WO₃ 첨가에 의한 TiO₂계 SCR 촉매의 상전이 및 입자성장이 고온안정성에 미치는 영향

윤상현,김장훈,신병길,박삼식,신동우,이희수,Yoon, Sang-Hyeon,Kim, Jang-Hoon,Shin, Byeong-Kil,Park, Sam-Sik,Shin, Dong-Woo,Lee, Hee-Soo 한국결정성장학회 2011 韓國結晶成長學會誌 Vol.21 No.4

$WO_3$ 첨가가 $TiO_2$계 SCR 촉매의 고온안정성에 미치는 영향을 구조적, 형상학적 분석을 통해 규명하였다. 순수한 $TiO_2$시편과 10 wt%의 $WO_3$를 첨가한 $WO_3-TiO_2$ 시편을 제조하여 $800^{\circ}C$에서 5시간 동안 열적 스트레스를 인가하였다. FT-IR을 이용하여 촉매의 산점 변화를 확언한 결과 $WO_3-TiO_2$ 시편의 경우가 순수한 $TiO_2$ 시편에 비해 열적 열화로 인한 산점의 감소가 상대적으로 적었다. 반면 $WO_3-TiO_2$ 와 $TiO_2$의 anatase에 서 rutile로의 상전이 정도는 각각 28.4%와 22.9%로 오히려 $WO_3-TiO_2$ 시편에서 rutile 상이 더 많이 증가한 것을 확인하였다. 형상학적 분석 결과 $WO_3-TiO_2$ 시편은 고온에서 $TiO_2$에 고용되어 있던 amorphous 상태의 $WO_3$가 $TiO_2$ 입자 표면에 석출되며 결정화가 일어나게 되고 이로 인해 촉매의 입자성장을 억제함을 확인하였다. 따라서 SCR용 $TiO_2$ 촉매에 첨가된 $WO_3$는 anatase에서 rutile로의 상전이를 촉진시켜 고온에서의 촉매 활성을 저하시킬 수 있지만, 입성장 억제에 대한 영향이 커 결과적으로 고온안정성을 향상시킴을 확인하였다. Thermal stability of the $TiO_2$ SCR catalyst with W03 loading was investigated in terms of structural and morphological analyses. The $TiO_2$ catalysts with 10 w% $WO_3$ content and without $WO_3$ were prepared. which were heat-treated at $800^{\circ}C$ for 5 h. It was found that the catalytic acidity was decreased by thermal degradation in the $WO_3-TiO_2$ specimen that relatively less than the $TiO_2$ specimen from FT-IR analysis. The phase transition of the $TiO_2$ catalyst from anatase to rutile was increased by heal-treatment, and the percentage of the rutile phase was 28.4 % in the $WO_3-TiO_2$ and 22.9 % in the $TiO_2$. A shell region of $WO_3$ distinguished from a $TiO_2$ particle was also observed in the grain boundary region, and the $WO_3$ led to the suppression of grain growth. It could be confirmed that the suppression of grain growth can contribute to the improvement of catalytic properties for thermal stability more than the increase of anatase-rutile phase transformation which cause the reduction of the catalytic activity in the $TiO_2$ SCR catalyst by the presence of $WO_3$.

