Fehmida K. Kanodarwala

Titania supported MOF-199 derived Cu–Cu2O nanoparticles: highly efficient non-noble metal photocatalysts for hydrogen production from alcohol–water mixtures

Fabrication of cheap and efficient photocatalysts is pivotal for practical applications of solar energy devices. Here, we illustrate a novel trend in generating Cu–Cu2O nanoparticles over TiO2 for water splitting systems. Titanium(IV) isopropoxide was hydrolysed in the presence of various wt% of MOF-199 ([Cu3(BTC)2(H2O)3]n) to obtain TiO2–MOF-199 composite materials. These composite materials are then calcined at various temperatures in air to produce highly dispersed Cu–Cu2O nanoparticles over TiO2; these nanoparticles were tested as photocatalyts for hydrogen generation from alcohol–water mixtures. The photocatalyst 1 wt% Cu/TiO2-400 was found to exhibit a hydrogen production rate some 2.5 times higher than that of CuO prepared by conventional precipitation methods. The calcination temperature of the TiO2–MOF composite was found to affect the oxidation state of Cu and the photocatalytic activity, with an optimum performance achieved at 400 °C. Calcination beyond this temperature led to oxidation and agglomeration of Cu–Cu2O nanoparticles into larger CuO deposits, which reduce the H2 production activity (ca. 80%).

Pd–Ag decorated g-C3N4 as an efficient photocatalyst for hydrogen production from water under direct solar light irradiation

A low visible light absorption efficiency and high recombination rate of photogenerated charge carriers are two major problems encountered in graphitic carbon nitride (g-C3N4) based photocatalysts for water splitting applications. In this work, Pd–Ag bimetallic and monometallic nanoparticles were decorated on graphitic carbon nitride by a simple chemical reduction method and evaluated for their ability to produce H2 during water splitting reactions. The physical and photophysical characteristics of the as-prepared Pd–Ag/g-C3N4 photocatalysts were studied by powder X-ray diffraction (PXRD), UV-visible diffuse reflection spectroscopy (DRS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and steady state photoluminescence (PL). The Pd0.7–Ag0.3/g-C3N4 photocatalyst with an overall metal loading of 1 wt% showed a very high H2 generation rate of 1250 μmol h−1 g−1, which is 1.5 and 5.7 times higher than those of the Pd/g-C3N4 and Ag/g-C3N4 photocatalysts, respectively. The high activity of the Pd–Ag/g-C3N4 photocatalyst was attributed to the inherent property of palladium metal to quench photogenerated electrons by the Schottky barrier formation mechanism and strong visible light absorption due to the characteristic surface plasmon resonance (SPR) of silver nanoparticles along with the absorption of g-C3N4.

Synthesis and characterization of organic–inorganic hybrid materials prepared by sol–gel and containing CdS nanoparticles prepared by a colloidal method using poly(N-vinyl-2-pyrrolidone)

This paper describes the synthesis and characterization of CdS nanoparticles (NPs) stabilized with poly(N-vinyl-2-pyrrolidone) and their further immobilization on a hybrid organic–inorganic matrix produced by the sol–gel process. The production of the hybrid matrix doped with CdS NPs was carried out in two steps. In the first step a precursor, designated diureasil precursor, was synthesized from the reaction between the terminal amine groups of α,ω-diamine-poly(oxyethylene-co-oxypropylene) and the isocyanate group of 3-isocyanatopropyltriethoxysilane. The next step involved the hydrolysis and condensation reactions of ethoxy groups attached to silicon, this step resulting in the formation of a crosslinked siliceous network linked through urea bonds to a poly(oxyethylene)/poly(oxypropylene) chain. The NPs were added to the diureasil precursor before the gelation process to allow a homogeneous dispersion of the NPs within the matrix. The developed method allowed the transfer of colloidal NPs to a solid matrix without the need of exchange the capping agents or the solvent. The materials were characterized by absorption, steady-state photoluminescence spectroscopy and by TEM. The results obtained showed the presence of CdS NPs with quantum size effect dispersed within the diureasil matrix. The obtained nanocomposites show a high transparency in the visible range accounting for the good dispersion of the NPs within the matrix. The TEM analysis confirmed that the NPs are uniformly dispersed within the diureasil matrix.