• 공업화학
• /
• 제31권6호
• /
• pp.674-678
• /
• 2020

본 연구에서는 상온 조건에서 추가적인 에너지원 없이 H2 산화가 가능한 Pd/TiO2 촉매를 제조하였고, 지지체인 TiO2의 비표면적은 Pd/TiO2 촉매의 H2 산화 반응 성능과 비례하지는 않은 것을 확인하였다. 또한 촉매의 물성 변화에 의한 성능 영향 평가를 위하여 La2O3를 Pd/TiO2 촉매에 첨가하였다. La2O3를 TiO2에 함량별로 첨가하여 Pd/La2O3-TiO2를 제조하였고, CO chemisorption 분석을 진행하였다. Pd/TiO2(G) 촉매의 전환율(14% at 0.5% H2)과 비교하여 Pd/La2O3-TiO2 촉매가 74% 전환율로 5배 이상의 성능 증진이 나타났다. Pd/La2O3-TiO2 촉매는 활성금속인 Pd의 metal dispersion이 클수록 H2 산화반응에 유리한 것으로 분석되었다. 하지만 첨가되는 La2O3가 10%를 초과하게 되면 촉매 성능이 다시 감소하는 것을 알 수 있었다. 마지막으로 Pd/La2O3-TiO2 촉매의 물성이 지배적인 영향을 미치는 것은 주입되는 H2가 0.3~0.5% 농도 조건까지이며, 1% 이상의 H2 농도부터는 물질전달이 촉매 반응속도를 지배하는 것으로 판단된다.

• 센서학회지
• /
• 제23권3호
• /
• pp.207-210
• /
• 2014

$TiO_2$ oxide semiconductor is being widely studied in various applications such as photocatalyst and photosensor. Pd/$TiO_2$ gas sensor is mainly used to detect $H_2$, CO and ethanol. This study focus on increasing hydrogen detection ability of Pd/$TiO_2$ in room temperature through Al-doping. Pd/$TiO_2$ was fabricated by the hydrothermal method. Contacting to Aluminum (Al) foil led to Al doping effect in Pd/$TiO_2$ by thermal diffusion and enhanced hydrogen sensing response. $TiO_2$ nanoparticles were sized at ~30 nm of diameter from scanning electron microscope (SEM) and maintained anatase crystal structure after Al doping from X-ray diffraction analysis. Presence of Al in $TiO_2$ was confirmed by X-ray photoelectron spectroscopy at 73 eV. SEM-energy dispersive spectroscopy measurement also confirmed 2 wt% Al in Pd/$TiO_2$ bulk. The gas sensing test was performed with $O_2$, $N_2$ and $H_2$ gas ambient. Pd/Al-doped $TiO_2$ did not response $O_2$ and $N_2$ gas in vacuum except $H_2$. Finally, the normalized resistance ratio ($R_{H2on}/R_{H2off}$) of Pd/Al-doped $TiO_2$ increases about 80% compared to Pd/$TiO_2$.

• 한국자기학회지
• /
• 제23권1호
• /
• pp.7-11
• /
• 2013

본 연구에서는 $TiO_2$/Co/Pd 구조의 다층박막을 마그네트론 스퍼터링으로 GaAs(100), MgO(100), MgO(111), Si(100), glass와 같은 다양한 종류의 기판에 대해 제작하여 수직 자기 이방성에 대해서 연구하였다. 산소 분압 등의 $TiO_2$ 층의 증착 조건과 기판의 종류에 따른 Co/Pd 층의 수직 자기 이방성을 측정하였다. 그 결과, $TiO_2$ 층이 5 nm 이하 일 때는 기판의 종류에 영향을 받지만, 그 이상의 두께에 대해서는 MgO(111)을 제외한 기판의 영향이 크지 않음을 확인하였고, 이는 $TiO_2$ 씨앗층의 성장조건과 계면의 거칠기, 결정방향 등과 관련이 있음을 발견하였다.

