In the last few decades, a variety of nanomaterials with controlled size, shape, composition, and morphology have been developed with wet chemistry synthesis methods which show much improved catalytic activity improvements for oxygen reduction reaction (ORR) in rotating disk electrode (RDE) testing compared with commercial Pt/C catalyst. However, their performance in membrane electrode assembly (MEA) was rarely investigated. The main challenge is the difficulty to transfer lab scale batch synthesis to large scale high quality catalyst preparation. With multilayered Pt-skin nanoparticle catalyst as an example, here we show the scale up synthesis of advanced fuel cell catalyst. By modifying three key steps of the synthesis procedure, a process capable of producing 5 g catalyst per batch with higher performance reproducibly is developed. Compared with commercial Pt/C catalyst, the scaled up catalysts show 10-fold activity improvements toward ORR in RDE measurements. Pt mass activity of 0.5 A/mg at 0.9 V has been achieved in 50 cm2 MEA measurement, which is higher than DOE 2020 target. Significant lower non-Fickian oxygen transport resistance than commercial catalyst is observed in MEA testing which is ascribed to higher accessibility of the multilayered Pt-skin nanoparticle catalyst. Revealed by TEM tomography, all the catalytic particles are located on the surface of carbon indicating the superiority of the synthesis method in controlling the location of the catalytic nanoparticles than commercial impregnation method. Aiming to accelerate transition of advanced nanomaterials from discovery lab to manufacturing, we establish a flow reactor based nanomaterial scale up platform. We show the successful synthesis of PtNi nanoparticles in continuous flow reactor and demonstrate unchanged particle size and composition with more than two hours of operation. Compared with the catalyst prepared with batch synthesis, the catalyst produced in continuous flow reactor shows higher ORR activity in RDE testing, indicating high quality particle synthesis. The particle size, morphology, and composition changes with function of reaction conditions are also investigated. Combined with in-situ measurements at Advanced Photon Source at Argonne National Laboratory, we show the possibility of accelerating nanomaterials scale up with science based flow reactor platform.

Scale up of advanced fuel cell catalysts in batch and flow reactors

2019 Fall National Meeting

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