Table 7.
Functionalization method of SiO2 via different reagents, and representative PEM properties of corresponding composite membranes.
| Sample (Matrix/Filler) |
Filler Content (wt. %) |
Functionalization of SiO2 | Water Uptake a (%) |
IEC b (meq g−1) |
Proton Conductivity c (mS cm−1) | Ref. | ||
|---|---|---|---|---|---|---|---|---|
| Agent | Method | 20% RH | 80% RH | |||||
| Nafion/SiO2 | 2.0 | - | - | 35.6 | - | 7.5 | 80.0 | [134] |
| Nafion/Silica sulfonic acid | - | Chlorosulfonic acid | Sulfonation | 32.2 | 1.5 | 40.0 | 175 | [128] |
| Nafion/SSA d | 1.0 | TEOS, Chlorosulfonic acid | In situ sol-gel methods | 24.1 | 1.3 | 8.8 | 230 (100% RH) |
[122] |
| SPAES/SiO2 | 5.0 | - | - | 36.7 | 1.7 | 1.0 (40% RH) |
102 (90% RH) |
[126] |
| SPAES/S-Si e | 5.0 | 4-styrensulfonic acid sodium salt hydrate |
Radical polymerization | 40.9 | 1.7 | 1.3 (40% RH) |
140 (90% RH) |
[126] |
| SPAES/P-Si f | 5.0 | 4-vinylpyridine | Radical polymerization | 34.3 | 1.6 | 2.3 (40% RH) |
146 (90% RH) |
[126] |
| SPPSU/SM-SiO2 g | - | 3-mercaptoproyl trimethoxysilane |
Condensation, oxidation | 17.0 | 2.0 | 6.0 (50% RH) |
183 (100% RH) |
[132] |
a Measured at room temperature. b Determined by titration at 25 °C. c Proton conductivity at 80 °C. d Silica sulfonic acid. e Poly(4-styrenesulfonic acid) grafted core-shell silica particles. f Poly(4-vinylpyridine) grafted core-shell silica particles. g Sulfonated SBA-15 mesoporous silica