Joel B. DuBow

Bio: Joel B. DuBow is an academic researcher from Colorado State University. The author has contributed to research in topics: Oil shale & Thermal diffusivity. The author has an hindex of 17, co-authored 72 publications receiving 1338 citations.

Thermophysical properties of oil shales

Abstract: Recent developments in the characterization of the thermophysical properties of various types of oil shales are reviewed. Changes in the thermal, mechanical and electrical properties of these technologically important materials are discussed, with temperature and organic content as the experimental variables. Structural models are presented to aid in predicting the variation of thermophysical parameters with organic content in the shale. Comparison of calculated results with experimental data are shown with thermal diffusivity as a representative parameter. Areas where further research of a fundamental nature would be of particular relevance are also highlighted in the review.

Heterojunction Silicon/Indium Tin Oxide Photoelectrodes: Development of Stable Systems in Aqueous Electrolytes and Their Applicability to Solar Energy Conversion and Storage

Abstract: An approach to circumvent the problem of poor photoelectrochemical (PEC) stability of Si in aqueous electrolytes is the use of heterojunction photoelectrodes comprising the Si/SiO/sub x// indium tin oxide (ITO) structure. As in a Schottky barrier electrode system, the maximum photovoltage attainable with these electrodes is limited by the barrier height at the Si/ITO heterojunction. Both n- and p-Si substrates have been studied. In regenerative PEC systems designed for the conversion of solar energy to electricity, the efficacy of charge transfer at the ITO/electrolyte interface is shown to be a crucial factor. Of the redox electrolytes tested (S/sup 2 -//S/sup 2 -//sub x/,, I/sup 3 -//I/sup -/, (Fe(CN)/sub 6/)/sup 3-/4-/ and Fe/sup 2+/3+/ EDTA), the (Fe(CN)/sup 6//sup 3-/4-/ couple was by far the most efficient in terms of charge transfer across the ITO/electrolyte interface. Optical-to-electrical conversion efficiencies (eta) of 1.57% and 5.7% (approx. AM 1 illumination) were attained for PEC cells based on n- and p-Si substrates, respectively. Detailed tests have revealed long-term stability in (Fe(CN)/sub 6/)/sup 3-/4-/ electrolytes once the ITO film thickness (greater than or equal to 50 A) and solution pH (approx. 12 to 14) were optimized, n-Si/ITO electrodes were used for the photooxidation of Cl/sup -/more » from concentrated LiCl and NaCl electrolytes to illustrate the chemical inertness and stability of these electrodes. Catalytic modification of the ITO surface with RuO/sub 2/ was found to be necessary to sustain Cl/sub 2/ production. Values of eta up to 2.7% were recorded with this PEC system at 100 mW/cm/sup 2/. Finally, the applicability of Si/ITO heterojunction electrodes for the photoassisted splitting of water was demonstrated. Preliminary experiments have revealed a 40% reduction in the threshold voltage required for water photolysis. Catalytic modification of the ITO surface was again a prerequisite for efficient performance of these electrodes.« less

Inorganic nanostructures for photoelectrochemical and photocatalytic water splitting

Abstract: The increasing human need for clean and renewable energy has stimulated research in artificial photosynthesis, and in particular water photoelectrolysis as a pathway to hydrogen fuel. Nanostructured devices are widely regarded as an opportunity to improve efficiency and lower costs, but as a detailed analysis shows, they also have considerably disadvantages. This article reviews the current state of research on nanoscale-enhanced photoelectrodes and photocatalysts for the water splitting reaction. The focus is on transition metal oxides with special emphasis of Fe2O3, but nitrides and chalcogenides, and main group element compounds, including carbon nitride and silicon, are also covered. The effects of nanostructuring on carrier generation and collection, multiple exciton generation, and quantum confinement are also discussed, as well as implications of particle size on surface recombination, on the size of space charge layers and on the possibility of controlling nanostructure energetics via potential determining ions. After a summary of electrocatalytic and plasmonic nanostructures, the review concludes with an outlook on the challenges in solar fuel generation with nanoscale inorganic materials.