Effects of bolt torque and gasket geometric parameters on open-cathode polymer electrolyte fuel cells

Open-cathode polymer electrolyte fuel cells with compact design have attracted increasing attention in the field of portable energy equipment. In view of the open cathode design, these cells usually exhibit large ohmic and mass transfer resistances. Such resistances can be reduced by using optimized bolt torque as well as gasket. The present study explores the effects of bolt torque and gasket geometric parameters on cell performance based on various measurements of polarization curve, high-frequency impedance, electrochemical impedance spectroscopy, and pressure distribution indentation. Remarkably, a performance improvement of 20.1% is achieved with the increase of torque (1.0–5.0 N·m) due to the decrease of ohmic resistance. However, excess torque (5.5 N·m) results in a 1.3% power reduction due to the increased mass transfer resistance. For the gasket of the cell, reducing the gasket thickness (0.65–0.48 mm) and width (2.5–1.5 mm) leads to the decrease of ohmic resistance and improvement of the cell performance by 3.4%~11.1%. However, the gasket with the minimum thickness (0.40 mm) suffers from a serious mass transfer issue. The relationship between the GDL compression, gasket, and sealing groove is quantitatively introduced to explain how the geometric parameters of the gasket affect the cell performance. Additionally, the longitudinal and transverse deformation of the gasket is considered. It is concluded that the applied torque, GDL compression, gasket, and sealing groove should be reasonably matched to reduce the ohmic resistance and avoid mass transfer limitation.