Minimizing mass-transport loss in proton exchange membrane fuel cell by freeze-drying of catalyst layer

Kurzfassung

Polymer exchange membrane fuel cell (PEMFC) is considered a key alternative to internal combustion engine (ICE), which offers a clean chemical energy conversion at low operating temperature with a high power density and compact design. The reduction of Pt loading attracts special attentions to boost the commercialization of this technology. It involves constant investigation in the increment of activity, utilization and stability of the catalyst not only by the development of innovative catalyst formulations but also by the production of MEAs through cheap and easily-scalable coating and drying methods. Surprisingly, only few studies are present in the literature on the influence of drying techniques of the catalyst layer on performance of PEMFC. In fact, this final step affects significantly the electrode microstructure, associate with the porosity and the amount of reactive interphase. This work reports the use of freeze-drying technique that yields the unique feature of solvent removal via sublimation, from electrodes made of suspension coating. Here, we also compare the performance of cathode electrodes dried in three different techniques, which are oven drying, vacuum drying and freeze drying. Freeze dried electrode present 3.5-fold higher effective porosity, increased surface area and gas-diffusion pathways along with a homogenous distribution of ionomer surrounding the catalyst particles leading to higher reactive sites, Figure 1 a-b). The low Pt-loaded (0.160 mgPt∙cm-2) freeze dried electrode unveils better Pt utilization and higher power densities, Figure 1 c-d). This technique reveals a critical importance of consideration in the future MEA production.