Insight into Proton Transfer in Phosphotungstic Acid Functionalized Mesoporous Silica-Based Proton Exchange Membrane Fuel Cells
MetadataShow full item record
We have developed for fuel cells a novel proton exchange membrane (PEM) using inorganic phosphotungstic acid (HPW) as proton carrier and mesoporous silica as matrix (HPW-meso-silica) . The proton conductivity measured by electrochemical impedance spectroscopy is 0.11 Scm-1 at 90 °C and 100% relative humidity (RH) with a low activation energy of ~14 kJ mol-1. In order to determine the energetics associated with proton migration within the HPW-meso-silica PEM and to determine the mechanism of proton hopping, we report density functional theory (DFT) calculations using the generalized gradient approximation (GGA). These DFT calculationsrevealed that the proton transfer process involves both intramolecular and intermolecular proton transfer pathways. When the adjacent HPWs are close (less than 17.0 Å apart), the calculated activation energy for intramolecular proton transfer within a HPW molecule is higher (29.1-18.8 kJ/mol) than the barrier for intermolecular proton transfer along the hydrogen bond. We find that the overall barrier for proton movement within the HPW-meso-silica membranes is determined by the intramolecular proton transfer pathway, which explains why the proton conductivity remains unchanged when the weight percentage of HPW on meso-silica is above 67 wt %. In contrast, the activation energy of proton transfer on a clean SiO2 (111) surface is computed to be as high as ~40 kJ mol-1, confirming the very low proton conductivity on clean silica surfaces observed experimentally.
Showing items related by title, author, creator and subject.
Phosphotungstic acid functionalized silica nanocomposites with tunable bicontinuous mesoporous structure and superior proton conductivity and stability for fuel cellsZeng, J.; Zhou, Y.; Li, L.; Jiang, San Ping (2011)A novel proton exchange membrane using phosphotungstic acid (HPW) as proton carrier and cubic bicontinuous Ia3d mesoporous silica (meso-silica) as framework material is successfully developed as proton exchange membranes ...
Anhydrous phosphoric acid functionalized sintered mesoporous silica nanocomposite proton exchange membranes for fuel cellsZeng, J.; He, B.; Lamb, K.; De Marco, Roland; Shen, P.; Jiang, San Ping (2013)A novel inorganic proton exchange membrane based on phosphoric acid (PA)-functionalized sintered mesoporous silica, PA-meso-silica, has been developed and investigated. After sintering at 650 °C, the meso-silica powder ...
Correlation between proton conductivity, thermal stability and structural symmetries in novel HPW-meso-silica nanocomposite membranes and their performance in direct methanol fuel cellsZeng, J.; Shen, P.; Lu, S.; Xiang, Y.; Li, L.; De Marco, Roland; Jiang, San Ping (2012)The intrinsic relationship between proton conductivity, thermal stability and structural symmetries of phosphotungstic acid (HPW)-functionalized mesoporous silica (HPW-meso-silica) membrane was investigated with mesoporous ...