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Hemal Weerasinghe,Hui-Fen Wu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.124 No.-
Vanadium dioxide has excellent absorbance in near-infrared (NIR) wavelengths making it a perfect candidatefor photothermal applications based on solar energy. However, up to date, it was mainly applied ina lithium-ion battery. This study is for the second time, to utilize VO2-based nanomaterials as a photothermalmaterial for solar steam generation to purify seawater and wastewater. The study has proposeda straightforward and promising room temperature approach to synthesize a mixture of twovanadium oxide nanosheets with a major fraction of VO2 (B) nanosheets with the major part for VO2. nH2O and a minor fraction of V2O5.nH2O which have demonstrated excellent photothermal capabilityfor water purification. The highest steady state temperature of 87 C was reported by the synthesizednanosheets that were spray coated on cellulose fabric for the solar absorption purpose under one sun illuminationfor water purification. The as-prepared photo absorber was capable of reaching the higheststeady temperature at high speed (within 10 minutes). The synthesized 2D VO2/V2O5.nH2O nanosheetsand cellulose fabric combination of solar steam generator gained a competitive evaporation rate of1.31 kgm-2h1 and a percentage efficiency of 89.7% under one sun illumination. The current approachwas successfully applied to three real-world samples to obtain clean or drinking water. All three samplesshowed excellent improvements in their water quality compared with their initial states in a single distillation. Two samples can even reach the quality of World Health Organization (WHO)-recommendedstandards for drinking water. The current approach has opened a new platform for the utilization ofVO2-based nanosheets for obtaining clean water from seawater and wastewater by solar energyutilization.
국제 공동 연구를 통한 태양에너지 활용 열화학 물분해 그린 수소 생산 연구 및 E-fuel 생산 연구 동향 보고
조현석(Hyun-Seok Cho) 한국신재생에너지학회 2024 신재생에너지 Vol.20 No.1
Global sustainable energy needs and carbon neutrality goals make hydrogen a key future energy source. South Korea and Japan lead with proactive hydrogen policies, including South Korea’s Hydrogen Law and Japan’s strategy updates aiming for a hydrogen-centric society by 2050. A notable advance is the solar thermal chemical water-splitting cycle for green hydrogen production, spotlighted by Korea Institute of Energy Research (KIER) and Niigata University’s joint initiative. This method uses solar energy to split water into hydrogen and oxygen, offering a carbon-neutral hydrogen production route. The study focuses on international collaboration in solar energy for thermochemical water-splitting and E-fuel production, highlighting breakthroughs in catalyst and reactor design to enhance solar thermal technology’s commercial viability for sustainable fuel production. Collaborations, like ARENA in Australia, target global carbon emission reduction and energy system sustainability, contributing to a cleaner, sustainable energy future.
인공 태양열 집광장치를 이용한 Fe-CeO₂ 전이금속 화합물이 코팅된 세라믹 금속 산화물 반응체의 열화학 이단계 물분해 싸이클 및 수소 생산의 실험적 연구
조현석(Hyun-Seok Cho),사카이 유(Yu Sakai),고다마 타츠야(Tatsuya Kodama) 한국태양에너지학회 2021 한국태양에너지학회 논문집 Vol.41 No.4
A newly developed Fe-CeO₂-coated ceramic-foam device has been designed, fabricated, and tested for higher oxygen/hydrogen productivity in the thermochemical two-step water-splitting cycle. For the fabrication of the Fe-CeO₂-coated ceramic-foam device, the direct depositing method was adopted. This method, in which elemental Fe is doped into CeO₂ and this is coated onto the ceramic foam matrix surface, has advantages for the fabrication of reactive foam devices. In the synthesis of Fe-CeO₂, the degree of Fe doping was set at 10, 15, or 30 ㏖%, and the amount of Fe-CeO₂ loaded onto the foam matrix surface was fixed at 30 wt%. A 3㎾th sun-simulator was used as the heat source in the thermochemical two-step water-splitting cycle for hydrogen production. The thermal reduction step for releasing oxygen was conducted at an operating temperature of 1400℃ for 45 minutes, and the subsequent water-decomposition step for producing hydrogen was carried out at 1200℃ for 60 minutes. The performance of the newly developed Fe-CeO₂ foam device was compared with that of previously tested foam devices fabricated by the co-precipitation method and the spin-coating method.
Monisha Rastogi,H.S. Kushwaha,Rahul Vaish 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.2
This study investigates BaTiO3 decorated reduced graphene oxide sheetsas a potential visible light active catalyst for dye degradation (RhodamineB). The composites were prepared through conventional hydrothermalsynthesis technique using hydrazine as a reducing agent. A number oftechniques have been employed to affirm the morphology, compositionand photocatalytic properties of the composites; these include UV-visiblespectrophotoscopy that assisted in quantifying the concentration differenceof Rhodamine B. The phase homogeneity of the composites was examinedthrough x-ray powder diffraction (XRD) and high resolution transmissionelectron microscopy (HRTEM) was employed to confirm the orientationof the BaTiO3 particles over the reduced graphene oxide sheets. Photoluminescence (PL) emission spectra assisted in determining thesurface structure and excited state of the catalyst. Fourier transformedinfrared(FTIR) spectra investigated the vibrations and adsorption peak of the composites, thereby ascertaining the formation ofreduced graphene oxide. In addition, diffuse reflectance spectroscopy (DRS) demonstrated an enhanced absorption in the visibleregion. The experimental investigations revealed that graphene oxide acted as charge collector and simultaneously facilitatedsurface adsorption and photo-sensitization. It could be deduced that BaTiO3-reduced graphene oxide composites are ofsignificant interest the field of water purification through solar photocatalysis.
