Lanthanide (III) (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) Ions Loaded in CeO₂ Support; Fundamental Natures, Hydrogen Reduction, and CO Oxidation Activities

Youngku Sohn 한국진공학회(ASCT) 2019 Applied Science and Convergence Technology Vol.28 No.3

The introduction of guest metal ions significantly change the nature of bare support materials. In this study lanthanide, Ln, (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) ions were loaded into a cubic phase CeO₂ support by a hydrothermal method. Their fundamental characteristics were examined by scanning electron microscopy, transmission electron microscopy, optical microscopy, X-ray diffraction crystallography, and Raman spectroscopy. Their CO oxidation performances temperature were measured by temperature-programmed reaction mass spectrometry. It was found that the fundamental natures of the Ln-loaded catalysts were all dependent on the ionic radii of guest lanthanide metal ions. Higher CO oxidation activities were obtained for lanthanide metal ions with ionic radii closer to that of the host Ce<SUP>4+</SUP> ion. The present results highlight that defects, particles sizes and surface active sites were affected from the matching of the host and guest-guest ionic radii.

Thermal and Photochemistry of Methyl Iodide on Ice Film Grown on Cu(111)

Youngku Sohn,John M. White 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.7

Thermal and photochemistry of methyl iodide (CH3I) adsorbed on D2O ice film on Cu(111) at 100 K were studied using temperature-programmed desorption (TPD) time-of-flight mass spectrometry (TOF-MS), X-ray and ultraviolet photoelectron spectroscopies. On the basis of TPD, multilayer and monolayer CH3I molecules desorb from D2O ice layer at 120 and 130 K, respectively. Photo-irradiation at 100 K exhibits dramatic changes in the TPD and I 3d5/2 XPS of CH3I on ice film, due to a dramatic dissociation of CH3I. The dissociation is likely activated by solvated electrons transferred from the metal substrate during photo-irradiation. No other photo-initiated reaction products were found within our instrumental detection limit. During photo-irradiation, the CH3I, CH3 and I could be trapped (or solvated) in ice film by rearrangement (and self-diffusion) of water molecules. A newly appeared parent molecular desorption peak at 145 K is attributed to trapped CH3I. In addition, the CH3 and I may diffuse through ice and chemisorb on Cu(111), indicated by TPD and I 3d5/2 XPS taken with photo-irradiation time, respectively. No molecular ejection was found during photo-irradiation at 100 K. The work functions for CH3I/Cu(111), D2O/Cu (111) and CH3I/D2O/Cu(111) were all measured to be about 3.9 eV, 1.0 eV downward shift from that of clean Cu(111).

Recent progress and perspectives in the photocatalytic CO₂ reduction of Ti-oxide-based nanomaterials

Sohn, Youngku,Huang, Weixin,Taghipour, Fariborz Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.396 No.-

<P><B>Abstract</B></P> <P>The conversion of CO<SUB>2</SUB> with H<SUB>2</SUB>O to valuable chemicals and fuels is a new solution to current environmental and energy problems, and the high energy barrier of these reactions can be overcome by the input of solar and electrical energy. However, the reduction efficiencies and selectivities of these reactions are insufficient for practical use, and significant effort and strategy are required to overcome the many obstacles preventing the large-scale application of photocatalytic CO<SUB>2</SUB> reduction. This article reviews recent progress in CO<SUB>2</SUB> reduction using titanium oxide-based materials and various strategic factors for increasing photocatalytic efficiency. This article also highlights non-titanium-oxide catalysts, the photoelectrocatalytic reduction of CO<SUB>2</SUB>, and other recent review articles concerning the recycling of CO<SUB>2</SUB> to value-added carbon compounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Conversion of stable CO<SUB>2</SUB> with H<SUB>2</SUB>O to valuable chemicals and fuels. </LI> <LI> Recent progress in CO<SUB>2</SUB> reduction over developed Ti-oxide-based materials. </LI> <LI> Various strategic factors for increasing the photocatalytic efficiency. </LI> <LI> Non Ti-oxide catalysts and photo-electrocatalytic reduction of CO<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Adsorption and Photocatalytic Performances of BiOI Nanostructures for Methyl Orange and Rhodamine B

Yohan Park,Youngku Sohn 한국진공학회 2013 한국진공학회 학술발표회초록집 Vol.2013 No.2

One-Dimensional Eu(III) and Tb(III)-Doped Gd Oxide Nanorods

Wonjoo Kim,Youngku Sohn 한국진공학회 2013 한국진공학회 학술발표회초록집 Vol.2013 No.2

Synergy of Low-Energy {101} and High-Energy {001} TiO₂ Crystal Facets for Enhanced Photocatalysis

Roy, Nitish,Sohn, Youngku,Pradhan, Debabrata American Chemical Society 2013 ACS NANO Vol.7 No.3

