Structural color-tunable mesoporous bragg stack layers based on graft copolymer self-assembly for high-efficiency solid-state dye-sensitized solar cells

Lee, Chang Soo,Park, Jung Tae,Kim, Jong Hak Elsevier 2016 Journal of Power Sources Vol.324 No.-

<P><B>Abstract</B></P> <P>We present a facile fabrication route for structural color-tunable mesoporous Bragg stack (BS) layers based on the self-assembly of a cost-effective graft copolymer. The mesoporous BS layers are prepared through the alternating deposition of organized mesoporous-TiO<SUB>2</SUB> (OM-TiO<SUB>2</SUB>) and -SiO<SUB>2</SUB> (OM-SiO<SUB>2</SUB>) films on the non-conducting side of the counter electrode in dye-sensitized solar cells (DSSCs). The OM layers with controlled porosity, pore size, and refractive index are templated with amphiphilic graft copolymers consisting of poly(vinyl chloride) backbones and poly(oxyethylene methacrylate) side chains, <I>i.e.</I>, PVC-<I>g</I>-POEM. The morphology and properties of the structural color-tunable mesoporous BS-functionalized electrodes are characterized using energy filtered transmission electron microscopy (EF-TEM), field emission-scanning electron microscopy (FE-SEM), spectroscopic ellipsometry, and reflectance spectroscopy. The solid-state DSSCs (ssDSSCs) based on a structural color-tunable mesoporous BS counter electrode with a single-component solid electrolyte show an energy conversion efficiency (<I>η</I>) of 7.1%, which is much greater than that of conventional nanocrystalline TiO<SUB>2</SUB>-based cells and one of the highest values for N719 dye-based ssDSSCs. The enhancement of <I>η</I> is due to the enhancement of current density (<I>J</I> <SUB> <I>sc</I> </SUB>), attributed to the improved light harvesting properties without considerable decrease in fill factor (<I>FF</I>) or open-circuit voltage (<I>V</I> <SUB> <I>oc</I> </SUB>), as confirmed by incident photon-to-electron conversion efficiency (IPCE) and electrochemical impedance spectroscopy (EIS).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Structural color-tunable mesoporus Bragg stacks counter electrodes were prepared. </LI> <LI> BS layers were prepared <I>via</I> the alternating deposition of OM-TiO<SUB>2</SUB> and OM-SiO<SUB>2</SUB> layers. </LI> <LI> The OM layers with controlled <I>RI</I> are templated with amphiphilic graft copolymers. </LI> <LI> DSSC with mesoporous BS layer exhibited enhanced cell performance. </LI> <LI> High efficiency (7.1 %) is due to the higher light harvesting. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Our report is the first work describing the use of organized mesoporous-TiO<SUB>2</SUB> (OM-TiO<SUB>2</SUB>) and organized mesoporous-SiO<SUB>2</SUB> (OM-SiO<SUB>2</SUB>) layers as structural color-tunable mesoporus Bragg stack functionalized counter electrodes in dye-sensitized solar cells (DSSCs). Specifically, there is no previous report regarding the OM-SiO<SUB>2</SUB> layer with small wall thickness and large pore size (>50 nm).</P> <P>[DISPLAY OMISSION]</P>

Water gas shift reaction on the Mn-modified ordered mesoporous Co₃O₄

Ahn, C.I.,Jeong, D.W.,Cho, J.M.,Na, H.S.,Jang, W.J.,Roh, H.S.,Choi, J.H.,Um, S.H.,Bae, J.W. Elsevier 2016 Microporous and mesoporous materials Vol.221 No.-

<P>The novel Mn-modified ordered mesoporous Co3O4 catalysts were investigated for water gas shift reaction (WGSR), which was synthesized through a nano-casting method using a hard template of KIT-6. An incipient wetness impregnation of Mn precursor with different concentrations was applied for preparing Mn-modified mesoporous Co3O4. On 15 wt%Mn impregnated mesoporous Co3O4 (denoted as Mn(15)/meso-Co3O4), WGSR activity was found to be higher among the tested catalysts due to a higher structural stability of the Co3O4 mesopores with a larger surface area. The Mn(15)/meso-Co3O4 also showed stable ordered mesopore structures with an exposed larger number of active metallic cobalt sites on the surfaces even after WGSR. The structural stability was mainly attributed to the strong and stable interactions between cobalt oxides and manganese oxides. With an optimum amount of Mn promoter, Mn plays an important role as a structural stabilizer of the mesoporous Co3O4 as well as an electron modifier by enhancing redox cycle properties of cobalt species and fast mass transport in mesopores. (C) 2015 Elsevier Inc. All rights reserved.</P>

