• Computers and Concrete
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• 제6권2호
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• pp.155-165
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• 2009

Splitting tensile strength (STS) of high-performance concrete (HPC) is one of the important mechanical properties for structural design. This property is related to compressive strength (CS), water/binder (W/B) ratio and concrete age. This paper presents a clustering-based fuzzy model for the prediction of STS based on the CS and (W/B) at a fixed age (28 days). The data driven fuzzy model consists of three main steps: fuzzy clustering, inference system, and prediction. The system can be analyzed directly by the model from measured data. The performance evaluations showed that the fuzzy model is more accurate than the other prediction models concerned.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.87-87
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• 2010

Photoelectrochemical (PEC) systems are promising methods of producing H2 gas using solar energy in an aqueous solution. The photoelectrochemical properties of numerous metal oxides have been studied. Among them, the PEC systems based on TiO2 have been extensively studied. However, the drawback of a PEC system with TiO2 is that only ultraviolet (UV) light can be absorbed because of its large band gap (3.2 - 3.4 eV). Two approaches have been introduced in order to use PEC cells in the visible light region. The first method includes doping impurities, such as nitrogen, into TiO2, and this technique has been extensively studied in an attempt to narrow the band gap. In comparison, research on the second method, which includes visible light water splitting in molecular photosystems, has been slow. Mallouk et al. recently developed electrochemical water-splitting cells using the Ru(II) complex as the visible light photosensitizer. the dye-sensitized PEC cell consisted of a dye-sensitized TiO2 layer, a Pt counter electrode, and an aqueous solution between them. Under a visible light (< 3 eV) illumination, only the dye molecule absorbed the light and became excited because TiO2 had the wide band gap. The light absorption of the dye was followed by the transfer of an electron from the excited state (S*) of the dye to the conduction band (CB) of TiO2 and its subsequent transfer to the transparent conducting oxide (TCO). The electrons moved through the wire to the Pt, where the water reduction (or H2 evolution) occurred. The oxidized dye molecules caused the water oxidation because their HOMO level was below the H2O/O2 level. Organic dyes have been developed as metal-free alternatives to the Ru(II) complexes because of their tunable optical and electronic properties and low-cost manufacturing. Recently, organic dye molecules containing multi-branched, multi-anchoring groups have received a great deal of interest. In this work, tri-branched tri-anchoring organic dyes (Dye 2) were designed and applied to visible light water-splitting cells based on dye-sensitized TiO2 electrodes. Dye 2 had a molecular structure containing one donor (D) and three acceptor (A) groups, and each ended with an anchoring functionality. In comparison, mono-anchoring dyes (Dye 1) were also synthesized. The PEC response of the Dye 2-sensitized TiO2 film was much better than the Dye 1-sensitized or unsensitized TiO2 films.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1931-1932
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• 2014

• 청정기술
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• 제3권2호
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• pp.74-86
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• 1997

최근 청정기술의 필요성이 증가하면서 막분리 공정에 의한 산업폐수 처리기술에 대한 관심이 높아가고 있다. 이 연구는 중화법과 water-splitting electrodialysis (WSED)를 이용하여 금속을 포함하고 있는 폐수에서 유용한 물질을 회수하고 무방류계를 실현하기 위한 것이다. 본 연구에서는 산폐수와 혼합폐수 처리의 공정 설계를 위한 공정의 흐름를 확립하였고, 이 공정에 따른 물질수지를 계산하였다. 또한 주요 단위공정인 침전조와 산회수공정의 운전인자에 대한 실험을 수행하였다. 침전공정에서는 KOH와 NaOH를 중화제로 이용하여 pH에 따른 침전효율과 슬러지양을 비교하였으며 산회수 공정에서는 KCl과 NaCl을 합성원료로 이용하여 WSED의 막구조에 따른 회수효율을 조사하였다.

• Advances in Energy Research
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• 제2권1호
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• pp.33-45
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• 2014

Photocatalytic hydrogen generation by water splitting ($H_2O_{(1)}{\rightarrow}H_2_{(g)}+1/2O_2_{(g)}$) has been studied on photocatalysts based on Zn, Cd, Fe and Cu, synthesized by coprecipitation. Iron and copper nanoparticles were incorporated as cocatalysts to enhance the photocatalytic activity of the ZnCd solid solution. The effect of the different synthesis parameters (temperature, elemental atomic ratios, amount of Cu and Fe incorporated in the catalyst and calcination temperature) on the photocatalytic production of hydrogen has been studied in order to determine the best experimental synthesis conditions. The catalysts have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and BET. The experiments of photocatalytic water splitting were performed in aqueous solution of the photocatalysts previously dispersed in a soft ultrasound bath. The photocatalysts were irradiated under different lights ranging from 220 to 700 nm. The photocatalytic activity was found to be clearly dependent on the specific area of the photocatalyst.

