Perovskite-Type Oxide Thin Film Integrated Fiber Optic Sensor for High-Temperature Hydrogen Measurement

Small size fiber optic devices integrated with chemically sensitive photonic materials are emerging as a new class of high-performance optical chemical sensor that have the potential to meet many analytical challenges in future clean energy systems and environmental management. Here, we report the integration of a proton conducting perovskite oxide thin film with a long-period fiber grating (LPFG) device for high-temperature in situ measurement of bulk hydrogen in fossil- and biomass-derived syngas. The perovskite-type Sr(Ce0.8Zr0.1)Y0.1O2.95 (SCZY) nanocrystalline thin film is coated on the 125 μm diameter LPFG by a facile polymeric precursor route. This fiber optic sensor (FOS) operates by monitoring the LPFG resonant wavelength (λR), which is a function of the refractive index of the perovskite oxide overcoat. At high temperature, the types and population of the ionic and electronic defects in the SCZY structure depend on the surrounding hydrogen partial pressure. Thus, varying the H2 concentration changes the SCZY film refractive index and light absorbing characteristics that in turn shifts the λR of the LPFG. The SCZY-coated LPFG sensor has been demonstrated for bulk hydrogen measurement at 500 °C for its sensitivity, stability/reversibility, and H2-selectivity over other relevant small gases including CO, CH4, CO2, H2O, and H2S, etc.