Palladium and platinum-based nanoparticle functional sensor layers and integration with engineered filter layers for selective H2 sensing
Inventors
Ohodnicki, Jr., Paul R • Sun, Chenhu • Baltrus, John P • Brown, Thomas D
Assignees
Publication Number
US-10345279-B1
Publication Date
2019-07-09
Expiration Date
2035-10-20
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Abstract
The disclosure relates to a method for H2 sensing in a gas stream utilizing a hydrogen sensing material. The hydrogen sensing material is comprised of Pd-based or Pt-based nanoparticles having an average nanoparticle diameter of less than about 100 nanometers dispersed in an inert matrix having a bandgap greater than or equal to 5 eV, and an oxygen ion conductivity less than approximately 10−7 S/cm at a temperature of 700° C. Exemplary inert matrix materials include SiO2, Al2O3, and Si3N4 as well as modifications to modify the effective refractive indices through combinations and/or doping of such materials. Additional exemplary matrix materials consist of zeolitic and zeolite-derivative structures which are microporous and/or nanoporous such as the alumino-silicates and the dealuminated zeolite NaA structures. Additional sensing layers may be comprised of (1) a single “nanocomposite” layer comprised of Pd- or Pt-based particles dispersed within an inert matrix, (2) multi-layered sensing layers comprised of a nanocomposite layer with a filter overlayer, (3) core-shell layers comprised of matrix materials surrounding a core of Pd-based or Pt-based nanoparticles, and any combinations of the above.
Core Innovation
The invention relates to a method for sensing hydrogen (H2) concentration in a gas stream by using a hydrogen sensing material composed of Pd-based or Pt-based nanoparticles dispersed in an inert matrix. The inert matrix has a bandgap of at least 5 eV and very low oxygen ion conductivity at high temperatures, such as 700° C. This material produces an optical signal upon illumination by light, where the signal—comprising transmitted, reflected, or scattered light—varies with the hydrogen concentration in the gas.
The hydrogen sensing material configurations include single nanocomposite layers with Pd- or Pt-based nanoparticles dispersed within an inert matrix, multilayer sensing layers combining such nanocomposite layers with filter overlayers, and core-shell layers where nanoparticles are encapsulated by matrix materials. The inert matrix offers intrinsic filtering to improve H2 selectivity, chemical protection for nanoparticles in harsh environments, compatibility with optical waveguides due to refractive index similarity, and controlled tunability of sensing layer thickness for device optimization.
The problem addressed is the critical need for selective hydrogen sensing in applications spanning energy, defense, aviation, and aerospace, especially for accurate leak detection at concentrations up to the lower explosive limit. Existing methods face challenges including cross-sensitivity to other gases, limitations of continuous Pd films at high temperatures, and the need for sensor longevity and safety in harsh environments. Current optical sensors based on Pd thin films or nanoparticles have limitations in stability, sensitivity, and selectivity when exposed to complex gas mixtures or elevated temperatures. This invention seeks to overcome these issues by employing nanoparticle-in-matrix composites with engineered filter layers to enhance sensitivity, selectivity, and thermal stability while being compatible with optical sensing platforms.
Claims Coverage
The claims include one independent claim directed to a method for evaluating hydrogen concentration using a hydrogen sensing material and one independent claim directed to a hydrogen sensing method incorporating an overlayer filter and optical waveguide integration. The inventive features pertain to the composition and structure of the sensing material, its optical interrogation, and system integration.
Hydrogen sensing material composition
A hydrogen sensing material comprising Pd-based and/or Pt-based nanoparticles with average diameters under about 100 nm dispersed in an inert matrix stable at gas stream temperature. The matrix has a bandgap ≥5 eV and oxygen ion conductivity <10⁻⁷ S/cm at 700° C. The nanoparticles include palladium, platinum, or their alloys such as palladium-silver or platinum-silver alloys, with metallic content ≥50 wt. % in the nanoparticles.
Use of an overlayer filter to improve selectivity
Application of an overlayer of a matrix material, including zeolitic or zeolite-derived structures such as dealuminated zeolites, as a filter layer on top of the hydrogen sensing material to improve sensor response and gas selectivity by molecular sieving.
Integration with optical waveguides
Method involving placing the hydrogen sensing material in contact with an optical waveguide core material, illuminating it via incident light coupled into the core that generates an evanescent wave in the sensing material, enabling optical interrogation of hydrogen concentration based on transmitted, reflected, or scattered light.
Monitoring optical signals for hydrogen evaluation
Illuminating the hydrogen sensing material with a light source and collecting exiting light to monitor an optical signal using optical spectroscopy. The optical signal is compared between incident and exiting light to evaluate hydrogen concentration by detecting shifts indicative of hydrogen levels in the gas stream.
The claims collectively cover a method for hydrogen sensing that combines Pd- or Pt-based nanoparticles dispersed in a high bandgap inert matrix, optionally with a zeolitic filter overlayer, along with illumination and optical signal monitoring using waveguide-based optical systems for selective, sensitive, and thermally stable hydrogen detection.
Stated Advantages
Improved hydrogen selectivity due to the filtering function of the inert matrix and overlayer filter layers, minimizing cross-sensitivity to gases such as CO.
Enhanced chemical inertness and protection of Pd- and Pt-based nanoparticles in harsh and high temperature environments.
Compatibility with optical waveguide sensors owing to the low and tunable refractive index of the inert matrix, enhancing integration potential.
Controlled tunability of nanoparticle density and sensing layer thickness for optimized sensor response and device design.
Improved stability of nanoparticle size and microstructure under elevated temperatures and hydrogen cycling.
Documented Applications
Hydrogen leak detection up to the lower explosive limit (~4% H2 in air) for energy, defense, aviation, and aerospace applications.
Monitoring hydrogen in high temperature metallurgical processes and fuel gas streams for power generation technologies such as gas turbines and solid oxide fuel cells.
Dissolved hydrogen concentration measurements in transformer oils to support condition-based monitoring and early fault detection.
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