The direct synthesis of hydrogen peroxide (H2O2) from molecular hydrogen and oxygen could represent a green and economically attractive alternative to the current indirect anthraquinone process used for the industrial production of hydrogen peroxide. This reaction has been investigated using palladium supported on the Cs-containing heteropolyacid Cs2.5H0.5PW12O40. In addition, the effect of adding copper as a potential activity promoter was investigated. These catalysts were also evaluated for the subsequent degradation of hydrogen peroxide. The catalytic activity of the 0.5 wt.%Pd/Cs2.5H0.5PW12O40 catalyst towards hydrogen peroxide synthesis was greater than that of both the mono-metallic Cu or bi-metallic Pd-Cu analogues with the incorporation of Cu to Pd resulting in a significant decrease in catalytic selectivity for the formation of hydrogen peroxide. Moreover, 0.5 wt.%Pd/Cs2.5H0.5PW12O40 also showed low activity towards the degradation of hydrogen peroxide. Hence the use of the Cs-containing heteropolyacid as a support for Pd gives higher rates of hydrogen peroxide formation when compared with different supported Pd catalysts prepared using supports used in previous studies.

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This work provides an alternate unique simple methodology to design and synthesize chemically modified nanophotocatalyst based on high surface area TiO2 nanoparticles that can be used efficiently for the photodegradation of organic pollutants under normal visible light rather than complicated UV irradiation. In this study, dual visible light and UV-driven nanophotocatalysts were synthesized via wet chemistry procedures using high surface area TiO2 nanoparticles functionalized with (3-Aminopropyl) trimethoxysilane and attached chemically to the CuXO to improve the charge separation and maintain the non-charge recombination. The successful modification of the TiO2 nanoparticles and the formation of the TiO2-NH2-CuxO nanophotocatalyst were confirmed using different characterization techniques, and the results revealed the synthesis of high surface area TiO2 nanoparticles, and their chemical modification with an amino group and further decoration with copper to produce TiO2-NH2-CuxO nanophotocatalyst. The photocatalytic activity of TiO2 and TiO2-NH2-CuxO nanophotocatalyst were evaluated using methylene blue (MB) dye; as an example of organic pollutants. The resulting TiO2-NH2-CuxO nanophotocatalyst exhibited superior photocatalytic activity for the degradation of MB dye under visible light irradiation, due to the reduction in the energy bandgap. The degradation of the MB dye using the TiO2-NH2-CuxO nanophotocatalyst was investigated using LC-MS, and the results revealed that the hydroxyl free radical is mainly responsible for the cleavage and the degradation of the MB dye.

The synthesis of dimethyl carbonate (DMC) from methanol and Carbon dioxide (CO2) has been investigated over 5% Rh/Al2O3 catalyst. Diffuse Reflectance Infrared Fourier Transfer Spectroscopy (DRIFTS) was used to probe the reaction adsorbates which showed that activation of methanol and CO2 involves generation of intermediate methoxy species and formate ingredients, participating in elementary steps of DMC formation. Formation of DMC involves parallel routes comprising interaction of the OH group of Al2O3 through an acid/base mechanism and formate pathway with participation of metal sites. DMC in acid/base pathway is formed via methoxy species to form methoxy carbonate (CH3O)CO2 (active adsorbate), which then reacts with the methyl species to form DMC. The pathway involving metal Rh sites generates an additional elementary step for the involvement of CO2 in the reaction through active formate species. The synergy of parallel pathways determines the performance of the 5% Rh/Al2O3 catalyst. Further improvement of catalyst performance should be based on such a feature of the reaction mechanism.

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