리튬이온커패시터용 Polyaniline/WO₃ 음극 제조 및 이의 광 조사에 따른 전기화학적 특성 변화

박이슬 ( Yiseul Park ) 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.6

본 연구에서는 리튬이온커패시터의 음극으로 polyaniline (PANI)/WO₃ 전극을 제조하고, 이의 전기화학적 특성을 측정, 분석하였다. WO₃ 전극 표면에 PANI를 전기화학적으로 담지 하였을 때 PANI의 용량이 더해져 WO₃ 전극보다 충, 방전 용량이 향상되었다. 한편, 충, 방전 시 태양광을 조사하여 충, 방전 용량과 쿨롱 효율(coulombic efficiency)에 빛 조사가 미치는 영향을 파악하였다. WO₃ 전극과 PANI/WO₃ 전극에 태양광을 조사하였을 때, 두 전극의 충, 방전 용량과 쿨롱 효율은 태양광을 조사하지 않았을 때보다 증가하였다. 이는 WO₃가 빛 조사에 의해 광전자를 생성하여 전극의 전기화학적 특성에 영향을 주기 때문으로 해석되며, PANI/WO₃의 경우 PANI 또한 빛에 의해 여기 될 수 있어 전극의 특성이 변하게 된다. 빛 조사에 의해 추가로 생성된 광전자가 Li⁺ 이온의 삽입(intercalation)에 사용되어 용량을 증가시킬 수 있을 뿐 아니라, 전극의 전도성을 높여 쿨롱 효율을 향상 시키는 것으로 여겨진다. PANI/WO₃는 충, 방전을 반복하여 진행하게 되면 PANI의 불안정성으로 인해 용량이 점차 감소되게 되지만, 빛 조사 시에는 생성된 광전자와 정공으로 인한 산화-환원 반응에 의해 PANI의 안정성이 크게 향상되어 충, 방전 용량의 감소없이 안정적으로 유지되었다. In this study, polyaniline (PANI)/WO₃ electrode was prepared as an anode of a lithium ion capacitor, and its electrochemical characteristics were measured and analyzed. When PANI was electrochemically deposited on the surface of WO₃ electrode, the capacity of PANI/WO₃ was improved with increase of the deposited amounts of PANI. Furthermore, the effect of light irradiation on capacity and coulombic efficiency was examined by irradiating sunlight during charging and discharging. When the light was irradiated to the WO₃ electrode and the PANI/WO₃ electrode, those capacities and coulombic efficiencies were increased compared to that measured under the dark condition. It is attributed to the photocatalytic property of WO₃ that can generate photoelectrons by light irradiation. In PANI/WO₃ electrode, PANI also can be excited under the light irradiation with affecting the electrochemical property of electrode. The photoelectrons improve the capacity by participating in the intercalation of Li⁺ ions, and also improve the coulombic efficiency by facilitating electrons’ transport. Under the dark condition, the capacity of PANI/WO₃ was gradually reduced with increase of cycles due to a poor stability of PANI. However, the stability of PANI was significantly improved by the light irradiation, which is attributed to the oxidation-reduction reaction originated from the photogenerated electrons and holes in PANI/WO₃.

WO₃ nanofibrous backbone scaffolds for enhanced optical absorbance and charge transport in metal oxide (Fe₂O₃, BiVO₄) semiconductor photoanodes towards solar fuel generation

Choi, Junghyun,Song, Taeseup,Kwon, Jiseok,Lee, Sangkyu,Han, Hyungkyu,Roy, Nitish,Terashima, Chiaki,Fujishima, Akira,Paik, Ungyu,Pitchaimuthu, Sudhagar Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.447 No.-

<P><B>Abstract</B></P> <P>Producing clean fuel (O<SUB>2</SUB> and H<SUB>2</SUB>) using semiconductors through solar driven water splitting process has been considered as a promising technology to mitigate the existing environmental issues. Unlike the conventional single photoabsorbers, heterostructured semiconductors exhibit the merits of improved solar light photon harvesting and rapid charge separation, which are anticipated to result in high quantum yield of solar fuel generation in photoelectrochemical (PEC) cells. In this report, we demonstrate the electrospun derived WO<SUB>3</SUB> backbone fibrous channel as heteropartner to the primary photoabsorber (Fe<SUB>2</SUB>O<SUB>3</SUB> and BiVO<SUB>4</SUB>) for promoting the electron transport from charge injection point to charge collector as well as photoholes to the electrolyte. We examine structure, optical, photoelectrochemical and charge transfer property of Fe<SUB>2</SUB>O<SUB>3</SUB>/WO<SUB>3</SUB> and BiVO<SUB>4</SUB>/WO<SUB>3</SUB> electrodes. These results were compared with directly coated Fe<SUB>2</SUB>O<SUB>3</SUB> and BiVO<SUB>4</SUB> photoabsorber onto conducting substrate without WO<SUB>3</SUB> backbone. The optical results showed that the absorbance and visible light activity of Fe<SUB>2</SUB>O<SUB>3</SUB> and BiVO<SUB>4</SUB> is significantly improved by WO<SUB>3</SUB> backbone fibers due to high amount of photo absorber loading. In addition, one dimensional (1-D) WO<SUB>3</SUB> fibers beneficially enhance the optical path length to the photoanode through light scattering mechanism. The electrochemical impedance analysis exhibits WO<SUB>3</SUB> nanofiber backbone reduces charge transfer resistance at Fe<SUB>2</SUB>O<SUB>3</SUB> and BiVO<SUB>4</SUB> by rapid charge collection and charge separation compare to backbone-free Fe<SUB>2</SUB>O<SUB>3</SUB> and BiVO<SUB>4</SUB>. As a result, Fe<SUB>2</SUB>O<SUB>3</SUB>/WO<SUB>3</SUB> and BiVO<SUB>4</SUB>/WO<SUB>3</SUB> fibrous hetero interface structures showed fourfold higher photocurrent generation from PEC cell.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sol-gel spin coated Fe<SUB>2</SUB>O<SUB>3</SUB> and BiVO<SUB>4</SUB> thin films onto WO<SUB>3</SUB> fiber is demonstrated. </LI> <LI> Light absorbance promoted at Fe<SUB>2</SUB>O<SUB>3</SUB> and BiVO<SUB>4</SUB> by introducing WO<SUB>3</SUB> nanofibrous. </LI> <LI> Charge transfer at Fe<SUB>2</SUB>O<SUB>3</SUB>, BiVO<SUB>4</SUB> photoanode/electrolyte interfaces is examined. </LI> <LI> Role of 1-D WO<SUB>3</SUB> fibrous backbone scaffold in solar fuel generation is explored. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Highly efficient AgVO3/WO3 photocatalyst n-n heterojunction toward visible-light induced degradation antibiotic

