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A hydrogen‐based energy system will be the backbone of a future energy grid using renewable energies. It is widely accepted that polymer electrolyte membrane fuel cells (PEMFCs) are promising converters of chemical energy stored as hydrogen into electrical energy. An increase of the operation temperature from below 80°C to above about 160°C is considered beneficial, as it would allow for much simpler water management and the use of waste heat. Here, we are investigating protic ionic liquids (PILs) immobilized in a polybenzimidazole polymer as electrolytes for high‐temperature PEMFCs. Ionic liquids are promising for fuel cell applications as they provide high thermal and chemical stability and high proton conductivity. In contrast to aqueous electrolytes, ionic liquids form a dense layered structure at the electrode–electrolyte interface that depends on the potential and on the content of residual water in the electrolyte. We investigate how PILs interact with the host polymer of the membrane revealing that porous polymer structures can be formed by solution casting, which allows for an encapsulation of the ionic liquid within the pores. After doping the polymer with small amounts of phosphoric acid, the membranes showed reasonable conductivity and fuel cell performance. [ABSTRACT FROM AUTHOR]

This paper investigates the general performance and durability performance of a high-temperature polymer electrolyte fuel cell (HT-PEFC) with CrN/Cr-coated SS316L as bipolar plates and compares this with the bare SS316L and graphite bipolar plates. Polarization curves are conducted every 200 h during the 1000 h durability tests for evaluating the overall performances of the HTPEFCs with different types of bipolar plates. An electrochemical model based on polarization curves, combined with electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM), is used for understanding the degradation mechanisms at play. The CrN/Cr-coated SS316L bipolar plates show excellent corrosion resistance and performance in a real HTPEFC. Thereby, the degradation rate decrease from ca. 16% of the highest output power with the bare metallic bipolar plates and graphite bipolar plates to almost zero with the CrN/Cr-coated steel bipolar plate. [ABSTRACT FROM AUTHOR]

Increasing attention is being paid to the use of metallic materials as a replacement for non-porous graphite in the bipolar plates of polymer membrane fuel cells, including high-temperature polymer membrane fuel cells (HT-PEFCs). This work investigates the corrosion and electrical properties of SS316L stainless steel in the simulated anode and cathode environments of HT-PEFCs. The influence of gases on the free corrosion potential (Ecorr), free corrosion current (icorr) and dynamic formation of passive layers were analyzed in 85 wt% phosphoric acid at RT and 130°C by means of potentiodynamic and potentiostatic tests, together with open circuit potential (OCP) measurements. The working potential of the anode (0.05V) is located in the active corrosion region, while the working potential of the cathode (0.65V) is located in the passive corrosion region. The potentiostatic tests show that the corrosion rate of SS316L in the simulated anode environment of an HT-PEFC is 10 times higher than that in the simulated cathode environment of an HT-PEFC. The free corrosion potentials, immediately noted after potentiostatic tests, show that the existence of oxygen could improve the stability of the passive layer formed during the potentiostatic stage. Scanning electron microscopy (SEM) results showed different morphologies of the corroded surface. Inductively-coupled plasma optical emission spectrometry (ICP-OES) and interfacial contact resistance (ICR) was then used to determine the levels of metal ions in the solution after corrosion and the influence of the passive layer on the ICR of metallic bipolar-plates separately made from SS316L. X-ray photoelectron spectroscopy (XPS) was used to investigate the distribution of elements on the surface of samples before and after the corrosion tests. These ex-situ measurements showed that in the anode environment, SS316L undergoes active corrosion, which results in a higher level of leaching metal ions and lower value of ICR compared to that in a cathode environment, which has a passive corrosion environment. The specimen in the cathode environment showed lower values of ICR and the number of leaching metal ions when exposed to oxygen compared with the nitrogen atmosphere. The passive layer formed in a simulated cathode environment with an oxygen purge shows the best corrosion resistance within hot phosphoric acid. The XPS results indicate that this is a Cr-rich layer. The thickness of the surface films was estimated to range from 1.1-2.2 nm. [ABSTRACT FROM AUTHOR]