H3PO4 Loading Research Articles

A composite membrane of caesium salt of heteropolyacids/quaternary Diazabicyclo-octane polysulfone with poly (tetrafluoroethylene) for intermediate temperature fuel cells.

Inorganic-organic composite electrolyte membranes were fabricated from CsXH3−XPMo12O40 (CsPOMo) and quaternary diazabicyclo-octane polysulfone (QDPSU) using a polytetrafluoroethylene (PTFE) porous matrix for the application of intermediate temperature fuel cells. The CsPOMo/QDPSU/PTFE composite membrane was made proton conducting by using a relatively low phosphoric acid loading, which benefits the stability of the membrane conductivity and the mechanical strength. The casting method was used in order to build a thin and robust composite membrane. The resulting composite membrane films were characterised in terms of the elemental composition, membrane structure and morphology by EDX, FTIR and SEM. The proton conductivity of the membrane was 0.04 S cm−1 with a H3PO4 loading level of 1.8 PRU (amount of H3PO4 per repeat unit of polymer QDPSU). The fuel cell performance with the membrane gave a peak power density of 240 mW cm−2 at 150 °C and atmospheric pressure.

Membrane electrode assemblies doped with H3PO4 for high temperature proton exchange membrane fuel cells

H3PO4 content plays a critical role in high temperature proton exchange membrane fuel cells (HT-PEMFC), as it is responsible for the majority of the conductivity of the key components under high temperature operation. The conductivities of commercial AB-PBI membranes doped by immersing in 85 wt.% H3PO4 for different times and temperatures are investigated. The effect of H3PO4 loading in electrodes, including the AB-PBI polymer and a Pt/C catalyst, is also studied. The as-prepared electrodes and membranes are combined to fabricate a membrane electrode assembly for HT-PEMFCs. The results reveal that AB-PBI membranes doped with 85 wt.% H3PO4 at 90 °C for 9 h display a maximum conductivity of 33 mS cm−1. This membrane was selected and combined with electrodes including 15 wt.% AB-PBI and 0.75 mg cm−2 Pt with different H3PO4 loadings. A maximum current density of 260 mA cm−2 was achieved in the as-prepared MEA (with 5 mg cm−2 H3PO4 in electrodes) operating at 0.6 V and 160 °C, using oxygen and hydrogen.

H3PO4-imbibed three-dimensional polyacrylamide/polyacrylamide hydrogel as a high-temperature proton exchange membrane with excellent acid retention

We herein report the use of polyacrylamide/polyacrylamide interpenetrating polymer network (PAM/PAM IPN) hydrogel as a matrix to imbibe proton conducting H3PO4, forming a robust proton exchange membrane (PEM) suitable for high-temperature PEM fuel cells by combining excellent acid retention, simple synthesis, and low cost. Its extraordinary ability to absorb large quantity of aqueous solution is fully utilized to achieve high H3PO4 loading, showing a proton conductivity of 0.0833 S cm−1 at 183 °C in dry air. The synthesized membrane also shows excellent acid retention even under mechanical load and high humidity. These profound advantages along with simple and low-cost synthesis promise the new membrane to be a strong candidate as a high-temperature PEM.

A PBI‐Sb0.2Sn0.8P2O7‐H3PO4 Composite Membrane for Intermediate Temperature Fuel Cells

AbstractFine particles of a solid proton conductor Sb0.2Sn0.8P2O7 were incorporated in PBI‐H3PO4 membranes with 20 wt.%. In SEM figures, the Sb0.2Sn0.8P2O7 particles exhibited even and uniform distribution in the PBI‐Sb0.2Sn0.8P2O7 membrane. Influences of the immersing time and the concentration of H3PO4 solution for immersion on H3PO4 loading level were investigated. H3PO4 loading level was found an important factor on membrane conductivity. Incorporation of Sb0.2Sn0.8P2O7 in the PBI‐H3PO4 membrane resulted in greater membrane conductivities. In the single cell tests, the peak power density of the membrane electrode assembly (MEA) with the PBI‐Sb0.2Sn0.8P2O7‐H3PO4 membrane was also greater than that of a MEA with PBI‐H3PO4 membrane. One MEA using PBI‐Sb0.2Sn0.8P2O7‐H3PO4 membrane achieved a peak power density of 0.67 W cm–2 at 175 °C with H2/O2 and exhibited satisfactory stability.

