CO Cross-Interference Characteristics of a Pd-Cu Fiber-Optic MEMS Hydrogen Sensor for Early Warning of Thermal Runaway in Energy Storage Batteries

In early-warning scenarios for thermal runaway in energy storage batteries, carbon monoxide (CO) may interfere with hydrogen detection and reduce the reliability of signal interpretation. To mitigate CO cross-interference under representative mixed-gas conditions and improve sensing stability, a fiber-optic microelectromechanical systems (MEMS) hydrogen sensor based on a Pd-Cu alloy-sensitive layer was developed. The sensor employs a single-cantilever structure and a reflective Fabry-Pérot (F-P) interferometer for optical readout. Comparative experiments were carried out using sensors coated with pure Pd and Pd-Cu-sensitive layers under pure H₂, CO background interference, and temperature-fluctuation conditions. The Pd-Cu sensor exhibited a good linear response over 0-500 ppm H₂, with a sensitivity of 0.0845 nm/ppm. Under a mixed atmosphere of 200 ppm H₂ and 500 ppm CO, the Pd-Cu sensor measured 198 ppm, whereas the pure Pd sensor measured 176 ppm, corresponding to relative errors of approximately 1% and 12%, respectively. In addition, the Pd-Cu sensor showed faster response/recovery behavior and better output stability after temperature compensation. These results indicate that, under the investigated conditions, the selected Pd-Cu-sensitive layer can effectively reduce CO-induced interference and improve the accuracy and stability of fiber-optic MEMS hydrogen sensing, supporting its feasibility for representative early-warning-related monitoring scenarios in energy storage batteries.