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.

Thermal behaviour of γ-MnO2 and some reduced forms in oxygen

Abstract: The products obtained by partial chemical reduction of an electrodeposited γ-manganese dioxide have been studied by thermal analysis in an oxygen environment between room temperature and 725 K. Weight loss in the temperature range 430–520 K was independent of sample composition when up to 35 % of MnIV was replaced by MnIII. Substitution of > 50 % MnIV led to a dependence of weight loss on degree of reduction. With the aid of X-ray diffractometry and magnetic susceptibility measurements, these results could be explained by the formation of a single phase solid solution below ∼50 % reduction and a two-phase system when greater amounts of MnIII were incorporated into the solid.Weight loss in the neighbourhood of 630 K could be resolved into two entities. The low temperature component was associated with the phase transition from γ-MnO2 to β-MnO2 accompanied by some loss of oxygen. The high temperature component was attributed to the loss of water resulting from the decomposition of Mn(OH)4.

Synthesis and structural characterization of CuAl2O4–CdAl2O4 spinel solid solutions

Abstract: CuAl2O4 and cadmium-containing spinel solid solutions CdxCu1–xAl2O4 have been prepared by solid-state reaction of mixtures of CuO, CdO and Al2O3 at 1223 K. The spinels, which are cubic, have been studied by X-ray powder photography and diffractometry. The cation distributions and the oxygen parameter u have been determined using a statistical method to compare observed and calculated X-ray intensities. It is shown that Cd2+ ions enter tetrahedral sites exclusively, but that simultaneously there is displacement of some of the remaining Cu2+ from tetrahedral to octahedral sites. For CdxCu1–xAl2O4 at x= 0 the spinel is 35% inverse and inversion increases to 43% at x= 0.50. A solubility limit for Cd2+ in the spinel phase is reached at x= 0.58. The reaction of CdO with Al2O3 does not produce a spinel.The results are discussed in terms of the balance developed between the covalency introduced by Cd2+ ions and the disturbance caused to the electrostatic energy by the enlargement of the tetrahedral sites. This enlargement is quantified by measured increases in the unit-cell parameter and the oxygen parameter.

UV-Visible Diffuse Reflectance Spectroscopy Applied to Bulk and Surface Properties of Oxides and Related Solids

Abstract: The theory and practice of diffuse reflectance spectroscopy in the spectral range from 50,000 cm-1 to 5,000 cm-1 (UV-vis-near IR) are described. The Kubelka-Munk equation is derived and the experimental technique required for diffuse reflectance work is discussed. Application to non-metallic solids is illustrated first with reference to spectra arising from d-d transitions and then with regard to charge-transfer spectra. Particular attention is given to reflectance studies of surface properties and to measurements in the presence of gases. The UV-vis spectra of adsorbed molecules are treated with special reference to the spectra of chemisorbed species formed by reactions at the surfaces of acidic and basic oxide catalysts.

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.