Dye-sensitized solar cells based on trench structured TiO2 nanotubes in Ti substrate

Kang-Pil Kim,Sang-Ju Lee,Dae-Hwan Kim,Dae-Kue Hwang,허영우 한국물리학회 2013 Current Applied Physics Vol.13 No.4

We have proposed dye-sensitized solar cells (DSSCs) with trench-type TiO2 nanotube structure to improve the low device efficiency of conventional TiO2 nanotube DSSCs using Ti substrate. Compared to the conventional standing-type TiO2 nanotube structure based DSSCs, the trench-type TiO2 nanotube structure based DSSCs have shown an improvement of device efficiency of approximately 40% due to the large increase of Jsc. In the trench-type TiO2 nanotube structure, the contact area between the TiO2nanotube sidewall and the Ti substrate is significantly increased. This increase of contact area provides more charge transport paths than exist in the conventional standing-type TiO2 nanotube structure and reduces the electrical resistance between the Ti substrate and the TiO2 nanotubes. Therefore, the remarkable increase of Jsc is the result of the charge collection efficiency, which is improved due to the increase of contact area between the TiO2 nanotube sidewall and the Ti substrate in the trench-type TiO2nanotube structure. The fabrication of the trench-type TiO2 nanotube structure is an effective manufacturing process for improving the device efficiency of TiO2 nanotube based DSSCs using Ti substrate. DSSCs having an 11.9 mm thick trench-type TiO2 nanotube structure have shown an efficiency of 5.74%.

Dye-sensitized solar cells based on trench structured TiO₂ nanotubes in Ti substrate

Kim, K.P.,Lee, S.J.,Kim, D.H.,Hwang, D.K.,Heo, Y.W. Elsevier 2013 Current Applied Physics Vol.13 No.4

We have proposed dye-sensitized solar cells (DSSCs) with trench-type TiO<SUB>2</SUB> nanotube structure to improve the low device efficiency of conventional TiO<SUB>2</SUB> nanotube DSSCs using Ti substrate. Compared to the conventional standing-type TiO<SUB>2</SUB> nanotube structure based DSSCs, the trench-type TiO<SUB>2</SUB> nanotube structure based DSSCs have shown an improvement of device efficiency of approximately 40% due to the large increase of Jsc. In the trench-type TiO<SUB>2</SUB> nanotube structure, the contact area between the TiO<SUB>2</SUB> nanotube sidewall and the Ti substrate is significantly increased. This increase of contact area provides more charge transport paths than exist in the conventional standing-type TiO<SUB>2</SUB> nanotube structure and reduces the electrical resistance between the Ti substrate and the TiO<SUB>2</SUB> nanotubes. Therefore, the remarkable increase of Jsc is the result of the charge collection efficiency, which is improved due to the increase of contact area between the TiO<SUB>2</SUB> nanotube sidewall and the Ti substrate in the trench-type TiO<SUB>2</SUB> nanotube structure. The fabrication of the trench-type TiO<SUB>2</SUB> nanotube structure is an effective manufacturing process for improving the device efficiency of TiO<SUB>2</SUB> nanotube based DSSCs using Ti substrate. DSSCs having an 11.9 μm thick trench-type TiO<SUB>2</SUB> nanotube structure have shown an efficiency of 5.74%.

