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by Keyword: Tsp treatment
Arnau, Marc, Teixido, Isabel, Turon, Pau, Aleman, Carlos, Sans, Jordi, (2025). Lattice Engineering in Hydroxyapatite Enables Direct Photocatalytic Synthesis of C4 Products from CO2 Acs Applied Materials & Interfaces 17, 70621-70633 
Amid the burst of carbon dioxide (CO2) capture and conversion technologies, research prioritizing industrially feasible catalysts is vital to minimize climate change effects. In the present work, permanently polarized hydroxyapatite-based biphasic systems have been strategically designed through vacancy engineering and a thermally stimulated polarization (TSP) process, achieving a 15% selectivity toward C-3-C-4 products through a single-step CO2 continuous-flow reaction (CO2-to-C3+) under solar light irradiation and mild reaction conditions. To elucidate the underlying catalytic mechanism, extensive experimental characterization has been performed in combination with theoretical density functional theory (DFT) calculations. More specifically, Raman spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy have been used for structural characterization, and electrochemical impedance spectroscopy studies have been performed to determine charge conduction customization. On the other hand, DFT calculations have been employed to determine the photocatalytic contribution by determining the density of states and band diagrams. The results have been further supported by UV-vis experimental measurements, facilitating the elucidation of the mechanisms behind the photoexcited electrons through band gap trap state generation. Finally, additional adsorption energy studies, combined with Bader charge analysis and Nudge elastic band calculations, have allowed the identification of the binding sites responsible for C3+ molecule growth as far as the CO2 dissociation pathway and respective energy barrier. These results highlight the role of the crystal lattice vacancies in the CO2 bond-cleavage process and represent a huge step toward the design of efficient and scalable catalysts for CO2-to-C3+ production.
JTD Keywords: Co2 valorization, Co2-to-c3+, Enhanced electrical properties, Green catalysis, Permanentlypolarizedhydroxyapatite, Tsp treatment
Arnau, M, Sanz, J, Turon, P, Alemán, C, Sans, J, (2025). Green Synthesis of Urea from Carbon Dioxide and Ammonia Catalyzed by Ultraporous Permanently Polarized Hydroxyapatite Chempluschem 90, e202400705-e202400705
The sustainable synthesis of urea from ammonia (NH3) and carbon dioxide (CO2) using ultraporous permanently polarized hydroxyapatite (upp-HAp) as catalyst has been explored as an advantageous CO2-revalorization strategy. As the simultaneous activation of N-2 and CO2 (single-step) demands an increase of the reaction conditions, we have re-visited the industrial two-step Bazarov reaction. upp-HAp has been designed as a stable multifunctional catalyst capable of promoting both CO2 and NH3 adsorption for their subsequent C-N bond formation. Herein we report the synthesis of 1 mmol/g(cat) of urea with a selectivity of 97 % under strictly mild conditions (95-120 degrees C and 1 bar of CO2; without applying any electrical currents or UV irradiation) which represents an efficiency of similar to 2 % and similar to 30 % with respect to the NH3 and CO2 content, respectively. The study of the NH3 content, products adsorbed in the catalyst, presence of intermediates and temperature of the reaction allows unveiling the great potential of upp-HAp as a green catalyst for sustainable Bazarov reactions. Results suggest that the double-step approach could be more advantageous for both synthesizing urea and as a CO2-revalorization strategy, which in turn promotes the development of specific technologies for the independent synthesis of green NH3.
JTD Keywords: Co2-revalorization, Hydroxyapatite, Permanently polarized materials, Tsp treatment, Ure, Urea