<P>Controlled crystal growth determines the shape, size, and exposed facets of a crystal, which usually has different surface physicochemical properties. Herein we report the size and facet control synthesis of anatase TiO<SUB>2</SUB> nanocrystals (NCs). The exposed facets are found to play a crucial role in the photocatalytic activity of TiO<SUB>2</SUB> NCs. This is due to the known preferential flow of photogenerated carriers to the specific facets. Although, in recent years, the main focus has been on increasing the surface area of high-energy exposed facets such as {001} and {100} to improve the photocatalytic activity, here we demonstrate that the presence of both the high-energy {001} oxidative and low-energy {101} reductive facets in an optimum ratio is necessary to reduce the charge recombination and thereby enhance photocatalytic activity of TiO<SUB>2</SUB> NCs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-3/nn305877v/production/images/medium/nn-2012-05877v_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn305877v'>ACS Electronic Supporting Info</A></P>

Green Synthesis of Anatase TiO₂ Nanocrystals with Diverse Shapes and their Exposed Facets-Dependent Photoredox Activity

Roy, Nitish,Park, Yohan,Sohn, Youngku,Leung, Kam Tong,Pradhan, Debabrata American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.19

<P>The exposed facets of a crystal are known to be one of the key factors to its physical, chemical and electronic properties. Herein, we demonstrate the role of amines on the controlled synthesis of TiO<SUB>2</SUB> nanocrystals (NCs) with diverse shapes and different exposed facets. The chemical, physical and electronic properties of the as-synthesized TiO<SUB>2</SUB> NCs were evaluated and their photoredox activity was tested. It was found that the intrinsic photoredox activity of TiO<SUB>2</SUB> NCs can be enhanced by controlling the chemical environment of the surface, i.e.; through morphology evolution. In particular, the rod shape TiO<SUB>2</SUB> NCs with ∼25% of {101} and ∼75% of {100}/{010} exposed facets show 3.7 and 3.1 times higher photocatalytic activity than that of commercial Degussa P25 TiO<SUB>2</SUB> toward the degradation of methyl orange and methylene blue, respectively. The higher activity of the rod shape TiO<SUB>2</SUB> NCs is ascribed to the facetsphilic nature of the photogenerated carriers within the NCs. The photocatalytic activity of TiO<SUB>2</SUB> NCs are found to be in the order of {101}+{100}/{010} (nanorods) > {101}+{001}+{100}/{010} (nanocuboids and nanocapsules) > {101} (nanoellipsoids) > {001} (nanosheets) providing the direct evidence of exposed facets-depended photocatalytic activity.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-19/am504084p/production/images/medium/am-2014-04084p_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am504084p'>ACS Electronic Supporting Info</A></P>

Interfacial nature of Ag nanoparticles supported on TiO2 photocatalysts

Kang, Jun-Gill,Sohn, Youngku Springer-Verlag 2012 JOURNAL OF MATERIALS SCIENCE - Vol.47 No.2

Reflective color display using thermochromic pigments

Heo, Kyong Chan,Sohn, Youngku,Yi, Jonghoon,Kwon, Jin Hyuk,Son, Phil Kook,Gwag, Jin Seog The Optical Society 2012 Applied Optics Vol.51 No.18

<P>A reflective thermochromic display fabricated by a very simple method using three kinds of thermochromic pigments is produced and its thermo-optical characteristics are investigated. The display exhibits maximum red, green, and blue reflectances of 38%, 30%, and 35%, respectively. The reflective display cell shows continuous gray color with changing temperature, which is crucial for multicolor displays. It also shows an excellent viewing angle above 80° without any of the additional optical components that are required in liquid crystal displays. We expect that this display technology will be used for outdoor billboard information display applications.</P>

Room temperature electroless Ni-coating on boron particles: Physicochemical and oxidation-resistance properties

P.R. Deshmukh,Youngku Sohn,Weon Gyu Shin 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.91 No.-

Ni nanoparticles were coated on irregularly shaped micron sized boron particles by facile electroless Nidepositionmethod. Four kinds of Ni-coated boron particles were prepared using four different simplepaths during the electroless deposition process: no rinsing and no drying (Path A), only drying (Path B),both rinsing and drying (Path C), and only rinsing (Path D). Surface morphology confirmed the Ninanoparticlescoating on the surface of boron particles. The size of the Ni nanoparticles varied between 10and 120 nm with respect to the chosen paths used for preparation. The Ni nanoparticle's size was alsostudied using TEM and found to be consistent with the surface morphology results. XRD measurement ofthe Ni-coated boron particles showed the formation of crystalline Ni nanoparticles. EDAX and XPS resultsshowed the presence of the primary B and Ni elements in the obtained samples. Thermogravimetricanalysis conducted in air atmosphere found the boron particles had enhanced oxidation resistance afterthe coating of Ni nanoparticles. The Ni-coated boron particles showed a shift in exothermic peak to alower temperature and higher heat evolution than the pure boron, recommending the use of Ni-coatedboron particles in solid fuel in missile/rocket engines, and high temperature applications.