High density heterogenisation of molecular electrocatalysts in a rigid intrinsically microporous polymer host

A water-insoluble Polymer with Intrinsic Microporosity (or PIM, here for the particular case of the Tröger Base system PIM-EA-TB, BET area ca. 103 m2 g−1) is demonstrated to act as a rigid host environment for highly water-insoluble molecular catalysts, here tetraphenylporphyrinato-iron (FeTPP), surrounded by aqueous solution-filled micropores. A PIM-EA-TB film containing catalyst is deposited onto the electrode and immersed for voltammetry (i) with 4-(3-phenyl-propyl)-pyridine to give an organogel, or (ii) bare directly into aqueous solution. The porous host allows processes to be optimised as a function of solution phase, composition, and catalyst loading. Effective electron transfer as well as effective electrocatalysis is reported for aqueous oxygen and peroxide reduction. Given the use of completely water-insoluble catalyst systems, the methodology offers potential for application with a wide range of hitherto unexplored molecular electrocatalysts and catalyst combinations in aqueous media. Keywords: Electrocatalysis, Ion transfer, Peroxide, Oxygen, Fuel cell, Sensin

Intrinsically porous polymer protects catalytic gold particles for enzymeless glucose oxidation

The enzymeless glucose oxidation process readily occurs on nano-gold electrocatalyst at pH 7, but it is highly susceptible to poisoning (competitive binding), for example from protein or chloride. Is it shown here that gold nanoparticle catalyst can be protected against poisoning by a polymer of intrinsic microporosity (PIM-EA-TB with BET surface area 1027 m2 g−1). This PIM material when protonated, achieves a triple catalyst protection effect by (i) size selective repulsion of larger protein molecules (albumins) and (ii) membrane ion selection effects, and (iii) membrane ion activity effects. PIM materials allow “environmental control” to be introduced in electrocatalytic processes

Gas-phase FT-IR analysis and growth kinetics of Al2O3 in a LP-MOCVD reactor using new dialkylacetylacetonate precursors

Gas-phase FT-IR spectroscopy has been employed to study the thermal decomposition of dialkylacetylacetonate aluminium (alkyl = metyl, ethyl and iso-buthyl) in a hot-wall LP-MOCVD (low-pressure metal organic chemical vapour deposition) system. On the basis of such preliminary data, growths of alumina have been carried out using methyl- and ethyl derivatives in a spread range of experimental conditions : reactor temperature 400-520 °C and total pressure 100-400 Pa. Aluminium oxide films have been grown in a nitrogen atmosphere either in the presence of oxygen or water vapour. In both cases the obtained films are amorphous, smooth and well adherent, but they are black in the first case, transparent and slightly yellowish in the second one. A simple theoretical kinetic model was applied to analyse and rationalise the experimental data related to the diethylacetylacetonate aluminium precursor. The model well predicts the deposition rates attributed to the rate determining step of the heterogeneous process with an activation energy of 97 kJ mol-1 in the presence of oxygen, and 49 kJ mol-1 in the presence of water vapour

Al2O3 growth optimisation using aluminium dimethylisopropoxide as precursor as a function of reaction conditions and reacting gases

Aluminum oxide films were grown in a hot-wall low-pressure metal organic chemical vapor deposition (MOCVD) system using aluminum dimethylisopropoxide as precursor. Experimental reaction conditions and the reacting gas (O2, H2O, N2O) have been systematically varied with the aim to decrease the deposition temperature and obtain transparent, dense and carbon-free films. Changes in the gas phase composition were studied by FT-IR spectroscopy using an in-line cell. The reactor temperature ranged from 230 °C to 380 °C. The microstructure of the films was investigated by X-ray Diffraction, while the surface chemical composition was studied by X-ray Photoelectron. Atomic Force Microscopy was employed to analyze the surface morphology of the films as a function of reaction conditions and reacting gases. The best performances have been obtained using dry oxygen at 1000 Pa and oxygen mixed with water vapor at 100 Pa. High growth rates such as 140 nm min-1 have been obtained at 270 °C in the latter case. Different reaction mechanisms have been proposed in the two cases