The durability of polyol-synthesized PtRu/C for direct methanol fuel cells

The durability of polyol-synthesized PtRu/C as anode electrocatalyst for direct methanol fuel cells (DMFCs) has been studied by conducting a 2020-h life-test of a single cell discharging at a constant current density of 100 mA cm⁻². Critical fuel cell performance parameters including anode activity, cathode activity and internal resistance are, for the first time, systematically examined at the life-test time of 556, 1093, 1630 and 2020 h. High-resolution transmission electron microscopy and X-ray diffraction (XRD) have also been performed and show that PtRu nanoparticles have agglomerated with the mean particle size increasing from 1.82 to 2.78 nm after the 2020-h life-test. Anode polarization and electrochemical impedance spectroscopy (EIS) show that there exists a stable discharging period where the anode polarization potential is less than 0.363 V versus dynamic hydrogen electrode (DHE). When the anode polarization potential exceeds 0.363 V versus DHE, the performance of the anode degrades dramatically due to the leaching of the unalloyed Ru as indicated by energy dispersive X-ray spectroscopy (EDS) and XRD. This finding provides clues in developing strategies to operate fuel cells achieving maximum lifetime without noticeable performance lose.