Roles of Al₂O₃ promoter for an enhanced structural stability of ordered-mesoporous Co₃O₄ catalyst during CO hydrogenation to hydrocarbons

Koo, Hyun Mo,Ahn, Chang-Il,Lee, Dong Hyun,Roh, Hyun-Seog,Shin, Chae-Ho,Kye, Hyoungsan,Bae, Jong Wook Elsevier 2018 Fuel Vol.225 No.-

<P><B>Abstract</B></P> <P>A crucial contribution of Al<SUB>2</SUB>O<SUB>3</SUB> pillar for an enhanced structural stability of a highly ordered mesoporous Co<SUB>3</SUB>O<SUB>4</SUB> (Al/m-Co) for CO hydrogenation activity was verified in terms of newly formed stable phases with their interactions. At an optimal 5 wt%Al<SUB>2</SUB>O<SUB>3</SUB> on the Al/m-Co, the activity and stability of Fischer-Trospch synthesis (FTS) reaction were largely enhanced by preserving the highly ordered original mesoporous Co<SUB>3</SUB>O<SUB>4</SUB> structures due to the newly formed strong Al<SUB>2</SUB>O<SUB>3</SUB>-Co<SUB>3</SUB>O<SUB>4</SUB> interactions with the partial formation of the catalytically inactive spinel-type CoAl<SUB>2</SUB>O<SUB>4</SUB> phases in the matrices of the mesoporous Al/m-Co. The main roles of the Al<SUB>2</SUB>O<SUB>3</SUB> pillar on the Al/m-Co were a structural promoter to maintain the highly ordered mesoporous Co<SUB>3</SUB>O<SUB>4</SUB> structures by easily removing the heavy hydrocarbons formed during FTS reaction without significant coke depositions through those large mesopores. The homogeneously distributed Al<SUB>2</SUB>O<SUB>3</SUB> pillaring material less than monolayer on the Al/m-Co surfaces played a crucial role to preserve the original ordered mesoporous Co<SUB>3</SUB>O<SUB>4</SUB> structures through the partial formation of outer surface CoAl<SUB>2</SUB>O<SUB>4</SUB> phases with less blockages of active metallic cobalt sites by heavy coke precursors formed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al<SUB>2</SUB>O<SUB>3</SUB> pillared ordered-mesoporous Co<SUB>3</SUB>O<SUB>4</SUB> (Al/m-Co) showed a superior FTS activity and stability. </LI> <LI> Enhanced structural stability of Al/m-Co was from the partially formed thermally stable CoAl<SUB>2</SUB>O<SUB>4</SUB>. </LI> <LI> Main role of Al<SUB>2</SUB>O<SUB>3</SUB> pillar was the structural promoter to maintain the ordered Co<SUB>3</SUB>O<SUB>4</SUB> structures. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhancement of C?O bond cleavage to afford aromatics in the hydrodeoxygenation of anisole over ruthenium-supporting mesoporous metal oxides

Phan, T.N.,Park, Y.K.,Lee, I.G.,Ko, C.H. Elsevier 2017 Applied Catalysis A Vol.544 No.-

Mesoporous TiO<SUB>2</SUB>, Al<SUB>2</SUB>O<SUB>3</SUB>, silica (SBA-15), and nonporous conventional TiO<SUB>2</SUB> (P25) were used as supports for Ru catalysts in the hydrodeoxygenation (HDO) of anisole. The catalytic reaction was performed in a batch reactor at 200<SUP>o</SUP>C and 5-30bar H<SUB>2</SUB> pressure. It was shown that the selectivity of this catalytic system towards benzene strongly depended on the H<SUB>2</SUB> pressure, being higher at low pressure. Moreover, significant differences in the product distribution were observed for these catalysts suggesting the strong influence of the nature of supports on controlling the reaction pathway. The SBA-15-supported Ru catalyst (Ru/SBA-15) catalyzed the reaction primarily by the hydrogenation (HYD) pathway. The mesoporous-Al<SUB>2</SUB>O<SUB>3</SUB>-supported Ru (Ru/meso-Al<SUB>2</SUB>O<SUB>3</SUB>) promoted the reaction via the HYD and demethylation pathways simultaneously. Mesoporous-TiO<SUB>2</SUB>-supported Ru (Ru/meso-TiO<SUB>2</SUB>) and P25-supported Ru (Ru/P25) promoted higher yield of benzene, indicating its high selectivity for the direct deoxygenation (DDO) route. The use of meso-TiO<SUB>2</SUB> facilitated the spillover effect, leading to the formation of numerous Ti<SUP>3+</SUP> defect sites and oxygen vacancies. As a result, Ru/meso-TiO<SUB>2</SUB> with anatase phase exhibited higher selectivity for the DDO pathway compared to nonporous P25 with a mixed rutile and anatase phase. The results indicated that the phase and mesoporous structure of TiO<SUB>2</SUB> plays an important role in promoting its interaction with Ru particles and in selecting the HDO reaction pathway.

