Hydrogenolysis cleavage of Csp2-Csp3 bond over a metal-free NbOPO4 catalyst

Ru/NbOx catalysts, which combine the merits of facile hydrogen activation, strong binding to benzene ring and the presence of Brønsted acid sites, were well investigated toward Csp2-Csp3 bond cleavage. Herein, we unlock the ability of bare NbOx catalyst in the dissociation and activation of hydrogen molecule and further hydrogenolysis of the Csp2-Csp3 model compounds including polystyrene (PS). In-situ Drift and density functional theory (DFT) calculations reveal that H2 can be dissociated and surface hydride species can be produced over Nb2O5 through heterolytic and homolytic cleavages of H2. We also find that the existence of surface oxygen vacancies plays a key role in stabilizing hydride species. Further, the NbOPO4 catalyst not only allows the conversion of phenylcyclohexane to monocyclic compounds by cleaving Csp2-Csp3 bond, but also enables the conversion of PS to arenes with a high selectivity. This study provides and proves for the first time, the unique ability of metal oxides (phosphates) in the hydrogenolysis of compounds and plastics containing Csp2-Csp3 bonds.

Low Temperature HCHO Detection by SnO2/TiO2@Au and SnO2/TiO2@Pt: Understanding by in-situ DRIFT Spectroscopy

In this work we analyze the effectiveness of decoration of nanocrystalline SnO2/TiO2 composites with gold nanoparticles (Au NPs) and platinum nanoparticles (Pt NPs) in enhancing gas sensor properties in low-temperature HCHO detection. Nanocrystalline SnO2/TiO2 composites were synthesized by a chemical precipitation method with following modification with Pt and Au NPs by the impregnation method. The nanocomposites were characterized by TEM, XRD, Raman and FTIR spectroscopy, DRIFTS, XPS, TPR-H2 methods. In HCHO detection, the modification of SnO2 with TiO2 leads to a shift in the optimal temperature from 150 to 100 °C. Further modification of SnO2/TiO2 nanocomposites with Au NPs increases the sensor signal at T = 100 °C, while modification with Pt NPs gives rise to the appearance of sensor responses at T = 25 °C and 50 °C. At 200 °C nanocomposites exhibited high selectivity toward formaldehyde within the sub-ppm concentration range among different VOCs. The influence of Pt and Au NPs on surface reactivity of SnO2/TiO2 composite and enhancement of the sensor response toward HCHO was studied by DRIFT spectroscopy and explained by the chemical and electronic sensitization mechanisms.