Speciation and Proton Conductivity of Phosphoric Acid Confined in Mesoporous Silica

TREVANI, LILIANA N.; LÉPORI, CRISTIAN M.O.; LINCK, YAMILA GARRO; MONTI, GUSTAVO A.; ABUIN, GRACIELA C.; CHÁVEZ, FABIÁN VACA; CORTI, HORACIO R.

ACS APPLIED MATERIALS & INTERFACES

AMER CHEMICAL SOC

Año: 2022 vol. 14 p. 33248 - 33248

1944-8244

hosphoric acid (PA) confined in a commercial mesoporous silica (CARIACT G) with porous size in the range of 3 to 10 nm was studied in relation to its coordination with the silanol groups on the silica surface as a function of temperature, up to 180 °C, using 31P and 29Si MAS NMR spectroscopy. As the temperature increases, the coordination of Si and P in the mesopores depends on the pore size, that is, on the area/volume ratio of the silica matrix. In the mesoporous silica with the higher pore size (10 nm), a considerable fraction of PA is nonbonded to the silanol groups on the surface, and it seems to be responsible for its higher conductivity at temperatures above 120 °C as compared to the samples with a smaller pore size. The electrical conductivity of the functionalized mesoporous silica was higher than that reported for other silico-phosphoric composites synthesized by sol−gel methods using soft templates, which require high-temperature calcination and high-cost reagents and