Enhancing Cell Performance and Durability of High Temperature Polymer Electrolyte Membrane Fuel Cells by Inhibiting the Formation of Cracks in Catalyst Layers

Abstract

Cracks in catalyst layers (CLs) serve as gateway for phosphoric acid (PA) leaching. It significantly affects the performance and durability of high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Thus it is an important issue to control the cracks formation in CLs. Herein, a simple and effective way has been developed to minimize cracks via introducing carbon nanotubes (CNTs) into CLs. The effects of CNTs on performance and durability of HT-PEMFC have been evaluated. The introduction of CNTs reinforces the structure of CLs with small cracks. It also regulates pore structure of cathode CLs with reduced PA invading and enhancement of mass transfer. The CNTs addition also enhances oxygen reduction reaction kinetics confirmed by the test of half-cell setup. With addition of 2.0 wt% CNTs in the cathode CL, the peak power density of HT-PEMFC is 673 mW cm−2 at H2/O2 and 160 °C, which is 1.5 times higher than that of the cell without CNT in the cathode CL. More importantly, at high current density of 1.5 A cm−2 and frequent restarts, the HT-PEMFC based on the optimized electrode still keeps better stability compared to the control electrode due to weakened impact of PA flooding. Furthermore, the cell shows slight voltage decay for 900 h of durability test with a constant current load of 0.2 A cm−2 under a constant stoichiometry ratio (λH2: λAir= 1.2:2.5).