전기 이중층 커패시터를 위한 다공성 탄소나노섬유의 메조 기공 제어 효과

조현기,신동요,안효진,Jo, Hyun-Gi,Shin, Dong-Yo,Ahn, Hyo-Jin 한국재료학회 2019 한국재료학회지 Vol.29 No.3

To improve the performance of carbon nanofibers as electrode material in electrical double-layer capacitors (EDLCs), we prepare three types of samples with different pore control by electrospinning. The speciments display different surface structures, melting behavior, and electrochemical performance according to the process. Carbon nanofibers with two complex treatment processes show improved performance over the other samples. The mesoporous carbon nanofibers (sample C), which have the optimal conditions, have a high sepecific surface area of $696m^2g^{-1}$, a high average pore diameter of 6.28 nm, and a high mesopore volume ratio of 87.1%. In addition, the electrochemical properties have a high specific capacitance of $110.1F\;g^{-1}$ at a current density of $0.1A\;g^{-1}$ and an excellent cycling stability of 84.8% after 3,000 cycles at a current density of $0.1A\;g^{-1}$. Thus, we explain the improved electrochemical performance by the higher reaction area due to an increased surface area and a faster diffusion path due to the increased volume fraction of the mesopores. Consequently, the mesoporous carbon nanofibers are demonstrated to be a very promising material for use as electrode materials of high-performance EDLCs.

Contributions of post-synthesized mesopore structures of ferrierite zeolite for gas-phase dimethyl ether carbonylation activity

Thi Xuan Nguyen,문지원,정현승,한귀영,배종욱 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.6

Mesoporous ferrierite zeolite (FER) synthesized by a post-desilication method was applied for a gas-phase dimethyl ether (DME) carbonylation to confirm the contributions of the newly formed mesoporous structures above 10 nm in size. The distribution of surface acidic sites and extent of coke deposition was significantly altered, resulting in showing different catalytic activity and stability, which were mainly caused by the post-synthesized larger mesopores on the FER. The newly formed mesoporous structures in the range of 5-40 nm on the pristine seed-derived FER (SFER) with a Si/Al molar ratio of 10.4 were largely changed by a desilication/recrystallization duration, and the mesopores significantly increased the surface acidic sites with similar extent of crystallinity even with a lower Si/Al ratio of 6.7-8.6. The increased strong acidic sites corresponding to Brønsted acid sites after an optimal desilication duration for ~3 h on the mesoporous SFER (m-SFER(3)) were mainly responsible for an increased DME carbonylation activity with smaller formation of coke precursors due to facile mass transport phenomena through its lager mesopores.

Effect of mesopore-induced strain/stress on the thermoelectric properties of mesoporous ZnO thin films

Hong, Min-Hee,Shim, Dong Il,Cho, Hyung Hee,Park, Hyung-Ho Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.446 No.-

<P><B>Abstract</B></P> <P>In present study, induced strain and stress effect of mesoporous structure on the thermoelectric properties of ZnO thin films were systematically investigated. In this work, mesoporous ZnO thin films were synthesized by evaporation-induced self-assembly and sol-gel process. As the pore structure is formed, the grain growth of ZnO is inhibited and lattice distortion is induced. In this paper, strain/stress induction according to surfactant (Brij-S10) concentration was analyzed through Williamson-Hall analysis. And the relationship between strain induction and thermoelectric properties was studied. 0.07 M ratio of Brij-S10 to Zn induces the enhanced thermoelectric properties as compared with pristine ZnO thin films. Hence, the induced strain and stress could play an important role in enhancing the thermoelectric properties of mesoporous ZnO thin films.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of mesoporous ZnO thin films using evaporation-induced self-assembly process. </LI> <LI> XRD peak was broadened as increased surfactant concentration. </LI> <LI> Induced strain, stress, and energy density was calculated by using Williamson-Hall analysis. </LI> <LI> Improved thermoelectric property followed by mesoporous structure and tensile strain. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Real-time regeneration for Al₂O₃-pillared mesoporous-Co₃O₄ in Fischer-Tropsch synthesis

