Sang Mi Lee

Bio: Sang Mi Lee is an academic researcher. The author has contributed to research in topics: Visible spectrum & Hydrogen. The author has an hindex of 11, co-authored 15 publications receiving 788 citations.

CdIn2S4 Nanotubes and “Marigold” Nanostructures: A Visible‐Light Photocatalyst

Abstract: Nanostructured photocatalysts with high activity are sought for solar production of hydrogen. Spinel semiconductors with different nanostructures and morphologies have immense importance for photocatalytic and other potential applications. Here, a chemically stable cubic spinel nanostructured CdIn2S4 prepared by a facile hydrothermal method is reported as a visible-light driven photocatalyst. A pretty, marigold-like morphology is observed in aqueous-mediated CdIn2S4, whereas nanotubes of good crystallinity, 25 nm in diameter, are obtained in methanol-mediated CdIn2S4. The aqueous- and methanol-mediated CdIn2S4 products show excellent photocatalytic activity compared to other organic mediated samples, and this is attributed to their high degree of crystallinity. The CdIn2S4 photocatalyst gives quantum yields of 16.8 % (marigold-like morphology) and 17.1 % (nanotubes) at 500 nm, respectively, for the H2 evolution reaction. The details of the characteristics of the photocatalyst, such as crystal and band structure, are reported. Considering the importance of hydrogen energy, CdIn2S4 will be an excellent candidate as a catalyst for “photohydrogen” production under visible light. Being a nanostructured chalcogenide semiconductor, CdIn2S4 will have other potential prospective applications, such as in solar cells, light-emitting diodes, and optoelectronic devices.

Semiconductor-based Photocatalytic Hydrogen Generation

Abstract: 2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Photoelectrocatalytic materials for environmental applications

Abstract: This feature article summarizes recent research on and development of semiconductor-based photocatalyst materials that are applicable to environmental remediation and/or chemical synthesis purposes. A wide variety of TiO2 particles and/or films have been studied during the past 30 years because they are the most stable and powerful photocatalysts leading to the degradation of various organic pollutants. The photocatalytic performance of other semiconductor materials such as ZnO, SnO2, WO3, Fe2O3 and CdS has also been intensively investigated. A general limitation in the efficiency of any photocatalytic process is the recombination of the photogenerated charge carriers, i.e., of electrons and holes, following bandgap illumination. Considerable efforts have been made to suppress this recombination and hence to enhance the charge carrier separation and the overall efficiency by means of coupling of different semiconductors with desirable matching of their electronic band structures, or incorporation of noble metal nanoclusters onto the surface of semiconductor photocatalyst particles. Modification of the physicochemical properties, such as particle size, surface area, porosity and/or crystallinity of the semiconductor materials, and optimization of the experimental conditions, such as pH, illumination conditions and/or catalyst loading, during photocatalytic reactions have also been carefully addressed to achieve high reaction rates or yields. To utilize solar energy more efficiently, i.e., to extend the optical absorption of the mostly UV-sensitive photocatalysts into the visible light range, numerous research groups have contributed to the development of novel visible light active photocatalysts. With the application of semiconductors with narrower bandgaps such as CdS, Fe2O3 and WO3 being straightforward choices, doping of wide bandgap semiconductors like TiO2 has been the most popular technique to enhance the catalysts' optical absorption abilities. Research on mixed-oxide-based semiconductor photocatalysts with deliberately modulated band structures has also attracted tremendous attention in the past decade, concentrating on, for example, the generation of H2 and/or O2 from H2O splitting, and the degradation of organic pollutants under visible light irradiation. Both theoretical calculations and experimental results have convincingly shown that the developed materials can serve as highly efficient photocatalysts that are both environmentally and economically significant.

α-Fe2O3 as a photocatalytic material: A review

Abstract: Photocatalysis has been attracting much research interest because of its wide applications in renewable energy and environmental remediation. There are many materials that are found to show good photocatalytic activity in the presence of ultraviolet (UV) and visible light. However, the applications of these materials are limited to the UV portion of sunlight. α-Fe 2 O 3 has an advantage over the other conventional materials like TiO 2 , ZnO, etc . in using solar energy for photocatalytic applications due to its lower band gap ∼2.2 eV value. As a result of which Fe 2 O 3 is capable of absorbing a large portion of the visible solar spectrum (absorbance edge ∼600 nm). Also its good chemical stability in aqueous medium, low cost, abundance and nontoxic nature makes it a promising material for photocatalytic water treatment and water splitting applications. Except these advantages the usage of Fe 2 O 3 has been restricted by many anomalies such as higher e–h recombination effect, low diffusion length and VB positioning (VB is positive with respect to H + /H 2 potential). This article reviews the research that has been carried out to overcome these basic limitations and to enhance the photocatalytic activity of α-Fe 2 O 3 .