(25a) Proton-Conducting Oxide Thin Film Coated Fiber Optic Sensor for High Temperature Hydrogen Monitoring

We report the integration of nanocrystalline perovskite thin film with a structured optical fiber for in situ monitoring of bulk hydrogen in conditions relevant to the H₂ production by biomass and fossil fuel gasification and water gas shift (WGS) processes. Hydrogen production from renewable bio-renewable and fossil stocks is in the center of the development of clean power systems. The key constituents in the syngas by gasification include H₂, CO, CO₂, H₂O, light hydrocarbons (i.e. CH₄ etc.), and common impurity H₂S. The ability of in situ gas monitoring is imperative to the realization of intelligent process control for improving the energy efficiency, system reliability, and pollutant emission reduction. However, currently available semiconductor and electrochemical sensors are difficult to deploy and operate directly in the harsh environment involving high temperature, corrosive and dusty gases.

In this study, the proton electron/hole mixed conducting perovskite-type Sr(Ce_0.8Zr_0.1)Y_0.1O_2.95 (SCZY) nanocrystalline thin film was synthesized by a facile polymeric precursor route on the long-period fiber grating (LPFG). At high temperature, the defect states in the SCZY crystal lattice change upon reacting with hydrogen that varies its refractive index and light absorbing characteristics. The transmission spectrum of the LPFG is a sensitive function of refractive index of the overcoat (n^ov). The SCZY-coated LPFG can thus detect hydrogen by straightforward measurement of its resonant wavelength (λ _R) shift. The sensor's H₂-selectivity, sensitivity, stability, and reversibility have been investigated at 500 ^OC and atmospheric pressure in binary and multicomponent gas streams.