Khalid A. Alzahrani,Adel A. Ismail 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.124 No.-

In the present work, WO3 NPs were fabricated using a facile hydrothermal method assisted bypolyvinylpyrrolidone (PVP) for the first time, and AgVO3 with different weight percentages (3%, 6%, 9%and 12%) was uniformly distributed on the surface of mesoporous WO3 by impregnation - calcinationprocesses to construct n-n heterojunction AgVO3/WO3 nanocomposites. The obtained AgVO3/WO3nanocomposites were utilized for the effective Ciprofloxacin (CIP) degradation during visible illumination. The XRD and TEM investigations verified the formation of AgVO3 and WO3 in a monoclinic crystalstructure with a particle size of 40 nm. XPS and TEM measurements evidenced the existence of Agoand Ag+ in the heterostructure AgVO3/WO3 system. 9%AgVO3/WO3 nanocomposite exhibited larger photocatalyticperformance, i.e., 100% with 120 min of illumination, than the other nanocomposite photocatalysts. The apparent rate constant of 9% AgVO3/WO3 nanocomposite (0.0162 min1) was enhanced 18times greater than the WO3 NPs (0.0009 min1). The efficient photocatalytic performance could correlatewith the close contact between AgVO3 and WO3 NPs, which enhanced the visible light absorption andefficacious separation of the carriers during degradation reactions. The AgVO3/WO3 nanocompositeobeyed the S-scheme mechanism for charge transfer to achieve promising redox abilities in bothAgVO3 and WO3. The optimized 9% AgVO3/WO3 photocatalyst showed high reusability and photostabilityfor five consecutive runs without loss its efficiency. This study provides a new mechanism for addressinghighly effective nanocomposites with excellent photocatalytic ability that exhibit practical applicationsin the environmental remediation of antibiotics.

Cr₂O₃ nanoparticle-functionalized WO₃ nanorods for ethanol gas sensors

Choi, Seungbok,Bonyani, Maryam,Sun, Gun-Joo,Lee, Jae Kyung,Hyun, Soong Keun,Lee, Chongmu Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.432 No.2

<P><B>Abstract</B></P> <P>Pristine WO<SUB>3</SUB> nanorods and Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods were synthesized by the thermal evaporation of WO<SUB>3</SUB> powder in an oxidizing atmosphere, followed by spin-coating of the nanowires with Cr<SUB>2</SUB>O<SUB>3</SUB> nanoparticles and thermal annealing in an oxidizing atmosphere. Scanning electron microscopy was used to examine the morphological features and X-ray diffraction was used to study the crystallinity and phase formation of the synthesized nanorods. Gas sensing tests were performed at different temperatures in the presence of test gases (ethanol, acetone, CO, benzene and toluene). The Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor showed a stronger response to these gases relative to the pristine WO<SUB>3</SUB> nanorod sensor. In particular, the response of the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor to 200ppm ethanol gas was 5.58, which is approximately 4.4 times higher that of the pristine WO<SUB>3</SUB> nanorods sensor. Furthermore, the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor had a shorter response and recovery time. The pristine WO<SUB>3</SUB> nanorods had no selectivity toward ethanol gas, whereas the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor showed good selectivity toward ethanol. The gas sensing mechanism of the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor toward ethanol is discussed in detail.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pristine WO<SUB>3</SUB> nanorods and Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods were synthesized. </LI> <LI> The Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorod sensor showed a stronger response to these gases than the pristine WO<SUB>3</SUB> nanorod sensor. </LI> <LI> The former sensor showed a shorter response and recovery time than the latter one. </LI> <LI> The Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor showed good selectivity toward ethanol. </LI> <LI> The underlying mechanisms for the enhanced sensing performance of the functionalized sensor are discussed in detail. </LI> </UL> </P>