Anatase와 Rutile 결정상 비율에 따른 TiO2 nanotube의 OH radical 생성량 비교 연구

이효주,이용호,박대원 한국물환경학회 2019 한국물환경학회지 Vol.35 No.6

This study was carried out to improve the photocatalytic reaction of TiO2 photocatalyst. During the photocatalytic reaction, OH radicals are generated and they have an excellent oxidation capability for wastewater treatment. To evaluate the OH radicals generated according to crystallographic structure of TiO2 nanotubes photocatalyst, a probe compound, 4-Chlorobenzoic acid was monitored to evaluate OH radical. Ultraviolet light was applied for photocatalytic reaction of TiO2. The 4-Chlorobenzoic acid solution was prepared at laboratory. TiO2 nanotube was grown on titanium plate by using anodization method. The annealing temperature for TiO2 nanotube was varied from 400 to 900 ℃ and the crystal forms of the TiO2 nanotube was analyzed. Depending on annealing temperature, TiO2 nanotubes have shown different crystal forms; 100% anatase (0 % rutile), 18.4 % rutile (81.6 % anatase), 36.6 % rutile (63.4 % anatase) and 98.6% rutile (1.4% anatase). As the annealing temperature increases, the rutile ratio increases. OH radical generation from 18.4 % rutile TiO2 nanotube plate was about 3.8 times higher than before annealing and 1.4 times higher than only 100 % anatase-TiO2 nanotube. The efficiency of the 18.4% rutile TiO2 nanotube was the best in comparison to TiO2 nanotube with 18.4 %, 36.6 % and 98.6 % rutile. As a result, photocatalytic ability of 18.4 % rutile-TiO2 nanotube plate was higher than 100 % anatase-TiO2 nanotube plate.

Anatase와 Rutile 결정상 비율에 따른 TiO₂ nanotube의 OH radical 생성량 비교 연구

이효주 ( Hyojoo Lee ),이용호 ( Yongho Lee ),박대원 ( Daewon Pak ) 한국물환경학회(구 한국수질보전학회) 2019 한국물환경학회지 Vol.35 No.6

This study was carried out to improve the photocatalytic reaction of TiO₂ photocatalyst. During the photocatalytic reaction, OH radicals are generated and they have an excellent oxidation capability for wastewater treatment. To evaluate the OH radicals generated according to crystallographic structure of TiO₂ nanotubes photocatalyst, a probe compound, 4-Chlorobenzoic acid was monitored to evaluate OH radical. Ultraviolet light was applied for photocatalytic reaction of TiO₂. The 4-Chlorobenzoic acid solution was prepared at laboratory. TiO₂ nanotube was grown on titanium plate by using anodization method. The annealing temperature for TiO₂ nanotube was varied from 400 to 900 ℃ and the crystal forms of the TiO₂ nanotube was analyzed. Depending on annealing temperature, TiO₂ nanotubes have shown different crystal forms; 100% anatase (0 % rutile), 18.4 % rutile (81.6 % anatase), 36.6 % rutile (63.4 % anatase) and 98.6% rutile (1.4% anatase). As the annealing temperature increases, the rutile ratio increases. OH radical generation from 18.4 % rutile TiO₂ nanotube plate was about 3.8 times higher than before annealing and 1.4 times higher than only 100 % anatase-TiO₂ nanotube. The efficiency of the 18.4% rutile TiO₂ nanotube was the best in comparison to TiO₂ nanotube with 18.4 %, 36.6 % and 98.6 % rutile. As a result, photocatalytic ability of 18.4 % rutile-TiO₂ nanotube plate was higher than 100 % anatase-TiO₂ nanotube plate.

TiO2 nanotube plate의 nanotube 형태에 따른 OH radical 생성량 평가

이용호,박대원 한국물환경학회 2016 한국물환경학회지 Vol.32 No.5

In this study, TiO2 nanotube was grown on a titanium plate by using anodic oxidation method for evaluation of TiO2 nanotube morphology. The TiO2 nanotube was grown in the electrolyte containing ethylene glycol, 0.2 wt% of NH4F and 2 vol% of H2O. Applied voltage was varied from 30 to 70 V and the morphology of TiO2 nanotube was observed. After anodization, TiO2 nanotube plate was immersed in 35 °C ethanol for 24 hours. Anatase and rutile crystal forms of TiO2 nanoutbe were observed after annealing. 4-chrolobenzoic acid, probe compound for OH radical was dissolved in H2O for measuring the OH radical. Liquid chromatography was used to check the concentration of 4-chrolobenzoic acid. OH radical generation by TiO2 nanotube plate is proportionate to the length of TiO2 nanotube. Furthermore, when the number of TiO2 nanotube plate increases, the OH radical generation is increasing too.

