Publications

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

Catalytically active hydroxyapatite (ca-HAp) decorated with zirconia nanoparticles (ZrO2 NPs) is presented as a nanocomposite catalyst (ca-HAp/ZrO2) capable of performing highly efficient nitrogen to ammonia (N2-to-NH3) fixation reactions under mild conditions. Accordingly, reactions were carried out in a batch reactor operating at 120 degrees C, 6 bar of N2, and 20 mL of water, under UV irradiation (14 W) for 72 h. The yield of NH3 obtained was 1.592 +/- 0.146 mmolgc -1, which represents a N2 fixation efficiency of 6.4%. Near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) studies under in situ conditions (i.e., at elevated pressure and temperature and during UV irradiation) and density functional theory simulations (DFT) allowed us to elucidate the catalytic mechanism of the system. The ca-HAp/ZrO2 nanocomposites exhibit a strong synergy arising from the initial photoactivation of N2 by means of the pi-backdonation mechanism in ZrO2 (N2 is anchored by four Zr4+ atoms) followed by the dinitrogen spillover toward the Ca(I)2+ binding sites. Such sites, preferentially exposed in the (001) crystallographic planes of ca-HAp, show high activity due to the enhanced electron transfer properties of ca-HAp. These catalytic nanocomposites represent a viable alternative to the conventional catalysts used for N2-to-NH3 fixation reactions.

JTD Keywords: Amino-acids, Approximation, Catalyst, Electron enhancedproperties, Green catalysis, Hydroxyapatite, N-2 reduction, Permanently polarizedmaterial, Pi-back-donation, Polarized hydroxyapatite, Pressur, Temperature