구현모,곽태열,배종욱 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Ordered-mesoporous materials have a relatively high surface area and a uniform meso-pore structure and can be used for gas sensors or heterogeneous catalysis. However, the pristine mesoporous materials in Fischer-Tropsch synthesis showed a severe structural instability. In this study, the mesoporous-Co₃O₄ was synthesized using hard template of KIT-6, and structural stability was improved by using Al₂O₃, an irreducible metal oxide as a pillar. In addition, its long-term stability can be ensured by injecting n-octane in real time. When a proper amount of alumina (5~10%) was impregnated, the catalyst stability was better than that of pristine mesoporous-Co₃O₄. However, the deposition of hydrocarbon (wax) on those catalysts was significant due to a higher activity. The deposited waxy hydrocarbons was effectively removed by the saturated hydrocarbons (n-octane) injected during FTS reaction, and the catalytic activity was regenerated with time on stream.

Synthesis of mesoporous Ferrierite by desilication and its application to gas-phase carbonylation of DME

( Nguyenxuan ),배종욱 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

The mesoporous Ferrierite (FER) zeolite was synthesized by using cetyltrimethylammonium bromide (CTAB) as organic structure-directing agent (OSDA) through desilication method to verify the effects of diffusions and coke depositions in the post-synthesized larger pores. The effects of the stirring duration and temperature of desilication step were investigated by using two different Na- and H-form FER to understand the formation mechanisms of the mesopores. The post-synthesized mesoporous FER from Na-form FER (FER-Na) revealed a higher activity than that of H-form FER (FER-H) during a gas-phase dimethyl ether (DME) carbonylation. The higher catalytic activity on the FER-Na was mainly attributed to the increased acidic site density as well as larger amount of Brønsted acid sites through an easy desiccation on the pristine FER-Na zeolite.

축전식 탈염 공정을 위한 메조포러스 탄소 전극

이동주,박진수,Lee, Dong-Ju,Park, Jin-Soo 한국전기화학회 2014 한국전기화학회지 Vol.17 No.1

다공성의 활성탄소와 상대적으로 입자크기가 더 작은 carbon black을 여러 비율로 혼합하여 다양한 적층배열 구조를 갖는 축전식 탈염용 전극을 제조하였고 활성탄소만 존재하는 전극과 비교 분석하였다. 연구 결과 carbon black의 양이 증가할수록 탄소체의 배열 구조가 조밀해지는 것을 관찰하였고, mesopore가 약 10% 증가하는 것으로 나타났다. 순환전압전류법을 이용하여 축전용량을 살펴보았을 때 carbon black만으로는 이온흡착에 대한 영향이 거의 없지만 활성탄소체와 혼합하여 carbon black의 양이 증가할수록 비축전용량 역시 증가하는 것을 관찰하였다. 최종적으로 셀에 전극을 채용하여 탈염실험을 수행한 결과, carbon black의 양이 가장 많이 함유된 전극의 탈염 성능이 가장 우수하였고, pH의 변화의 폭이 가장 좁았다. 또한, 축전된 전하의 분석을 통해 비페러데이 전류의 비율이 증가하는 것으로 나타나 페러데이 반응에 대한 영향이 감소하는 것을 관찰하였다. 이는 carbon black의 첨가로 전극의 적층배열 구조가 변형함으로써 mesopore의 비율이 증가해 페러데이 반응에 의한 영향이 감소하였고, 탈염 성능 역시 증가하는 것을 알 수 있었다. Carbon electrodes for capacitive deionization were fabricated through mixing two different carbon powders (activated carbon powder, carbon black) with different particle sizes to investigate physical or electrochemical properties and finally desalination performances of the electrodes with various compositions of two carbon powders in weight and were compared with the electrode consisting of activated carbon. As a result, the electrode structure became more packed as increasing the amount of carbon black and resulted in 10% increase in mesopore fraction. The specific capacitance obtained from cyclic voltammograms of various electrodes showed that the electrode containing carbon black only had 107.4 F/g, while the specific capacitance of the electrode having more amount of carbon black increased and was higher than the one having no carbon black. The results of desalination runs in a capacitive deionization cell exhibited that the electrode having the highest amount of carbon black (1 wt%) in this study had the highest desalting efficiency, and no significant pH variation was observed during the runs. It was analyzed using accumulated charge that the fraction of non-Faraday current increased as the amount of carbon black increased in the electrodes. It can be concluded that the addition of carbon black changed the electrode structure resulting in an increase in the fraction of mesopore and finally enhanced the desalting efficiency by decreasing Faraday current.