Ensuring regulatory compliance and safety in aged fuel cell Stacks through Dual-Mode hydrogen recovery

Abstract

Fuel cell electric vehicles (FCEVs) encounter critical safety challenges due to hydrogen crossover through aging polymer electrolyte membranes, leading to hazardous hydrogen accumulation during shutdown and subsequent emissions during startup that can exceed regulatory limits. This study introduces a novel dual-mode operation strategy that enables the fuel cell stack to alternate between the polymer electrolyte fuel cell mode and the electrochemical hydrogen pump (EHP) mode, actively transferring the accumulated hydrogen from the air side to the fuel side during startup. Comprehensive testing of an aged fuel cell system revealed air-side hydrogen concentrations of 33.8 vol% after 1,344 s of shutdown, highlighting the severity of hydrogen crossover in degraded membranes. Through systematic optimization using sigmoid modeling and experimental validation, a 3-s EHP operation with low-resistance configuration (9.3 Ω) was determined to provide the best balance between hydrogen transfer efficiency and system protection, preventing membrane degradation. Real-world validation demonstrated the strategy’s critical impact. Without EHP intervention, the 3-s average start-up emission was 4.2 vol%, exceeding the 4.0 vol% regulatory limit stipulated by Global Technical Regulation No. 13. Impressively, the optimized EHP operation achieved a 32 % reduction, bringing this emission down to 2.9 vol% and thus into full regulatory compliance with a substantial 28 % safety margin. The instantaneous peak emission was also significantly reduced by 42 % from 6.5 vol% to 3.7 vol%. This dual-mode operation strategy thus successfully transforms a non-compliant, end-of-life fuel cell system into a safe and regulatory-compliant one, while recovering otherwise wasted hydrogen fuel, providing a robust solution for extending the operational lifetime of FCEVs and enhancing the safety and sustainability of hydrogen mobility.