Fig. 1. Schematic of optical hydrogen sensor based on Pd-decorated multilayer hBN film

Fig. 2. Schematic of hydrogen detection principle

Fig. 3. Deformation of diaphragm at different positions under pressure

Fig. 4. Relationship between the central point deformation and the geometric parameters of the diaphragm

Fig. 5. Schematic of optical hydrogen sensor preparation based on Pd-decorated hBN film

Fig. 6. Initial reflection spectrum of optical hydrogen sensor

Fig. 7. Schematic of the hydrogen sensor detection platform

Fig. 8. Spectra of adsorption and desorption process varing with time at 0.10% H₂ volume fraction. (a) Adsorption process; (b) desorption process

Fig. 9. Sensor quantitative test result. (a) Reflection spectra at different H₂ volume fraction; (b) dip wavelength versus the hydrogen volume fraction

Fig. 10. Three cycle tests with a hydrogen volume fraction of 0.10%

Fig. 11. Relationship between wavelength shift and temperature. (a) Spectral drift at different temperatures; (b) linear fitting result