Operando Monitoring of Bubble Dynamics in PEM Water Electrolyzers Using Tilted Fiber Bragg Grating Sensors

Understanding the bubble evolution dynamics under operating conditions is critical for a comprehensive performance assessment of water electrolysis systems. However, real-time microscale monitoring of bubble dynamics evolution within these systems remains a significant technical challenge, constrained by their enclosed nature and highly corrosive environments. To address this, we developed an operando monitoring system for internal bubble states in proton exchange membrane water electrolyzers (PEMWEs) utilizing a tilted fiber Bragg grating (TFBG) sensor. By inserting the miniaturized TFBG sensor into the channel of the PEMWE, we achieved monitoring of bubble nucleation, growth, and detachment states under operational conditions. This noninvasive operando monitoring approach established a quantitative relationship model between TFBG transmission spectra with bubble states and thus realized real-time tracking of bubble evolution and population change through continuous spectral inquiry of TFBG cladding-mode resonance. This study is expected to provide theoretical and experimental support for PEMWE structural design and performance optimization.