Effect of tunable hydrophobic level in the gas diffusion substrate and microporous layer on anion exchange membrane fuel cells

The anion exchange membrane fuel cell, based on hydroxide conduction, has been paid much attention recently due to its strength of improved cathode performance, non-precious metal catalysts, and low-cost electrolyte. However, its electrochemical reaction simultaneously involving in the production/consumption of water at anode/cathode makes it difficult to maintain an optimized hydration of anion exchange membrane and the electrodes, thereby limiting the attainable cell performance. Accordingly, reaching a sophisticated water management is urgently required. Herein, we systemically investigate the hydrophobic effect of gas diffusion substrate, strongly affecting the water condition, on the anion exchange membrane fuel cell. A series of gas diffusion substrates with different hydrophobic level are designed by controlling amount of polytetrafluoroethylene within gas diffusion substrates and with/without microporous layer atop to evaluate single cell performance. Our result shows that a good device performance can be obtained by using the gas diffusion substrate with higher polytetrafluoroethylene loadings and microporous layer both at anode and cathode. It can be mainly attributed to the multifunction of polytetrafluoroethylene in gas diffusion substrate, offering the advantages of the appropriate hydrophobic control and robust supporting for the microporous layer and catalyst layer to achieve a sophisticated water control during the operation.