• 한국수소및신에너지학회논문집
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• 제19권4호
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• pp.305-312
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• 2008

ZnO/Zn redox cycle is the one of the promising thermochemical cycles for hydrogen production via water splitting with high temperature heat source like a concentrated solar energy. This paper reports the particle size effect of Zinc on water splitting behavior. Water splitting reaction experiments were carried out at isothermal conditions of 350 and 400$^{\circ}C$ in TGA (Thermo Gravimetric Analyzer) using four commercial Zinc powders (nano, <10 ${\mu}m$, <150 ${\mu}m$ and $150{\sim}600\;{\mu}m$ particle sizes). Before the experiments, average particle size of Zinc powders was analyzed by PSA (Particle Size Analysis). After the experiments, XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscope) analyses were conducted on the samples. The experimental results showed that particle size had a effect on the conversion of Zinc to ZnO. Zinc conversion was increased, as the particle size decreased. Especially, the nano size particles were aggregated and the particle's morphology changed on the surface during hydrolysis reaction.

• 멤브레인
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• 제14권3호
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• pp.185-191
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• 2004

원자력 발전의 고온 가스로(high temperature gas-cooled reactor, HTGR)의 냉각제로 사용되는 He가스의 열에너지를 이용하여 물을 분해해서 수소를 생산하는 "열화학적 수소제조 IS프로세스"에 대해 설명하였다. 특히, 분리막 기술의 이용에 관한 연구를 중점으로 정리하였다. 고온 원자력 열에너지를 이용한 열화학적 수소 제조법은 실현 가능한 단계까지 왔다고 생각되며, 아직 연구 개발 과제가 많이 남아 있지만, 미래의 청정에너지 중의 하나인 수소를 대량 생산할 수 있는 가능성을 갖고 있다.

• 전기화학회지
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• 제17권1호
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• pp.1-6
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• 2014

본 총설은 질화 갈륨(GaN)을 이용한 광전기화학적 물분해 연구에 대해 정리하였다. GaN는 화학적으로 안정하고 에너지 띠간격 조절이 자유롭다는 장점으로 최근 물분해를 위한 새로운 광전극 물질로 연구되고 있다. 다른 화합물 반도체 물질은 강산 혹은 강염기 전해액에 의해 쉽게 부식되기 때문에 광산화전극(photoanode)으로는 사용이 어려운 반면, n형 GaN는 뛰어난 안정성 덕분에 산화 분위기의 산소 발생 전극으로도 활용이 가능하다. 또한, 최근에는 p형 GaN을 환원전극으로 이용한 광전극에 대한 연구도 보고되었다. GaN 물질이 실제 응용되기 위해 필요한 과제들에 대해 다루었다.

• 한국세라믹학회지
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• 제55권3호
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• pp.185-202
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• 2018

Photoelectrochemical (PEC) cells can convert solar energy, the largest potential source of renewable energy, into hydrogen fuel which can be stored, transported, and used on demand. In terms of cost competitiveness compared with fossil fuels, however, both photocatalytic efficiency and cost-effectiveness must be achieved simultaneously. Improvement of cost-effective, scalable, versatile, and eco-friendly fabrication methods has emerged as an urgent mission for PEC cells, and solution-based fabrication methods could be capable of meeting these demands. Herein, we review recent challenges for various nanostructured oxide photoelectrodes fabricated by solution-based processes. Hematite, tungsten oxide, bismuth vanadate, titanium oxide, and copper oxides are the main oxides focused on, and various strategies have been attempted with respect to these photocatalyst materials. The effects of nanostructuring, heterojunctions, and co-catalyst loading on the surface are discussed. Our review introduces notable solution-based processes for water splitting photoelectrodes and gives an outlook on eco-friendly and cost-effective approaches to solar fuel generation and innovative artificial photosynthesis technologies.

• Rapid Communication in Photoscience
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• 제4권4호
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• pp.82-85
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• 2015

Photoelectrochemical cell (PEC) is one of the attractive ways to produce clean and renewable energy. However, solar to hydrogen production via PEC system generally requires high external bias, because of material's innate electronic band potential relative to hydrogen reduction potential and/or charge separation issue. For spontaneous photo-water splitting, here, we design dye-sensitized solar cell (DSSC) and their monolithic tandem cell incorporated with a $BiVO_4$ photoanode. $BiVO_4$ has high conduction band edge potential and suitable band gap (2.4eV) to absorb visible light. To achieve efficient $BiVO_4$ photoanode system, electron and hole mobility should be improved, and we demonstrate a tandem cell in which $BiVO_4/WO_3$ film is connected to cobalt complex based DSSC.