Acetone Sensing of Multi-Networked WO3-NiO Core-Shell Nanorod Sensors

최승복,이재경,이우석,이충무,이완인 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.8

WO3-NiO core-shell nanorods were synthesized by thermal evaporation of a mixture of WO3 and graphite powders and immersion of the synthesized WO3 nanorods in an 20 mM of nickel(II) acetate tetrahydrate (Ni(OCOCH3)2·4H2O) solution followed by UV irradiation and annealing. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The sensing properties of pristine WO3 nanorod and WO3-NiO core-shell nanorod sensors toward acetone were examined. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The WO3-NiO core-shell nanorod sensor exhibited a stronger response to acetone gas and shorter response/recovery times than the pristine WO3 nanorod sensor. The pristine WO3 nanorods showed responses of approximately 1.36 to 200 ppm of CH3COCH3 at 300 C. On the other hand, the WO3-NiO core-shell nanorods showed responses of 4.4 to the same concentration of CH3COCH3 at the same temperature. The coreshell nanorods exhibited response and recovery times of 51 s and 59 s, respectively for 200 ppm of CH3COCH3. On the other hand, the pristine WO3 nanorods exhibited response and recovery times of 51 s and 59 s, respectively, for the same concentration of CH3COCH3. NiO coating enhanced the selectivity of the WO3 nanorods for acetone as well as the sensitivity of the WO3 nanorods. The underlying mechanism of the enhanced response of the WO3-NiO core-shell nanorod sensor is also discussed in detail.

텅스텐(W) 원료에 따른 WO₃/TiO₂ SCR 촉매의 제조 및 촉매능

이병우,이진희,Lee, Byeong Woo,Lee, Jin Hee 한국결정성장학회 2014 韓國結晶成長學會誌 Vol.24 No.5

Anatase $TiO_2$에 각기 다른 텅스텐(W) 함유원료와 제조방법을 적용하여 $WO_3$ 촉매가 첨가된 SCR(selective catalytic reduction)용 분말을 합성하였으며, W 촉매 첨가가 합성분말의 상합성 및 SCR 촉매능에 미치는 영향에 대해 연구하였다. 촉매의 지지체인 $TiO_2$는 침전법으로 anatase 상으로 합성되었으며, anatase에서 고온상인 rutile로의 상전이 온도는 $1200^{\circ}C$였으나, $WO_3$를 10 wt% 첨가할 경우 이 상전이 온도는 $900^{\circ}C$로 낮아졌다. 건식으로 $WO_3$ 분말을 직접 첨가하여 $WO_3(10wt%)/TiO_2$를 제조한 경우 $350^{\circ}C$에서 $NO_X$ 제거 촉매능이 최고점에 이르나 온도증가에 따라 그 효율이 상당히 감소하였다. 암모늄-메타-텅스테이트를 습식으로 첨가하여 제조한 경우, 보다 고온인 $450^{\circ}C$에서 촉매능이 최고점에 이르렀으며 온도에 따른 효율감소 폭도 적었다. 이와 같은 경향은 $WO_3$와 $V_2O_5$를 동시 첨가하여 제조한 $V_2O_5(5wt%)-WO_3(10wt%)/TiO_2$ 촉매에서도 나타났다. 즉, 암모늄-메타-텅스테이트를 습식으로 첨가한 경우, $WO_3$를 직접 첨가한 경우에 비해 넓은 온도범위($300^{\circ}C{\sim}500^{\circ}C$)에 걸쳐 90 %에 이상의 우수한 $NO_X$ 변환효율을 보였다. An investigation of the influence of $WO_3$ addition with different precursors and preparation methods on the phase formation and selective catalytic reduction (SCR) efficiency of anatase-$TiO_2$ powders has been carried out. An anatase-$TiO_2$ synthesized by precipitation process was used as a catalyst support. For $WO_3(10wt%)/TiO_2$, the W loading to the $TiO_2$ support led to the lower in anatase to rutile transition temperature to ${\sim}900^{\circ}C$ from $1200^{\circ}C$ of the $TiO_2$ support alone. In the case of $WO_3(10wt%)/TiO_2$ SCR powders obtained from a wet process with ammonium meta-tungstate (AMT) precursor, the highest $NO_X$ conversion efficiency was achieved at $450^{\circ}C$ remaining high efficiency at $500^{\circ}C$, while the same composition prepared from a dry process with $WO_3$ addition showed the lowered efficiency with temperature after reaching the efficiency maximum at $350^{\circ}C$. The same tendency has been found that the $V_2O_5(5wt%)-WO_3(10wt%)/TiO_2$ SCR powders obtained from the wet process with AMT precursor has shown the superior $NO_X$ conversion efficiency over 90 % in a wider temperature range of $300{\sim}500^{\circ}C$.

