Fabrication of nano-network structure anode by zinc oxide nanorods template for passive direct methanol fuel cells

Abstract

In this study, zinc oxide (ZnO) nanorods were used as efficient sacrificial template to fabricate nano-network structure (NNS) within anode catalyst layer (CL) and micro-porous layer (MPL) of a membrane electrode assembly (MEA). It resulted in a significant reduction of noble metal catalyst loading and enhancement of performance of a passive direct methanol fuel cell (DMFC). At a Pt–Ru loading of 1.0 mg cm−2, the MEA with NNS in anode CL exhibited a maximal power density of 28.4 mW cm−2 using 2 M methanol solution as fuel at 25 °C. However, for the conventional MEA with a Pt–Ru loading of 2.0 mg cm−2, the maximal power density was 29.0 mW cm−2. With the increase in Pt–Ru loading to 2.0 mg cm−2, the maximal power densities of the MEAs with NNS in anode CL and in both anode CL and MPL reached 38.6 and 40.2 mW cm−2, respectively. The improved performance of the MEAs with NNS was attributed to its property of higher catalyst utilization, higher mass transfer efficiency, and lower charge-transfer resistance compared to the conventional MEAs. However, the construction of NNS within both anode CL and MPL led to a relatively serious problem of cathode flooding, which restrained the further improvement in DMFC's performance. This study provided a perspective to fabricate novel pore structure to obtain high performance of passive DMFCs with low noble metal catalyst loading and low concentration methanol solution.