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Kang, Jin Soo,Kang, Jiho,Chung, Dong Young,Son, Yoon Jun,Kim, Seoni,Kim, Sungjun,Kim, Jin,Jeong, Juwon,Lee, Myeong Jae,Shin, Heejong,Park, Subin,Yoo, Sung Jong,Ko, Min Jae,Yoon, Jeyong,Sung, Yung-Eun The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.41
<P>Metal-organic framework (MOF)-derived carbon materials have been widely used as catalysts for a variety of electrochemical energy applications, and thermally carbonized zinc-2-methylimidazole (ZIF-8) has shown particularly high performance owing to its microporous structure with a large surface area. However, in the presence of bulky chemical species, such as triiodide, in mesoscopic dye-sensitized solar cells (DSCs), the small pore size of carbonized ZIF-8 causes a significant limitation in mass transfer and consequentially results in a poor performance. To resolve this problem, we herein report a simple strategy to enlarge the pore sizes of ZIF-8-derived carbon by increasing the dwelling time of Zn in ZIF-8 during the thermal carbonization process. A thin and uniform polydopamine shell introduced on the surface of ZIF-8, with the aim of retarding the escape of vaporized Zn species, leads to a dramatic increase in pore sizes, from the micropore to mesopore range. The porosity-tailored carbonized ZIF-8 manifests an excellent electrocatalytic performance in triiodide reduction, and when it was applied as the counter electrode of DSCs, an energy conversion efficiency of up to 9.03% is achievable, which is not only superior to that of the Pt-based counterpart but also among the highest performances of DSCs employing carbonaceous electrocatalysts.</P>
Highly Efficient Bifacial Dye-Sensitized Solar Cells Employing Polymeric Counter Electrodes
Kang, Jin Soo,Kim, Jin,Kim, Jae-Yup,Lee, Myeong Jae,Kang, Jiho,Son, Yoon Jun,Jeong, Juwon,Park, Sun Ha,Ko, Min Jae,Sung, Yung-Eun American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.10
<P>Dye-sensitized solar cells (DSCs) are promising solar energy conversion devices with aesthetically favorable properties such as being colorful and having transparent features. They are also well-known for high and reliable performance even under ambient lighting, and these advantages distinguish DSCs for applications in window-type building-integrated photovoltaics (BIPVs) that utilize photons from both lamplight and sunlight. Therefore, investigations on bifacial DSCs have been done intensively, but further enhancement in performance under back-illumination is essential for practical window-BIPV applications. In this research, highly efficient bifacial DSCs were prepared by a combination of electropolymerized poly(3,4-ethylenedioxythiphene) (PEDOT) counter electrodes (CEs) and cobalt bipyridine redox ([Co(bpy)<SUB>3</SUB>]<SUP>3+/2+</SUP>) electrolyte, both of which manifested superior transparency when compared with conventional Pt and iodide counterparts, respectively. Keen electrochemical analyses of PEDOT films verified that superior electrical properties were achievable when the thickness of the film was reduced, while their high electrocatalytic activities were unchanged. The combination of the PEDOT thin film and [Co(bpy)<SUB>3</SUB>]<SUP>3+/2+</SUP> electrolyte led to an unprecedented power conversion efficiency among bifacial DSCs under back-illumination, which was also over 85% of that obtained under front-illumination. Furthermore, the advantage of the electropolymerization process, which does not require an elevation of temperature, was demonstrated by flexible bifacial DSC applications.</P> [FIG OMISSION]</BR>
Kang, Jin Soo,Kang, Jiho,Chae, Jiyoung,Son, Yoon Jun,Jeong, Juwon,Kim, Jin,Kim, Jae-Yup,Kang, Soon Hyung,Ahn, Kwang-Soon,Sung, Yung-Eun The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.14
<P>Recent advances in optoelectronic properties of quantum dots (QDs) have led to significant improvement in QD-sensitized solar cells (QDSCs); however, for practical utilization of these devices, performance of the constituent electrocatalytic counter electrodes (CEs) needs to be further enhanced. Pt CEs are prone to severe sulfur poisoning by polysulfide redox electrolytes in QDSCs, and Cu<SUB>2</SUB>S CEs with state-of-the-art activity are vulnerable to light-induced degradations. In this study, for the first time, tungsten carbide (W<SUB>2</SUB>C) films were used as CEs for QDSCs. Instead of the conventional methods of carbide nanomaterial synthesis that involve thermal treatments in toxic/explosive atmospheres, room-temperature vapor deposition was employed for the preparation of W<SUB>2</SUB>C electrodes, and dendritic nanostructures with large surface areas were obtained. Although the electronic structures of Pt and W<SUB>2</SUB>C are highly similar, W<SUB>2</SUB>C was completely inert to sulfur poisoning. This led to a substantial improvement in the electrocatalytic performance for polysulfide reduction, and ∼27% enhancement in power conversion efficiency was achieved when Pt CEs were replaced with W<SUB>2</SUB>C CEs in QDSCs. Moreover, QDSCs comprising W<SUB>2</SUB>C CEs manifested excellent photostability, and they showed performances superior to those of QDSCs comprising state-of-the-art Cu<SUB>2</SUB>S electrodes within 40 min of operation, without any sign of drop in efficiency.</P>
과초산 전처리 목질 바이오매스의 화학 조성에 따른 효소 당화 특성
강주원(Juwon Kang),유원재(Won-Jae Youe),강규영(Kyu-Young Kang) 한국펄프·종이공학회 2017 펄프.종이기술 Vol.49 No.4
In this study, the lignocellulosic fibers from Quercus mongolica and Larix kaempferi wood chips pretreated with peracetic acid were enzymatically hydrolyzed by CTec2 and HTec2, and the characteristics of enzymatic saccharification were compared and analyzed with the difference of chemical composition of biomass. The pretreated wood fibers of two species could be hydrolyzed only with CTec2. The optimum CTec2 dosage for wood fibers was different depending on the species of the biomass (Quercus mongolica : ~19 FPU/g biomass, Larix kaempferi : ~21 FPU/g biomass), however, it could be economized by using together with endoxylanase, HTec2. The synergy effect of hydrolysis reaction was showed in the saccharification by using both of enzymes, and the most effective mixing condition of enzymes was dependent on biomass (CTec2:HTec2; 7:3 in Quercus mongolica , 9:1 in Larix kaempferi ). The hydrolysis of xylan has been activated by endoxylanase, therefore, it could saved the CTec2 dosage and economized enzymatic saccharification of wood fibers, especially in the case of Quercus mongolica.