Novel bimetallic Pt/Ru catalysts for efficient direct methanol fuel cell

Abstract

In recent years, with the pursuit of more sustainable development, direct methanol fuel cells (DMFCs) have become an attractive energy conversion device option. DMFCs have unique advantages, such as high energy conversion efficiency, more convenient storage and transportation of liquid fuels, and low operating temperature. However, they still face some problems in enabling broad adaptation. One critical issue is the lack of efficient and stable electrocatalysts for methanol oxidation reaction (MOR) with good resistance to contaminants generated during MOR. Among various potential catalyst candidates, PtRu bimetallic nanoparticles supported on carbon substrates (PtRu/C) have emerged as a front runner, acclaimed for their high catalytic activity, lower cost, and resistance against CO poisoning. However, obtaining PtRu bimetallic nanoparticles with uniform size distributions is still challenging. This thesis reports a new approach to synthesizing PtRu/C catalysts via a Joule heating method. The optimization of synthesis conditions from 850 to 1150 °C and 30 to 500 ms shows that uniform PtRu nanoparticles supported on carbon black (6.32 wt.% Pt and 2.97 wt.% Ru) with an average size of 2.0 ± 0.5 nm have been produced at 1000 oC over 50 ms. They have a large electrochemically active surface area (ECSA) of 239 m2 g–1, and a high ECSA normalized specific activity of 0.295 mA cm–2. They demonstrate a peak mass activity of 705.9 mA mgPt–1 for MOR, 2.8 times that of a commercial 20 wt% Pt/C catalyst, and much superior to PtRu catalysts obtained by the standard hydrothermal synthesis method. It also shows excellent stability in two-electrode methanol fuel cell tests with 85.3% current density retention with minimum Pt surface oxidation after 24 hours. Scalable Joule heating-based catalyst production techniques may be developed to produce high-performance catalysts if precise heating condition controls are achieved.