Frank S. Stone

Bio: Frank S. Stone is an academic researcher from University of Bath. The author has contributed to research in topics: Adsorption & Catalysis. The author has an hindex of 20, co-authored 56 publications receiving 1513 citations. Previous affiliations of Frank S. Stone include Sapienza University of Rome & Keele University.

UV reflectance and FTIR spectroscopic studies of CO adsorption and reaction on lanthanum oxide

Abstract: Microcrystalline La2O3 outgassed at 873 K has a UV absorption edge centred at ca. 250 nm on which absorption ascribable to surface states is superimposed. This latter absorption is diminished by CO2 adsorption, which produces surface carbonate. UV reflectance and IR results with CO are correlated to show that CO adsorption on the outgassed oxide occurs with rapid formation of carbonite CO22– ions, accompanied at room temperature by a slow reaction forming reduced oligomeric (CO)n2– anions and carbonate CO32–. The reaction stages have been resolved by extending the UV and IR measurements to low temperatures. CO22–, identified by UV absorption at 340 nm and IR bands at 1390 and 987 cm–1, is the only process occurring at 90 K. As the temperature is increased, the ketenic dimer anion C2O32– is formed, characterized by a UV band at 300 nm and IR bands at 2075 and 1367 cm–1. The onward disproportionation producing reduced oligomers and carbonates gives a complex IR spectrum in the 1700–1000 cm–1 range. The bands due to the oligomers are readily discriminated by their sensitivity to oxygen. The discussion illustrates that UV and IR spectroscopy afford a powerful combination in defining and understanding the stages involved in the adsorption and reaction of CO on lanthanum oxide. The nature and extent of the reactivity towards CO shows that the basicity of La2O3 is not as great as that of the alkaline-earth-metal oxides.

Structural characterization of cadmium–copper gallium oxide (CdxCu1–xGa2O4) spinels

Abstract: CdGa2O4, CuGa2O4 and four ternary spinels CdxCu1–xGa2O4 have been prepared by solid-state reaction of mixtures of CdO, CuO and Ga2O3 at 1223 K. X-ray powder diffractometry has been used to determine the unit-cell parameter, a0, the oxygen parameter, u, and the respective distributions of Cd2+, Cu2+ and Ga3+ in tetrahedral and octahedral coordination, by applying a computational method to compare observed and calculated diffraction intensities. The capability of the method has been tested for CuGa2O4, where the Cu2+(3d9) and Ga3+(3d10) ions have similar scattering powers, by comparing the results with data from neutron diffraction.CdGa2O4 and CuGa2O4 are 15 and 84% inverse, respectively. Interdependence of a0, u and the cation distribution is closely analysed for CdxCu1–xGa2O4, where the behaviour of the ternary system gives new insight into the oxide crystal chemistry. The steric effects on lattice distortion are discussed alongside the covalent contribution in the metal–oxygen bonds, which is manifested in the strong tetrahedral preferences of Cd2+ and Ga3+ ions.

Dispersed-Metal/Oxide Catalysts Prepared By Reduction Of High Surface Area Oxide Solid Solutions

Abstract: Superficial reduction of dilute NixMg1-xO and CoxMg1-xO, solid solutions of high specific surface area yields supported Ni and Co catalysts with high metal dispersion. Reduction by both H2 and CO are described. With CO the Boudouard reaction intervenes at 500-600°C, and thus reduction is self-regulating. The oxygen uptake by the reduced solid solutions, studied as a function of temperature, enables exsolved Ni and Co to be discriminated from that present in the matrix. The extent of reduction controls the selectivity in CO hydrogenation.

Recent advances in catalytic hydrogenation of carbon dioxide

Abstract: Owing to the increasing emissions of carbon dioxide (CO2), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO2 in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO2. Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO2, offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO2 not only reduces the increasing CO2 buildup but also produces fuels and chemicals. In this critical review we discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references).

Quantum Dot Solar Cells. Tuning Photoresponse through Size and Shape Control of CdSe−TiO2 Architecture

Abstract: Different-sized CdSe quantum dots have been assembled on TiO2 films composed of particle and nanotube morphologies using a bifunctional linker molecule. Upon band-gap excitation, CdSe quantum dots inject electrons into TiO2 nanoparticles and nanotubes, thus enabling the generation of photocurrent in a photoelectrochemical solar cell. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via size control of CdSe quantum dots and (ii) improvement in the photoconversion efficiency by facilitating the charge transport through TiO2 nanotube architecture. The maximum IPCE (photon-to-charge carrier generation efficiency) obtained with 3 nm diameter CdSe nanoparticles was 35% for particulate TiO2 and 45% for tubular TiO2 morphology. The maximum IPCE observed at the excitonic band increases with decreasing particle size, whereas the shift in the conduction band to more negative potentials increases the driving force and favors fast electron injection. The maximum power-conversion efficiency

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment

Abstract: CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does...

Heterogeneous catalytic decomposition of nitrous oxide

Abstract: An overview is given on the ongoing activities in the area of the decomposition of nitrous oxide, N2O, over solid catalysts. These catalysts include metals, pure and mixed oxides, supported as well as unsupported, and zeolitic systems. The review covers aspects of the reaction mechanism and kinetics, focusing on the role of surface oxygen, the inhibition by molecular oxygen, water and other species, poisoning phenomena and practical developments.