Multimode radial acoustic field excitation for ultrafast and sensitive photoacoustic detection of hydrogen and hydrocarbons

Hydrogen (H₂) and hydrocarbon gases are highly flammable in H₂ energy systems, requiring real-time monitoring with high sensitivity and rapid response. However, conventional gas sensors often suffer from slow response, cross-interference, and limited sensitivity. Here, we report a dual-gas detection system based on multimode photoacoustic spectroscopy in a piezoelectric tube, combined with a beat-frequency strategy. High-order radial acoustic modes are excited to enhance the sensitivity of H₂ detection, while the photoacoustic response enables simultaneous measurement of acetylene (C₂H₂). A 29-fold sensitivity enhancement is achieved for higher-order modes compared to the fundamental mode. The system demonstrates a frequency sensitivity of 240.1 Hz/% and a minimum detection limit (MDL) of 170.76 ppm for H₂, along with a detection limit of 13.56 ppb for C₂H₂. By introducing beat-frequency detection, the single-shot measurement time for H₂ is reduced to 15 ms, with an improved MDL of 7.39 ppm. This approach enables ultrafast, sensitive, and interference-resistant gas detection, offering a promising route for real-time multi-gas monitoring in H₂ energy applications.