Bae, Sanghyun,Kim, Hyunwoo,Jeon, Dasom,Ryu, Jungki American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.8
<P>We studied the kinetics of photoelectrochemical (PEC) water oxidation using a model photoanode BiVO<SUB>4</SUB> modified with various water oxidation catalysts (WOCs) by electrochemical impedance spectroscopy. In particular, we prepared BiVO<SUB>4</SUB> photoanodes with catalytic multilayers (CMs), where cationic polyelectrolytes and anionic polyoxometalate (POM) WOCs were assembled in a desired amount at a nanoscale precision, and compared their performance with those with well-known WOCs such as cobalt phosphate (CoPi) and NiOOH. Our comparative kinetics analysis suggested that the deposition of the CMs improved the kinetics of both the photogenerated charge carrier separation/transport in bulk BiVO<SUB>4</SUB> due to passivation of surface recombination centers and water oxidation at the electrode/electrolyte interface due to deposition of efficient molecular WOCs. On the contrary, the conventional WOCs were mostly effective in the former and less effective in the latter, which is consistent with previous reports. These findings explain why the CMs exhibit an outstanding performance. We also found that separated charge carriers can be efficiently transported to POM WOCs via a hopping mechanism due to the delicate architecture of the CMs, which is reminiscent of natural photosynthetic systems. We believe that this study can not only broaden our understanding on the underlying mechanism of PEC water oxidation but also provide insights for the design and fabrication of novel electrochemical and PEC devices, including efficient water oxidation photoanodes.</P> [FIG OMISSION]</BR>
Kargar, Alireza,Sun, Ke,Jing, Yi,Choi, Chulmin,Jeong, Huisu,Zhou, Yuchun,Madsen, Kristian,Naughton, Perry,Jin, Sungho,Jung, Gun Young,Wang, Deli American Chemical Society 2013 Nano letters Vol.13 No.7
<P>We report the fabrication of three-dimensional (3D) branched nanowire (NW) heterostructures, consisting of periodically ordered vertical Si NW trunks and ZnO NW branches, and their application for solar water splitting. The branched NW photoelectrodes show orders of magnitudes higher photocurrent compared to the bare Si NW electrodes. More interestingly, selective photoelectrochemical cathodic or anodic behavior resulting in either solar water oxidation or reduction was achieved by tuning the doping concentration of the p-type Si NW core. Specifically, n-ZnO/p-Si branched NW array electrodes with lightly doped core show broadband absorption from UV to near IR region and photocathodic water reduction, while n-ZnO/p<SUP>+</SUP>-Si branched NW arrays show photoanodic water oxidation with photoresponse only to UV light. The photoelectrochemical stability for over 24 h under constant light illumination and fixed biasing potential was achieved by coating the branched NW array with thin layers of TiO<SUB>2</SUB> and Pt. These studies not only reveal the promise of 3D branched NW photoelectrodes for high efficiency solar energy harvesting and conversion to clean chemical fuels, but also developing understanding enabling rational design of high efficiency robust photocathodes and photoanodes from low-cost and earth-abundant materials allowing practical applications in clean renewable energy.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-7/nl304539x/production/images/medium/nl-2012-04539x_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl304539x'>ACS Electronic Supporting Info</A></P>
Hot water oxidation 공정을 이용한 고품위 실리콘 기판 제작
박효민(Park, Hyo-Min),탁성주(Tark, Sung-Ju),강민구(Kang, Min-Gu),박성은(Park, Sung-Eun),김동환(Kim, Dong-Whan) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06
높은 소수반송자 수명(life-time)을 가지는 고품위 실리콘 기판은 고효율 실리콘 이종접합 태양전지 제작을 위한 중요 요소 기술 중 하나이다. 본 연구에서는 n-type c-Si 기판을 이용한 고효율 실리콘 이종접합 태양전지제작을 위해 hot water oxidation(HWO) 공정을 이용하여 고품위 실리콘 기판을 제작하였다. 실리콘 기판의 특성 분석은 Qusi-steady state photoconductance (QSSPC)를 이용하여 소수반송자 수명을 측정하였으며, 기판의 면저항 및 wetting angle을 측정하여 공정에 따른 특성변화를 분석하였다. Saw damage etching 된 기판을 웨이퍼 표면으로부터 particle, 금속 불순물, 유기물 등의 오염을 제거하기 위해 60{sim}85?C로 가열된 Ammonia수, 과산화수소수(NH₄OH/H₂O₂/H₂O), 염산 과산화수소수(HCL/H₂O₂/H₂O) 및 실온 희석불산(DHF) 중에 기판을 각각 10분 정도씩 침적하여, 각각의 약액 처리 후에 매회 10분 정도씩 순수(DI water)에서 rinse하여 RCA 세정을 진행한 후 HWO 공정을 통해 기판 표면에 얇은 산화막 을 형성시켜 패시베이션 해주었다. HF를 이용하여 자연산화막을 제거시 HWO 공정을 거친 기판은 매끄러운 표면과 패시베이션 영향으로 기판의 소수 반송자 수명이 증가하며, 태양전지 제작시 접촉저항을 감소시켜 효율을 증가 시킬수 있다. HWO 공정은 반응조 안의 DI water 온도와 반응 시간에 따라 life-time을 측정하여 진행하였으며, 이후 PE-CVD법으로 증착된 a-Si:H layer 및 투명전도 산화막, 금속전극을 증착하여 실리콘 이종접합 태양전지를 제작하였다.