Publications

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