• Bulletin of the Korean Chemical Society
• /
• 제30권5호
• /
• pp.1047-1053
• /
• 2009

The future use of hydrogen as an energy source is expected to increase on account of its environmentally friendliness. In order to enhance the production of hydrogen, Pd ions (0.01, 0.05, 0.1, and 0.5 mol%) were incorporated $TiO_2$ (Pd-$TiO_2$) and used as a photocatalyst. The UV-visible absorbance decreased with increasing level of palladium incorporation without a wavelength shift. Although all the absorption plots showed excitation characteristics, there was an asymmetric tail observed towards a higher wavelength caused by scattering. However, the intensity of the photoluminescence (PL) curves of Pd-$TiO_2$ was smaller, with the smallest case being observed at 0.1 and 0.5 mol% Pd-$TiO_2$, which was attributedto recombination between the excited electrons and holes. Based on these optical characteristics, the evolution of $H_2$ from methanol/water (1:1) photo-splitting over Pd-$TiO_2$ in the liquid system was enhanced, compared with that over pure $TiO_2$. In particular, 2.4 mL of $H_2$ gas was produced after 8 h when 0.5 g of a 1.0 mol% Pd-$TiO_2$ catalyst was used. $H_2$ was stably evolved even after 28 h without catalytic deactivation, and the amount of $H_2$ produced reached 14.5 mL after 28 h. This is in contrast to the case of the Pd 0.1 mol% impregnated $TiO_2$ of $H_2$ evolution of 17.5 mL due to the more decreasedelectron-hole recombination.

• 대한의용생체공학회:의공학회지
• /
• 제25권5호
• /
• pp.383-389
• /
• 2004

본 연구에서는 치과용 티타늄(CP-Ti)과 Ti-25wt%Pd를 인산염계 실리카$.$알루미나 주형재로 주조 후 SEM/EDS, XRD, XPS를 이용하여 주조시 생성되는 표면반응생성물을 조사하였다. Ti-25wt%Pd는 CP-Ti에 비하여 융점이 현저이 감소하여 주조체의 표면반응이 상대적으로 적게 발생하였다. 또한 인산염계 실리카$.$알루미나 주형재를 소성한 결과 주형재는 $SiO_2$, $Al_2$ $O_3$, P$_2$ $O_{5}$, $Mg_3$(P $O_4$)$_2$, AlP $O_4$, $Mg_2$ $SiO_4$, MgAl$_2$ $O_4$의 성분들로 구성되어 있었으며, 표면반응생성물은 CP-Ti 주조체의 경우 $Ti_{5}$Si$_3$ 와 Ti $O_2$로, Ti-25wt%Pd 주조체의 경우 Ti $O_2$ 와 $SiO_{x}$ 로 구성되어 있었다.

• Bulletin of the Korean Chemical Society
• /
• 제22권1호
• /
• pp.30-36
• /
• 2001

The crystal structures of fully dehydrated $Pd^{2+}$ - and $TI^{+}$ -exchanged zeolite X, $Pd_{18}TI_{56}Si_{100}Al_{92}O_{384}(Pd_{18}TI_{50-}X$, a = $24.935(4)\AA$ and $Pd_{21}TI_{50}Si_{100}Al_{92}O_{384}(Pd_{21}TI_{50-}X$ a = $24.914(4)\AA)$, have been determined by single-crystal X-ray diffraction methods in the cubic space group Fd3 at $21(1)^{\circ}C.$ The crystals were prepared using an exchange solution that had a $Pd(NH_3)_4Cl_2\;:TINO_3$ mole ratio of 50 : 1 and 200 : 1, respectively, with a total concentration of 0.05M for 4 days. After dehydration at $360^{\circ}C$ and 2 ${\times}$$10^{-6}$ Torr in flowing oxygen for 2 days, the crystals were evacuated at $21(1)^{\circ}C$ for 2 hours. They were refined to the final error indices $R_1$ = 0.045 and $R_2$ = 0.038 with 344 reflections for $Pd_{18}Tl_{56-}X$, and $R_1$ = 0.043 and $R_2$ = 0.045 with 280 reflections for $Pd_{21}Tl_{50-}X$; I > $3\sigma(I).$ In the structure of dehydrated $Pd_{18}Tl_{56-}X$, eighteen $Pd^{2+}$ ions and fourteen $TI^{+}$ ions are located at site I'. About twenty-seven $TI^{+}$ ions occupy site II recessed $1.74\AA$ into a supercage from the plane of three oxygens. The remaining fifteen $TI^{+}$ ions are distributed over two non-equivalent III' sites, with occupancies of 11 and 4, respectively. In the structure of $Pd_{21}Tl_{50-}X$, twenty $Pd^{2+}$ and ten $TI^{+}$ ions occupy site I', and one $Pd^{2+}$ ion is at site I. About twenty-three $TI^{+}$ ions occupy site II, and the remaining seventeen $TI^{+}$ ions are distributed over two different III' sites. $Pd^{2+}$ ions show a limit of exchange (ca. 39% and 46%), though their concentration of exchange was much higher than that of $TI^{+}$ ions. $Pd^{2+}$ ions tend to occupy site I', where they fit the double six-ring plane as nearly ideal trigonal planar. $TI^{+}$ ions fill the remaining I' sites, then occupy site II and two different III' sites. The two crystal structures show that approximately two and one-half I' sites per sodalite cage may be occupied by $Pd^{2+}$ ions. The remaining I' sites are occupied by $TI^{+}$ ions with Tl-O bond distance that is shorter than the sum of their ionic radii. The electrostatic repulsion between two large $TI^{+}$ ions and between $TI^{+}$ and $Pd^{2+}$ ions in the same $\beta-cage$ pushes each other to the charged six-ring planes. It causes the Tl-O bond to have some covalent character. However, $TI^{+}$ ions at site II form ionic bonds with three oxygens because the super-cage has the available space to obtain the reliable ionic bonds.

