by Keyword: Electrical depolarization
Arnau, Marc, Sans, Jordi, Tamarit, Josep Lluis, Romanini, Michela, Turon, Pau, Aleman, Carlos, (2024). Unraveling Thermal Depolarization Phenomena in Biphasic Polarized Calcium Phosphate Catalyst Advanced Materials Interfaces , 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