Thermal Evaporation 법에 의해 제조된 WO3 박막과 NiO-WO3 박막의 전기적 특성에 관한 연구

나은영,나동명,박진성 한국전기화학회 2005 한국전기화학회지 Vol.8 No.1

WO3 and NiO-WO3 thin films were deposited on a Si (100) substrate by using high vacuum thermal evaporation. The effects of various film thicknesses on the surface morphology WO3 and NiO-WO3 thin films were investigated. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the deposited films. The results suggest that as WO3 thin films became thick, certain size of grain grew. On the other hand, their grain grew up to a certain size(?) NiO-dopint to WO3 thin films inhibited the grain growth five times less than undoped WO3 thin films. doping This results show that NiO dope inhibited the grain growth of WO3 thin films. Also, the variation of doping growing NOx sensitivity(RNOx/Rair) to the thickness of WO3 and NiO-WO3 thin films were measured according to the thickness change of thin films and the working temperature of sensor in 5 ppm NOx gas. As a result, NiO-WO3 thin films showed more excellent properties than WO3 thin films for NOx sensitivity.

볼밀시간에 의한 WO₃:In₂O₃ 가스센서의 감응특성

신덕진,유윤식,박성현,유일,Shin, Deuck-Jin,Yu, Yun-Sik,Park, Sung-Hyun,Yu, Il 한국재료학회 2011 한국재료학회지 Vol.21 No.6

[ $WO_3$ ]powders were ball-milled with an alumina ball for 0-72 hours. $In_2O_3$ doped $WO_3$ was prepared by soaking ball-milled $WO_3$ in an $InCl_3$ solution. The mixed powder was annealed at $700^{\circ}C$ for 30 min in an air atmosphere. A paste for screen-printing the thick film was prepared by mixing the $WO_3$:In2O3 powders with ${\alpha}$-terpinol and glycerol. $In_2O_3$ doped $WO_3$ thick films were fabricated into a gas sensor by a screen-printing method on alumina substrates. The structural properties of the $WO_3$:$InO_3$ thick films were a monoclinic phase with a (002) dominant orientation. The particle size of the $WO_3$:$InO_3$ decreased with the ball-milling time. The sensing characteristics of the $In_2O_3$ doped $WO_3$ were investigated by measuring the electrical resistance of each sensor in the test-box. The highest sensitivity to 5 ppm $CH_4$ gas and 5 ppm $CH_3CH_2CH_3$ gas was observed in the ball-milled $WO_3$:$InO_3$ gas sensors at 48 hours. The response time of $WO_3$:$In_2O_3$ gas sensors was 7 seconds and recovery time was 9 seconds for the methane gas.

Insight into Charge Separation in WO₃/BiVO₄ Heterojunction for Solar Water Splitting

Chae, Sang Youn,Lee, Chang Soo,Jung, Hyejin,Joo, Oh-Shim,Min, Byoung Koun,Kim, Jong Hak,Hwang, Yun Jeong American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.23

<P>Recently, the WO3/BiVO4 heterojunction has shown promising, photoelectrochemical (PEC) water splitting activity based on its charge transfer and light absorption. capability, and notable enhancement of the photocurrent has been achieved via morphological modification of WO3. We developed a graft copolymer-assisted protocol for the synthesis of WO3 mesoporous thin films on a transparent conducting electrode, wherein the particle size, particle shape, and thickness of the WO3 layer were controlled by tuning the interactions in the polymer/sol gel hybrid. The PEC performance of the WO3 mesoporous photoanodes with various morphologies and the individual heterojunctions with BiVO4 (WO3/BiVQ(4)) were characterized by measuring the photocurrents in the absence/presence of hole scavengers using light absorption spectroscopy and intensity-modulated photocurrent spectroscopy. The morphology of the WO3 photoanode directly influenced the charge separation efficiency within the WO3 layer and concomitant charge collection efficiency in the WO3/BiVO4 heterojunction, showing the smaller sized nanosphere WO3 layer showed higher values than did the plate-like or rod-like one. Notably, we observed that photocurrent density of WO3/BiVO4 was not dependent on the thickness of WO3 film or its charge collection time, implying slow charge flow from BiVO4 to WO3 can be a crucial issue in determining the photocurrent, rather than the charge separation within the nanosphere WO3 layer.</P>