Precise determination of Sm, Nd concentrations and Nd isotopic compositions at the nanogram level in geological samples by thermal ionization mass spectrometry

In this paper, a high sensitivity method for measurements of Nd isotopes as NdO+, on a TIMS using a single W filament with TaF5 as an ion emitter is presented. Although analyzing Nd isotopes as oxides (NdO+) is a well known technique, this is the first report to analyze Nd isotopic compositions as oxides using W filaments and the TaF5 emitter. When 0.5–1 ng loads of a Neodymium isotopic reference reagent, JNdi-1, were measured using this method, the ion yields were found to be mostly in excess of 15% and could be as high as 32%. Internal precision on 143Nd/144Nd could be better than 10 ppm (2SE) for 1 ng JNdi-1 loads and better than 15 ppm (2SE) for 0.5 ng JNdi-1 loads; thirteen replicates of 0.5–1 ng JNdi-1 loads yielded a 143Nd/144Nd value of 0.512112 ± 0.000028 (2SD). Compared with the previously reported NdO+ measurement method using the Re (or W) filaments + Silica-gel + H3PO4 loading techniques, this method has advantages including higher sensitivity, a more stable ion beam, and no need for oxygen gas to be bled into the ion source chamber. Sm isotopes were analyzed as Sm+ using the W filaments and the TaF5 emitter, and high sensitivity and good ion beam stability were also obtained. Several international rock reference materials, including an ultramafic rock reference material USGS PCC-1 that contains very low amounts of Sm and Nd, were analyzed with full column chemistry and the TaF5 method, and the results of Sm, Nd concentrations and Nd isotopic data are in good agreement with the reported values. Combined with a highly efficient and low-blank column chemistry to separate Nd from Sm, Ce, and Pr, this method holds potential to analyze Sm, Nd concentrations and Nd isotopic compositions of highly depleted peridotites; very small aliquots of minerals such as garnets; extra-terrestrial materials of limited sample size; and environmental samples that contain very low quantities of Sm and Nd.

Structure and reactivity of phosphorous modified H-ZSM-5 catalysts for ethanol dehydration

Abstract H3PO4/H-ZSM-5 catalysts were prepared by impregnation method with varying H3PO4 loadings from 5 to 20 wt%. The H3PO4 modified catalysts were found to be highly active and selective towards ethylene during ethanol dehydration at 673 K. However, the selectivity was found to strongly depend on the content of H3PO4, reaction temperature and WHSV. The catalysts were characterized using X-ray diffraction, NH3-TPD, N2 physisorption, 27Al, and 31P MAS NMR techniques.

Alumina/Epoxy Interpenetrating Phase Composite Coatings: I, Processing and Microstructural Development

Interpenetrating phase composite (IPC) coatings consisting of continuously connected Al2O3 and epoxy phases were fabricated. The ceramic phase was prepared by depositing an aqueous dispersion of Al2O3 (0.3 μm) containing orthophosphoric acid, H3PO4, (1–9.6 wt%, solid basis) and heating to create phosphate bonds between particles. The resulting ceramic coating was porous, which allowed the infiltration and curing of a second‐phase epoxy resin. The effect of dispersion composition and thermal processing conditions on the phosphate bonding and ceramic microstructure was investigated. Reaction between Al2O3 and H3PO4 generated an aluminum phosphate layer on particle surfaces and between particles; this bonding phase was initially amorphous, but partially crystallized upon heating to 500°C. Flexural modulus measurements verified the formation of bonds between particles. The coating porosity (and hence epoxy content in the final IPC coating) decreased from ∼50% to 30% with increased H3PO4 loading. The addition of aluminum chloride, AlCl3, enhanced bonding at low temperatures but did not change the porosity. Diffuse reflectance FTIR showed that a combination of UV and thermal curing steps was necessary for complete curing of the infiltrated epoxy phase. Al2O3/epoxy IPC coatings prepared by this method can range in thickness from 1 to 100 μm and have potential applications in wear resistance.