No abstract

Metal-organic frameworks (MOFs) have emerged as a new class of supports for metal nanoparticles(NPs) in heterogeneous catalysis because of possible synergetic effects between the two components. In addition, MOFs also can be coated over metal NPs to influence the entire nanoparticle's surface. Herein, NPs were hybridized with UiO-66(Hf) MOF possessing Brønsted acidic sites (on secondary building units) and fabricated Pd@UiO-66 (Hf) core-shell and Pd/UiO-66(Hf) supported catalysts. These hybrid materials exhibited enhanced catalytic properties (TOF increased up to 2.5 times) compared to individual counterparts or their physical mixture for dehydrogenation of ammonia borane(AB) in non-aqueous medium(1,4-dioxane). Further, nanostructure of the hybrid material had pronounced influence on the catalytic properties. The core-shell catalyst exhibited highest activity towards H generation from AB owing to greater contact interface between Pd and MOF. Further, phenylacetylene semi-hydrogenation with AB over Pd@UiO-66 (Hf) furnished styrene selectivity as high as 93.2 % at ∼100 % conversion mostly due to the regulated phenylacetylene diffusion through UiO-66(Hf) shell.

No abstract

Photoelectrochemical (PEC) water splitting is one of the most desirable techniques to harvest clean chemical energy from abundant solar energy. However, the anodic half reaction, i.e., water oxidation, is complicated due to the involvement of multiple electrons in this process. Herein, stable WO 3 nanoblocks with the monoclinic phase have been modified by the incorporation of hexagonal boron nitride quantum dots (h-BNQDs) to improve the photogenerated electron−hole separation and additionally to hinder the charge recombination process. The photocurrent density (J) value for the modified WO 3 photoanode by incorporation of BNQDs has been found to be 1.63 mA/cm 2 at the potential of 1.23 V RHE , which is approximately 2.4-fold higher than the bare WO 3 photoanode. The enhancement in photocurrent density is mainly due to the hole extraction property of BNQDs on the surface of the WO 3 nanoblocks. A 2-fold increment in photogenerated charge carrier density (N D ) value has been achieved due to better charge separation of electron−hole pairs in the modified system, confirmed by the Mott−Schottky (MS) plot. The present work demonstrates a unique, low-cost strategy for enhancement of PEC water oxidation by modification of the photoanode with hole extracting agents.

No abstract

Catalytic total oxidation is important in several applications. However, associated models are rather empirical. In this study, a microkinetic model is developed for ethane total oxidation, under fuel-lean conditions on a Pt catalyst using input from density functional theory and Brønsted−Evans−Polanyi linear free energy relations. Reaction orders and the apparent activation energy estimated from the model are in good agreement with experimental values. The inclusion of oxygen coverage effects on the activation of ethane changes the rate-determining step from thermal dehydrogenation to oxidative dehydrogenation of ethane. A significant portion (30%) of the reaction flux proceeds via oxygen insertion reactions to C 2 hydrocarbons (CH 2 C*).

No abstract

No abstract