by Keyword: Green catalysts
Arnau, M, Sans, J, Tamarit, JL, Romanini, M, Turon, P, Alemán, C, (2024). Unraveling Thermal Depolarization Phenomena in Biphasic Polarized Calcium Phosphate Catalyst Advanced Materials Interfaces 11, 2400422 
Permanently polarized biphasic calcium phosphate composed of hydroxyapatite and brushite (pp-HAp/Bru), which is prepared by applying the thermally stimulated polarization treatment to calcined HAp, is used as a sustainable catalyst to transform CO2 into value-added products. In this work, the stability of pp-HAp/Bru is studied from structural, electrical, and catalytic perspectives, applying a thermal depolarization process with temperatures (T-d) ranging from 200 to 1000 degrees C. Results show that the Bru phase is not stable when T-d = 600 degrees C. Besides, the electrical resistance and capacitance of the pp-HAp/Bru increase with T-d, evidencing the progressive electrical depolarization of the material. Thermal depolarization also influences the specific orientation of the OH- ions, which is partially lost (approximate to 50%). All such changes affect the catalytic efficiency of pp-HAp/Bru, which is proven using a reaction that transforms CO2 gas into acetic acid and formic acid. Results show that the total reaction yield linearly decreases with increasing T-d. Based on such observations, a simple process is designed that allows the reconstitution of the structure and restores the activity of such green catalysts.
JTD Keywords: Co-2 fixation, Electrical depolarization, Green catalysts, Interface stability, Thermal depolarizatio
