| Abstract
| - The ordered 2D-hexagonal mesoporous structure of Mg−Ta oxide (123 m2 g-1 BET surface area, 5.0 nm pore size, and 2.8 nm wall thickness) is completed in the initial stage of calcination for template removal but not achieved after aging. The mesoporous Mg−Ta oxide shows high photocatalytic activity for overall water decomposition.
- An ordered (2D-hexagonal) mesoporous Mg and Ta mixed oxide (Mg−Ta oxide) issuccessfully prepared. The mesoporous Mg−Ta oxide is stable after calcination at 773 K for30 h, and has a BET surface area of 123 m2 g-1, pore size of 5.0 nm, and wall thickness of2.8 nm. Removal of the template by washing in water results in a wormhole-like microporousmaterial with a BET surface area of 424 m2 g-1. The ordered mesoporous structure is notachieved after aging alone (313 K), but becomes complete through structural rearrangementin the initial stage of calcination (<423 K) for template removal. The presence of the templateduring calcination is found to be indispensable, and the ordered mesoporous material is notobtained when the template is removed by washing with water prior to calcination. Althoughthe inorganic phase is amorphous, the photocatalytic activity for overall water decompositionover the 2D hexagonal mesoporous Mg−Ta oxide is much higher than over crystallizedMgTa2O6. The highest activity (ca. 100 μmol h-1 for H2 and 50 μmol h-1 for O2) is attainedby loading with 0.1 wt % NiO followed by reduction and reoxidation pretreatment.
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