The dependence of hydrogen storage properties on the sizes of Pd nanoparticles prepared by a solution-reduction method
JAPANESE JOURNAL OF APPLIED PHYSICS
Authors: Ozawa, Masakuni; Todoroki, Tatumi; Kato, Hitoshi; Hattori, Masatomo
Abstract
We performed a size-controlled synthesis of Pd nanoparticles (NPs) by changing the initial concentration of Pd in a solution. The correlation between the hydrogen absorption isotherm (denoted as pressure-composition-temperature (PCT)) and the Pd particle size was examined by focusing on sizes between 5 and 10 nm in diameter. The PCT curves confirmed the characteristics of Pd NPs less than 10 nm in diameter, which were different from those of bulk Pd and strongly dependent on the crystallite size. The hydrogen isotherms of the 6.5 and 6.8 nm Pd NPs showed that the final amount of hydrogen was 0.3 at 0.1 MPa and their plateaus were shorter, with a steeper gradient. The hydrogen isotherm of the 5.5 nm NP showed no plateau and realized the nanoscale-regime phenomenon. For the hydrogen absorption of Pd, based on our experimental findings, the size-dependent tipping point between the bulk and NP regimes seems to lie at about 6 nm in diameter.
Photoelectrochemical and photocatalytic detoxification of Cr(VI) to Cr(III) over terpyridine-derivatized Au nanoparticles on carbon paper and indium-tin-oxide electrodes
CHEMICAL ENGINEERING JOURNAL
Authors: Yi, Jae Moon; Kim, Tae Jun; Park, So Jeong; Hong, Sung-Min; Kang, Jun-Gill; Rhee, Choong Kyun; Kim, Jongwon; Sohn, Youngku
Abstract
Detoxification of hexavalent chromium (Cr(VI)) in the environment and development of corresponding new materials and detoxification protocols have actively been studied and applied. Herein, 2,2':6',2 ''-terpyridine-4'-thiol (STpy) was functionalized on Au nanoparticle (NP)-loaded carbon paper (CP) and indium-fin-oxide (ITO) electrodes (CP-AuNP and ITO-AuNP, respectively), and the photoelectrochemical (PEC) and photocatalytic detoxification of Cr(VI) using the resulting electrodes was investigated by cyclic voltammetry. Density functional theory at the B3LYP/6-31G level was used for geometry optimization, and the electronic energy state calculation was conducted at the TD-SCF/DFT/B3LYP level. For bare CP, ITO, and STpy-modified AuNP electrodes, the reduction potentials of Cr(VI) were around +0.3, -0.2 V, and +0.5 V (vs. Ag/AgCl), respectively. The PEC and photocatalytic Cr(VI) reduction performance of CP-AuNP was significantly improved upon STpy functionalization. Thus, these newly developed functionalized systems can provide very useful information for further improving the detoxification performances for various hazardous metals.
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