~nerqy Week 2022
for Improved Water Management in PEFCs "Department of Automotive Selence: International Institute for Carbon-Neutrel Energy Research (20NER): Platform of Internetsdisciplinery Energy Research (CE2T) r  Introduction 🌸 Polymer Electrolyte Fuel Cells (PEFCs) are promising, highly efficient renewable energy technologies for next generation energy conversion devices.[1]۩Problem: Excessive water accumulation inside of the microporous layer and gas diffusion layer under the high current density operation conditions hinders oxygen transfer to the catalyst layer and decreases PEFC performance drastically.会Solution: To increase water removal speed with superhydrophobic fluorinated carbon (SHFC) as  MPL material.
Materials Synthesis
Fluorinated Alcohol Sodium Fluorinated Carbon By-product CF x HF + NaF etc Fig.2 Superhydrophobic fluorinated carbon’s synthesis procedures [2]۩  Sodium and fluorinated alcohol reacted in a sealed PTFE crucible at 150°  C for 24 hours. this食After reaction, the precursor is already carbonized by-products and are removed by washing it with a water and ethanol mixture. 🎁 The yield of the reaction was 20wt%.
Characterization
SEM reveals that the structure of SHFC is similar to carbon black.食BET specific surface analysis shows that SHFC has low surface area (40m²/g) compared to carbon black (100m²/g) Fig.5 Raman spectroscopy  analysis result TEM shows that SHFC contains気600 _400 500 700 800 200 300 900 1000 100 Temperature (C) high ordered graphitic structure. Fig.6  TG  analysis result 🎁 XRD analysis revealed sharp peaks at 25.9° and 26.5°, corresponding to fluorine dopped graphene and graphene formations respectively. and XRD 🎁 Raman results, spectroscopy analysis results support TEM and show that SHFC has multi layered graphene formation. 🎁 TG analysis results show that SHFC is stable until to 500° C under air.
Conclusions
息Superhydrophobic fluorinated carbon was synthesized at a low reaction temperature
高۩ The water contact angle measurement results showed that SHFC-based MPL has a contact angle higher than 150 °۩ The oxygen transport resistance tests and the single fuel cell performance test results signified that SHFC-based MPL has significantly higher performance at high current density operation conditions.
[2] Lyth S.M., Ma W., Liu J., Daio T., et al., Solvothermal synthesis of superhydrophobic  hollow nanoparticles from a fluorinated alcohol, Nanoscale, 2015, 7, 16087-16093 Diffusion [3] P.Wang, H.Nakajima, T. K. Hydrophilic and Hydrophobic Microporous Layer Coated Gas Layer for Enhancing PEFC Performance. ECS Trans. (2021). [4] Mashio, T., Ohma, A., Yamamoto, S. & Shinohara, K. Analysis of Reactant Gas in Transport Catalyst Layer. ECS Trans. 11, 529–540 (2019). a童Contact angle measurement shows that SHFC-based MPL’s water contact angle is higher than 150 °
Characterization
Air Permeance۩ Air permeabilities of CB-based and SHFC-based MPLs are measured at room conditions. Compared to SHFC-based MPLs, CB-based MPLs are more air permeable at low relative humidity conditions. Fig.9 Air permeability at room conditions [3] 🎁 Oxygen transport resistances at 45 ° C and 80 ° C with different high humidity conditions were measured.۩Opposite to the air permeability test, when relative humidity is high, at low and high cell temperatures, SHFC-based MPLs have lower oxygen transport resistance. results
References r
[1] Li, H. et al. A review of water flooding issues in the proton exchange membrane fuel cell. Power Fig.8 Surface contact angle measurement of SHFC and carbon black-based MPL with 5wt% PTFE loading.۩ Two different types of MPLs are coated on GDL: SHFC-based and CB-based.童To prepare MPLs, carbon material (SHFC or CB), methyl cellulose, deionized water, Triton-X and PTFE are mixed with a homogenizer. Then MPL slurry is coated on the GDL with a doctor blade. The final MPL thickness is 35 µm.۩ To sinter PTFE and decompose methyl cellulose and Triton-X, MPL coated GDLs are heat treated at 380 °  C. Humidity(%) Fig.10  Oxygen transport resistance [4]۩ Performance of SHFC-based MPL and CB-based MPL were compared with single fuel cell test results.۩The single fuel cell tests were conducted at 80 ゜C　cell temperature and high relative humidity conditions (80,100,120%).۩ The results are showing that when SHFC-based MPL employed in the cell, fuel cell  performance high all in increasing    dramatically relative humidity conditions. Fig.1a Schematic diagram of a PEFC
Characterization
Fig.1b Schematic illustration at the cathode side of PEFC under normal and high current density operation conditions. GDL Fig.7 Images of MPL coated (Na)