Laser Structured Gas Diffusion Layers for Improved Water Transport and Fuel Cell Performance
Christoph Csoklich, Hong Xu, Federica Marone, Thomas J. Schmidt, Félix N. Büchi
Abstract
Polymer electrolyte fuel cells are promising energy converters for future green energy systems. For wide commercial use, still cost reductions by increasing the power density are required. Structurally optimized gas diffusion layers (GDLs), allowing for cell operation at high current densities with reduced mass transport losses, are an essential component for this development. Here we demonstrate that GDLs modified with perforations can improve water transport in the high current density regions and increase fuel cell performance. Laser perforation prior to GDL hydrophobization circumvents previously observed flooding problems and allows for stable operation. The advanced pattern, connecting channel and land regions drains pores, hence decreasing the liquid water fraction, especially close to the GDL and catalyst layer interface. Operando dynamic X-ray tomographic microscopy (XTM) is employed to understand water transport in the modified structure, and the competition with random break-through of water clusters to the channel is analyzed. The detailed and time-resolved insights allow us to propose guidelines for future advanced patterning geometries, suggesting denser perforations and methods to counteract the observed high frequency resistance (HFR) increase. Furthermore, this approach can act as model system for next generation GDLs and lead to a more rational design of transport layers.