Abstract
The stacking and overlapping effect of two-dimensional (2D) graphene nanosheets in the catalyst coating layer is a big challenge for their practical application in proton exchange membrane fuel cells (PEMFCs). These effects hinder the effective transfer of reactant gases to reach the active catalytic sites on catalysts supported on the graphene surface and the removal of the produced water, finally leading to large mass transfer resistances in practical electrodes and poor power performance. In this work, we evaluate the catalytic power performance of aligned Pt nanowires grown on reduced graphene oxide (rGO) (PtNW/rGO) as cathodes in 16-cm2 single PEMFCs. The results are compared to Pt nanoparticles deposited on rGO (Pt/rGO) and commercial Pt/C nanoparticle catalysts. It is found that the scaffolding effect from the aligned Pt nanowire structure reduces the mass transfer resistance in rGO-based catalyst electrodes, and a nearly double power performance is achieved as compared with the Pt/rGO electrodes. However, although a higher mass activity was observed for PtNW/rGO in membrane electrode assembly (MEA) measurement, the power performance obtained at a large current density region is still lower than the Pt/C in PEMFCs because of the stacking effect of rGO.
Highlights
With the commercial release of the Toyota Mirai and Hyundai ix35 fuel cell vehicles, the viability of using proton-exchange membrane fuel cells (PEMFCs) as the power source in transport applications has been demonstrated
We evaluated the catalyst electrodes made from Pt(NW)Pd/reduced graphene oxide (rGO) and Pt nanoparticles deposited on rGO (Pt/rGO) in PEMFCs and the results were compared to Pt/C nanoparticle catalysts
The results demonstrated that the introduction of rGO-based catalysts tended to form a dense structure within the catalyst layer that limited the mass transfer in fuel cell operation and resulted in poor power performance
Summary
With the commercial release of the Toyota Mirai and Hyundai ix fuel cell vehicles, the viability of using proton-exchange membrane fuel cells (PEMFCs) as the power source in transport applications has been demonstrated. For the widespread adoption of such vehicles, larger power outputs and long-term durability are required at a reduced cost [1,2]. Platinum group metals (PGM), and platinum (Pt), are inherently the most active catalysts towards the ORR [3] as well as the most stable in the acidic conditions of the PEMFC. Due to their high cost and low performance compared to theoretical values, much effort has been directed to developing novel methods of reducing the PGM content while increasing the catalytic activity [4]. Sun et al synthesized Pt nanowires supported on carbon black (PtNW/C) by the simple wet chemical route of using formic acid to reduce chloroplatinic acid to
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