• 공업화학
• /
• 제28권5호
• /
• pp.547-553
• /
• 2017

본 연구는 $TiO_2$ 골격에 Pd을 삽입시켰을 때 나타나는 광 촉매 성능의 차이에 초점을 두고, $TiO_2$와 x mol% $Pd-TiO_2$(x = 0.25, 0.5, 0.75 그리고 1.0)의 5가지 촉매를 제안하였다. 전형적인 졸-겔 방법을 사용하여 촉매를 합성하고 각 촉매의 페놀 광 분해 성능을 평가하였다. XRD, TEM, SEM/EDS, UV/Vis 분광법, 광 발광 분광법 등을 이용하여 촉매의 물리화학적 특성을 확인하였고, 광 발광 분광법 및 광 전류 측정으로 광학적 특성을 확인하였다. Pd 이온을 첨가하면 촉매의 밴드 갭이 감소하고, 광 생성된 전자와 정공 사이의 전하 분리가 쉽게 발생한다. 결과적으로, 0.75 mol% $Pd-TiO_2$ 촉매상의 페놀 광 분해 성능은 순수한 $TiO_2$보다 3배 더 높았는데, 이는 광 촉매 반응 중에 Pd 이온이 전자캡쳐 역할을 하여 일어난 결과로 여겨진다.

• 한국재료학회지
• /
• 제32권1호
• /
• pp.14-22
• /
• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• 한국세라믹학회지
• /
• 제50권4호
• /
• pp.251-256
• /
• 2013

Multiwalled carbon nanotubes (MWCNTs) modified with Pd and $TiO_2$ composite catalysts were synthesized by the sol-gel method followed by solvothermal treatment at low temperature. The chemical composition and surface structure were characterized by X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Photocatalytic recycle degradation experiments were carried out under both UV and visible light irradiation in the presence of MWCNT/$TiO_2$ and Pd-MWCNT/$TiO_2$ composites. As expected, the nanosized Pd-MWCNT/$TiO_2$ photocatalysts had enhanced activity over the non Pd treated MWCNT/$TiO_2$ material in the degradation of a rhodamine B (Rh.B) solution. An increase in photocatalytic activity was observed and attributed to an increase in the photo-absorption effect by MWCNTs and the cooperative effect of Pd and $TiO_2$ nanoparticles. According to the recycled results, the as-prepared Pd-MWCNT/$TiO_2$ sample had a good effect on it.

• Bulletin of the Korean Chemical Society
• /
• 제34권8호
• /
• pp.2461-2465
• /
• 2013

Pd-$Ce/{\gamma}-Al_2O_3-TiO_2$ catalysts were prepared by combined sol-gel and impregnation methods. Transmission electron microscopy, X-ray diffraction, $H_2$-temperature-programmed reduction, $O_2$-temperature-programmed desorption, and ethanol oxidation experiments were conducted to determine the properties of the catalysts. Addition of an optimal amount of Ce improved the performance of the $Pd/{\gamma}-Al_2O_3-TiO_2$ catalyst in promoting the complete oxidation of ethanol. The catalyst with 1% Ce exhibited the highest activity, and catalyzed complete oxidation of ethanol at $175^{\circ}C$; its selectivity to $CO_2$ reached 87%. Characterization results show that addition of appropriate amount of Ce could enrich the PdO species, and weaken the Pd-O bonds, thus enhancing oxidation ability of the catalyst. Meanwhile, the introduction of $CeO_2$ could make PdO better dispersed on ${\gamma}-Al_2O_3-TiO_2$, which is beneficial for the improvement of the catalytic oxidation activity.