Redox Shuttle To Improve MEA Durability

Membrane Electrode Assembly (MEA), as the key component of Proton Exchange Membrane Fuel Cell (PEMFC), mainly consists of proton exchange membrane (PEM), Gas Diffusion Layer (GDL) and catalyst layers (CL). Especially, the catalyst layer acting as the center for electrochemical reaction in PEMFC facilitates reactant transport, interface reaction in electrochemical active site and conduction of proton and electron. In working condition, because of PEMFC frequent start-up and shut-down, load changes, humidity changes, causing abnormal distribution of electric potential inside the battery, resulting in anode and cathode catalyst layer produced localized corrosion, lead to the Fuel Cells performance degradation. In this thesis, overcharge protection potential clamp mechanism ever used in lithium-ion battery was applied to fuel cells to mitigate or even diminish the corrosion caused by the high potential. The potential clamping was realized by the implantation of the redox shuttle into the MEA.By electrochemical and other physical methods, suitable redox shuttles were investigated. Experimental results and main conclusions are as follows:(1) Clamping the cathode to a suitable potential and then improving the durability of fuel cell by the implantation of redox shuttle was firstly proposed.(2) Redox shuttle with suitable clamping potential and reversibility were obtained, such as o-toluidine,3,3,-Dimethoxybenzidine, N, N-dimethylaniline.(3) O-toluidine with a equlibrium potential of 0.58V (vs.SCE), shows good electrochemical reversibility and chemical stability. Single-cell test results indicate that the o-toluidine can effectively inhabit the high voltage and consequently improve the durability of PEMFC.(4) 3,3,-Dimethoxybenzidine with a equilibrium potential of 0.6V (vs.SCE), exhibits good electrochemical reversibility and chemical stability. Although 3,3,-Dimethoxybenzidine can clamp the potential at a suitable value, it impose negative effect on the fuel cell systems.