Journal
CHEMICAL JOURNAL OF CHINESE UNIVERSITIES-CHINESE
Volume 43, Issue 4, Pages -Publisher
HIGHER EDUCATION PRESS
DOI: 10.7503/cjcu20210833
Keywords
Layered double hydroxide; Points of zero charge; Interface acid-base reaction; Interface-charging model; Acid-base titration
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Funding
- National Natural Science Foundation of China [21872082,21573133]
- Natural Science Foundation of Shandong Province,China
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This study synthesized five Mg-Al-Ti-CO3 layered double hydroxides using a coprecipitation method and investigated their crystal structure and interface electrochemical properties. The results showed that an increase in R-Ti led to changes in the crystal structure and a decrease in the deprotonation tendency of surface hydroxyl groups.
Five Mg-Al-Ti-CO3 layered double hydroxides (LDHs) were synthesized using a coprecipitation method with a constant Mg2+/(Al3++Ti4+) molar ratio of 3.00 but varying Ti4+/(Al3++Ti4+) molar ratio (R-Ti, 0-0.40). Their structural charge density (sigma(st)), point of zem net charge (pH(PZNC)), and point of zero net proton charge (pH(PZNPC)) were determined using potcntiomctric, salt and potcntiomctric mass titrations, and their intrinsic equilibrium constants of surface acid-base reactions (pK, pK(a1)(int) and pK(a2)(int)) were estimated in turn based on the general 1-pK and 2-pK models. Special emphasis was placed on the effect of R-Ti on their crystal structure and interface electrochemical (IEC) properties. With an increase in R-Ti the cell constants (a, b and c) and d-spacing increase, arising from the strong electrostatic repulsion between Ti4+ ions. An increase tendency was also observed for pH(PZNC), pH(PZNPC), pK, pK(a1)(int) and pK(a2)(int) with the increase of R-Ti, indicating a decrease in the depmtonation tendency of surface hydroxyl groups. In addition, it was observed that pH(PZNPC) is lower than pH(PZNC) and increases with increasing the electrolyte (NaNO3) concentration, arising from the effect of structural charges. This work provides a better understanding for the IEC properties of Ti4+- containing LDHs.
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