Engineering catalyst layers for next-generation polymer electrolyte fuel cells: A review of design, materials, and methods. Designing the next generation of proton-exchange membrane fuel cells. Finally, it is found that the loss of carbon and PTFE in GDLs lead to a higher hydrophilicity, which is related to an occurrence of water flooding and increase in the oxygen transport resistance. Both cation contamination and chemical decomposition will change the structure of ionomer, thus worsening the local oxygen transport. It is also noted that problems concerning oxygen transport caused by the degradation of ionomer chemical structure in CCLs should not be ignored. Considering the catalyst degradation, an eventual decrease in electrochemical active surface area (ECSA) definitely increases the local oxygen transport resistance since a decrease in active sites will lead to a longer oxygen transport path. It is analyzed that carbon corrosion in CCLs will result in pore structure destruction and impact ionomer distribution, thus affecting both the bulk and local oxygen transport behavior. In this review, influences of the degradation of key materials in membrane electrode assemblies (MEAs) on oxygen transport resistance in both cathode catalyst layers (CCLs) and gas diffusion layers (GDLs) are comprehensively explored, including carbon support, electrocatalyst, ionomer in CCLs as well as carbon material and hydrophobic polytetrafluoroethylene (PTFE) in GDLs. However, compared to effects of material degradation on apparent activity loss, little attention has been paid to influences on the phenomena of mass transport. One very famous example was in 1922 when archaeologist Howard Carter discovered the tomb of King Tutankhamen, a pharaoh who died when he was only nineteen.A large-scale industrial application of proton exchange membrane fuel cells (PEMFCs) greatly depends on both substantial cost reduction and continuous durability enhancement. Explorers and archaeologists have discovered these tombs and learned a great deal about ancient Egyptian society from them. Hatshepsut, in particular, was a successful ruler, but many inscriptions and monuments about her were destroyed after her death-perhaps to stop future women from becoming pharaohs.Īfter their deaths, many pharaohs were entombed and surrounded by riches they were meant to use in the afterlife. Pharaohs were typically male, although there were some noteworthy female leaders, like Hatshepsut and Cleopatra. Though there is some debate among experts, many believe he was the first ruler to unite upper and lower Egypt (this is why pharaohs hold the title of “lord of two lands”). Many scholars believe the first pharaoh was Narmer, also called Menes.
As a statesman, the pharaoh made laws, waged war, collected taxes, and oversaw all the land in Egypt (which was owned by the pharaoh).
Maintaining religious harmony and participating in ceremonies were part of the pharaoh’s role as head of the religion.
While early Egyptian rulers were called “kings,” over time, the name “pharaoh” stuck.Īs the religious leader of the Egyptians, the pharaoh was considered the divine intermediary between the gods and Egyptians. The word “pharaoh” means “Great House,” a reference to the palace where the pharaoh resides. As ancient Egyptian rulers, pharaohs were both the heads of state and the religious leaders of their people.
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