Investigation of CO2 bubble behavior and performance in air-breathing direct methanol fuel cells with spiral-patterned anode flow field

Understanding the behavior of CO2 bubbles in the anode compartment is essential for improving the performance of air-breathing direct methanol fuel cells (DMFCs). This study investigates CO2 bubble dynamics in the anode compartment of DMFCs using the Volume of Fluid (VOF) numerical method. The model incorporates a uniform pore catalyst layer (CL), a structured gas diffusion layer (GDL), and a single spiral-patterned anode flow field plate. Experimental validation was conducted using video image processing and pressure drop measurements. The findings reveal that CO2 bubble volume fractions emerge at the edges and corners of the CL from 0.01 s onward, spreading unevenly toward the spiral pattern's center. In the GDL, CO2 bubbles increasingly concentrate toward the center beginning at 0.06 s. Significant bubble accumulation in the flow field channels was observed between 0.06 and 0.09 s. The interdependence of bubble dynamics across the CL, GDL, and flow fields was strongly influenced by the direction of reactant flow. Numerical results aligned with experimentally observed CO2 bubble distributions in the spiral flow field channels. The designed DMFC demonstrated a peak power density of 12.6 mW/cm2, showcasing effective CO2 gas management and improved fuel utilization. The Present study introduced a novel methodology for optimizing DMFC systems using enhanced CO2 handling strategies.