Analysis of the clamping effects on the passive direct methanol fuel cell performance using electrochemical impedance spectroscopy

The clamping effects on a passive direct methanol fuel cell (DMFC) performance have been analysed using electrochemical impedance spectroscopy (EIS). The stainless steel bolts of size M 6 × 0.75 mm with a length of 50 mm have been used for clamping the cell. The passive DMFC performance was conducted for different combinations of clamping bolt torque and methanol concentrations. It is found that the cell performance decreases with under and over uniform clamping bolt torque, and it is maximum at a particular clamping bolt torque. It is concluded from the EIS study that both the ohmic and mass transfer resistance decides the optimum clamping bolt torque of the passive DMFC. The EIS study also reveals that the non-uniform clamping bolt torque deteriorates the DMFC performance due to increase of the ohmic resistance and mass transfer resistance as well. The effects of bolt configurations on the cell performance have also been discussed. In this study, eight bolt configurations passive DMFC under 8.0 N m uniform clamping bolt torque produces optimum cell performance at 4 molar methanol concentrations. It is therefore recommended to decide clamping bolt torque accurately during assembling of the passive DMFC.