The development of next generation fuel cell membranes based on aromatic hydrocarbon chemistry calls for a new antioxidant strategy to tackle radical induced membrane degradation. Although damage by radicals cannot be prevented, the formed aromatic intermediates can be repaired by a suitable additive. Fuel cell experiments demonstrate that the approach is viable on the device level and that repair is a catalytic mechanism.
Water management is crucial to the successful cold-start in polymer electrolyte fuel cells (PEFCs). The sudden freeze of supercooled water blocks the reactant gas in the cathode and causes rapid voltage failure. In this work, we statistically evaluated the effects of the gas diffusion layer (GDL) substrate, size, saturation, and the coating loads and methods of hydrophobic polymer on the freezing probability of supercooled water by differential scanning calorimetry (DSC).
Hydrogen will play an important role in a future energy system based on renewable sources, providing energy storage, being a base material for industry and an energy carrier in transport applications. For the efficient electrification of hydrogen, polymer electrolyte fuel cell technology is developed and applied today in trucks, passenger cars and stationary applications. It is envisaged that even more demanding applications such as airplanes may follow. For road transport applications an increase in power density is required to further reduce cost and future applications may need these advances to be technically competitive. In this work we describe a novel concept for gas diffusion layers, highly important for achieving high fuel cell power densities.
High performance doped Li-rich Li1+xMn2-xO4 cathodes nanoparticles synthesized by facile, fast and efficient microwave-assisted hydrothermal route
Li-rich nanoparticles of Li1+xMn2-xO4 doped with Al, Co or Ni are successfully synthesized using a facile, fast and efficient microwave-assisted hydrothermal route. In this study, we demonstrate that nanocrystallinity and cationic doping play an important role in improving the electrochemical performance with respect to LiMn2O4 microparticles. They significantly reduce the charge-transfer resistance, lower the 1st cycle irreversible capacity to 6%, and achieve a capacity retention between 85 and 90% after 380 cycles, with excellent columbic efficiency close to 99%.
Lithium-rich layered oxides, containing cobalt, despite being promising high-capacity cathode materials, need alternatives to eliminate toxic and geopolitically restricted cobalt. An ongoing search for low-cost, Co-free Li-rich cathode materials with a better structural stability lead to investigation of Li1.16Ni0.19Fe0.18Mn0.46O2 (LNFM), where cobalt is replaced by abundant iron. Our LNFM not only delivered a high capacity of 229 mAh/g but also has a stable average discharge voltage when cycled to upper cutoff potential of 4.8 V in additive-free electrolyte.
To improve the performance of single atom catalysts (SACs), the structure of their active sites under operative conditions needs to be better understood. For this, we have performed in situ X-ray absorption spectroscopy measurements using a modulation excitation approach selectively sensitive to the species involved in the electrochemical reactions. This has allowed us to study the structural changes undergone by two types of SACs, and to tie the observed differences to their catalytic activities.
The conversion efficiency for green hydrogen production in a polymer electrolyte water electrolyzer (PEWE) is strongly influenced by the ohmic cell resistance and therefore the thickness of the membrane used. The use of thin membranes (~50 micron or below) is limited by gas crossover of H2 and O2, which can lead to the formation of explosive gas mixtures. The incorporation of a recombination catalyst provides remedy and allows a more dynamic operating mode.
Understanding the water management in polymer electrolyte fuel cells (PEFCs) during sub-zero operation is crucial for designing effective freeze start strategies. In collaboration with Toyota Motor Europe sub-second X-ray tomographic microscopy was used to study the water distributions in the gas diffusion layer (GDL) of PEFCs during dynamic freeze starts from −30 °C that mimic automotive freeze start conditions at different pre-drying levels and varying the feed gas humidity.
Direct evidence of in situ Co-oxyhydroxide formation on the surface of La0.2Sr0.8CoO3-δ water splitting catalyst
We carried out in situ and ex situ ambient pressure X-ray photoelectron spectroscopy (APXPS) experiments on a La0.2Sr0.8CoO3-δ perovskite oxygen evolution reaction (OER) catalyst. The study shows that Sr is leached into the electrolyte after immersion, leading to surface Co active site enrichment. Such a Co-enriched surface evolves into a new phase during operation. With the help of theoretical simulations, such a species is assigned to Co-oxyhydroxide, providing direct evidence of its formation during the OER.