Investigation of a Silicotungstic Acid Functionalized Carbon on Pt Activity and Durability for the Oxygen Reduction Reaction

Abstract

Colloidal Pt prepared by an ethylene glycol reduction method was deposited onto Ketjen black carbon supports functionalized with (0, 3.2, 7.1, and 15.9wt%) 11-silicotungstic acid (Pt/SiW 11 -C). Electrochemical characterization of the catalysts was performed using rotating disk electrodes (RDE) in 0.1 M HClO 4 electrolyte. XRD and TEM showed smaller crystallite size and more uniform deposition of Pt nanoparticles for Pt/SiW 11 -C catalysts, respectively. A maximum in the ORR mass activity of 373 mA/mg Pt was observed for the 3.2wt% SiW 11 catalyst, an 18% improvement over Pt/C. An increase in the electrochemical area (ECA) due to lower Pt particle size and more narrow size distribution is attributed to providing the mass activity enhancement. After 30,000 durability cycles in the potential range 0.6-1.0 V, Pt/SiW 11 -C showed less Pt particle growth (TEM), and a factor of 1.4 improvement in terms of mass activity retention. After 6,000 durability cycles in the potential range 1.0-1.6 V, Pt/SiW 11 -C showed a factor of 2 increase in mass activity retention compared to Pt/C. The improvement is attributed to a slower rate of carbon corrosion.

Performance of Silicotungstic Acid Modified Platinum Cathodes at High Temperature and Low Relative Humidity for PEMFCs

“…Wlodarczyk et al concluded that for the operating conditions for oxygen reduction all heteropolyacids should remain stable on platinum and carbon. 27 durability on carbon following 6000 cycles between 1.0 and 1.6 V. 40 Degradation testing is used to simulate life-time testing and evaluate the PEMFC components and performance parameters over a short period of time. During extended cell testing at 120 • C/35% RH and during degradation testing electronic shorts were observed in some cells as seen in Fig.…”

“…Mason et al showed an increase in ECSA on functionalized carbon with SiWA loadings up to 7.1% and then a decrease at higher loadings. 40 Polarization curves were obtained for cells containing 3, 6, 15% SiWA using the blend fabrication, 16% SiWA for the soak fabrication, 15% SiWA using the pH modified fabrication and 0.5 and 2.5 M SiWA dip fabrication to evaluate performance against the established baseline. Data were collected at 80 • C/100% RH on H 2 /air and H 2 /O 2 .…”

“…Mason et al showed an increase in ECSA on functionalized carbon with SiWA loadings up to 7.1% and then a decrease at higher loadings. 40 Polarization curves were obtained for cells containing 3, 6, 15% SiWA using the blend fabrication, 16% SiWA for the soak fabrication, 15% SiWA using the pH modified fabrication and 0.5 and 2.5 Comparison of ECSA measurements for electrodes using the four fabrication techniques with SiWA compared to electrodes with no SiWA. ECSA of the TEC10E50E catalyst powder: 132 m 2 /g Pt.…”

Performance of H2-fed fuel cell with chitosan/silicotungstic acid membrane as proton conductor

“…In fact, according to the literature, hybrid polymer-silicotungstic acid (STA) membranes have a high thermal stability, promising mechanical strength and proton conductivity [10,[15][16][17][18]. Moreover, the addition of STA to the electrodes of polymer electrolyte membranes fuel cells is reported to enhance the activity of platinum towards oxygen reduction reaction and the stability of the membrane [19][20][21].…”

Chemical Stability via Radical Decomposition Using Silicotungstic Acid Moieties for Polymer Electrolyte Fuel Cells

“…19,20 A method of covalent bonding HPAs to carbon in the catalyst layer has also shown some improvements in chemical stability, but chemical degradation mitigation within the membrane is needed. 21,22 Our group has developed two membrane platforms with HPAs covalently attached and immobilized within a polymer membrane, serving as the proton conducting acid. [23][24][25][26] More recently, the outstanding chemical stability of one of these platforms has been demonstrated, 26 however, the stability demonstrated in this study was criticized for using rather thick, 80 μm membranes in subscale fuel cells.…”