogen sensing applications.

Tuning the Properties of Thin-Film TaRu for Hydrogen-Sensing Applications

Accurate, cost-efficient, and safe hydrogen sensors will play a key role in the future hydrogen economy. Optical hydrogen sensors based on metal hydrides are attractive owing to their small size and costs and the fact that they are intrinsically safe. These sensors rely on suitable sensing materials, of which the optical properties change when they absorb hydrogen if they are in contact with a hydrogen-containing environment. Here, we illustrate how we can use alloying to tune the properties of hydrogen-sensing materials by considering thin films consisting of tantalum doped with ruthenium. Using a combination of optical transmission measurements, ex situ and in situ X-ray diffraction, and neutron and X-ray reflectometry, we show that introducing Ru in Ta results in a solid solution of Ta and Ru up to at least 30% Ru. The alloying has two major effects: the compression of the unit cell with increasing Ru doping modifies the enthalpy of hydrogenation and thereby shifts the pressure window in which the material absorbs hydrogen to higher hydrogen concentrations, and it reduces the amount of hydrogen absorbed by the material. This allows one to tune the pressure/concentration window of the sensor and its sensitivity and makes Ta1-yRuy an ideal hysteresis-free tunable hydrogen-sensing material with a sensing range of >7 orders of magnitude in pressure. In a more general perspective, these results demonstrate that one can rationally tune the properties of metal hydride optical hydrogen-sensing layers by appropriate alloying.

Recent Advances in Optical Hydrogen Sensor including Use of Metal and Metal Alloys: A Review

Optical sensing technologies for hydrogen monitoring are of increasing importance in connection with the development and expanded use of hydrogen and for transition to the hydrogen economy. The past decades have witnessed a rapid development of optical sensors for hydrogen monitoring due to their excellent features of being immune to electromagnetic interference, highly sensitive, and widely applicable to a broad range of applications including gas sensing at the sub-ppm range. However, the selection of hydrogen selective metal and metal alloy plays an important role. Considering the major advancements in the field of optical sensing technologies, this review aims to provide an overview of the recent progress in hydrogen monitoring. Additionally, this review highlights the sensing principles, advantages, limitations, and future development.

A dual-band hydrogen sensor based on Tamm plasmon polaritons.

Optical hydrogen sensors possess significant potential in various fields, including aerospace and fuel cell applications, which is due to their compact design and immunity to electromagnetic interference. However, commonly used sensors mostly use single-band sensing, which increases the risk of inaccurate measurements due to environmental interference or operational errors. To address this issue, this study proposes a dual-band hydrogen sensor comprising a Pd metal layer, a dielectric spacer layer, a defect layer, and a photonic crystal. By leveraging the interaction between the defect mode in the excitonic microcavity structure and the Tamm plasmon polaritons (TPPs) and Fabry-Perot (FP) resonances, the structure simultaneously generates two near-zero resonance valleys in the visible wavelength range. By adjusting the thickness of the defect layer, the coupling effect of the defect mode and TPPs together with FP resonance respectively is optimized. When the thickness is 0.27 μm, the sensitivities of the Tamm resonance band and FP resonance band are 239 and 21 RIU-1, respectively. Compared with the common sensors with a single band, its low-sensitivity wavelength can be used as a reference to assist the high-sensitivity wavelength for sensing. In addition, we find that the proposed sensor, through calculation, has good fault tolerance for both the thickness of the defect layer and the incident light angle. This study demonstrates a dual-band hydrogen sensor with TPPs, which is important for exploring new optical hydrogen sensors.

Lateral Offset Single-Mode Fiber-Based Fabry-Perot Interferometers with Vernier Effect for Hydrogen Sensing.

A high-sensitive optical fiber hydrogen (H2) sensor with Vernier effect by cascading three Fabry-Perot interferometers (FPIs) has been proposed. It is prepared by welding three sections of a single-mode fiber with a lateral offset structure and coating polydimethylsiloxane (PDMS) at the offset part to form three cascaded FPIs and generate a Vernier envelope spectrum. To realize H2 sensing, the hydrogen-sensitive material Pd/WO3 is fabricated and coated on the outside of the PDMS. Pd/WO3 will generate local heat when in contact with H2, which will cause the thermal expansion and refractive index change of PDMS and finally lead to the Vernier envelope wavelength shifting with the change of H2 concentration. Due to the Vernier effect, the H2 sensor can achieve a linear measurement sensitivity of 6.214 nm/% in the concentration range of 0-1%, which is 16.11 times that of a single FPI. The proposed H2 sensor possesses advantages of high sensitivity, easy preparation, compact structure, low cost, and easy long-distance transmission.

Optical fiber hydrogen sensor based on self-assembled PDMS/Pd-WO3 microbottle resonator

In this paper, a new optical fiber hydrogen(H2) sensor based on a self-assembled microbottle resonator was proposed. The self-assembled microbottle was simply obtained by coating the single-mode fiber (SMF) with an internal composite material layer of palladium-tungsten trioxide (Pd-WO3) that was sensitive to H2 and an outer organic polymer material layer of polydimethylsiloxane (PDMS) with a significant thermal response. The microbottle resonator was further fabricated by coupling a tapered fiber with the self-assembled microbottle to excite whispering gallery mode (WGM). When the WGM resonator is exposed to H2, H2 molecules penetrate the PDMS and undergo redox reaction with the Pd-WO3. After the PDMS absorbs the reaction heat, its volume and refractive index will change, along with the wavelength shift of the WGM resonator. Therefore, a simple and low-cost H2 sensor is realized by observing the shift of resonance wavelength. Experimental results showed that the hydrogen sensor had a maximum sensitivity of − 3.091 nm/% at 25 ℃. And the resonance wavelength just shifted a small distance when the relative humidity increased from 22.87 % to 84.59 % or the temperature rose from 20.2 ℃ to 30 ℃, which indicated the sensor had preferable resistance to disturbances of external humidity and temperature.