TiO₂ nanotube plate의 nanotube 형태에 따른 OH radical 생성량 평가

이용호 ( Yongho Lee ),박대원 ( Daewon Pak ) 한국물환경학회(구 한국수질보전학회) 2016 한국물환경학회지 Vol.32 No.5

In this study, a TiO₂ nanotube was grown on a titanium plate by using anodic oxidation method for the evaluation of TiO2 nanotube morphology. The TiO₂ nanotube was grown in an electrolyte containing ethylene glycol, 0.2 wt% of NH4F and 2 vol% of H₂O. Applied voltage varied from 30 to 70 V and the morphology of the TiO₂ nanotube was observed. After anodization, a TiO₂ nanotube plate was immersed in 35°C ethanol for 24 hours. Anatase and rutile crystal forms of TiO₂ nanoutbe were observed after annealing. 4-chrolobenzoic acid, a probe compound for OH radicals, was dissolved in H₂O in order to measure the OH radical. Liquid chromatography was used to check the concentration of the 4-chrolobenzoic acid. The OH radical generation by TiO₂ nanotube plate was proportionate to the length of the TiO₂ nanotube. Furthermore, when the number of TiO₂ nanotube plate increased, the OH radical generation increased as well.

Chemical State and Ultra-Fine Structure Analysis of Biocompatible TiO₂ Nanotube-Type Oxide Film Formed on Titanium Substrate

장재명,박수정,최갑송,권태엽,김교한 대한금속·재료학회 2008 METALS AND MATERIALS International Vol.14 No.4

TiO₂ nanotube-type oxide film on Ti substrate has been fabricated using an electrochemical method, and the chemical bonding state, ultra-fine structures, and surface characteristics of the TiO₂ nanotube layer have been investigated. The formation and growth of a self-organized nanotube layer can be achieved directly by anodization in NH4-containing electrolytes. The diameter, length, and wall thickness of the nanotube are significantly affected by anodizing conditions such as applied voltage, current density, and anodizing time. The length limiting factor of nanotube growth was found to be the diffusion of ionic species in the electrolyte. XRD investigations revealed that annealed nanotubes have anatase and rutile structure, and some Ti-peaks from the Ti substrate were observed. From the compositional analysis of TiO₂ nanotubes layer using Energy Dispersive Spectroscopy (EDS), Ti, O, and P elements were obtained in the wall nanotube layer. For incorporated P-containing in the TiO₂ nanotube layer, various chemical states were presented, which were revealed mostly in the forms of H₂PO₄, HPO₄²-, and PO₄³-. TiO₂ nanotube-type oxide film on Ti substrate has been fabricated using an electrochemical method, and the chemical bonding state, ultra-fine structures, and surface characteristics of the TiO₂ nanotube layer have been investigated. The formation and growth of a self-organized nanotube layer can be achieved directly by anodization in NH4-containing electrolytes. The diameter, length, and wall thickness of the nanotube are significantly affected by anodizing conditions such as applied voltage, current density, and anodizing time. The length limiting factor of nanotube growth was found to be the diffusion of ionic species in the electrolyte. XRD investigations revealed that annealed nanotubes have anatase and rutile structure, and some Ti-peaks from the Ti substrate were observed. From the compositional analysis of TiO₂ nanotubes layer using Energy Dispersive Spectroscopy (EDS), Ti, O, and P elements were obtained in the wall nanotube layer. For incorporated P-containing in the TiO₂ nanotube layer, various chemical states were presented, which were revealed mostly in the forms of H₂PO₄, HPO₄²-, and PO₄³-.

Improved osseointegration of dental titanium implants by TiO ₂ nanotube arrays with recombinant human bone morphogenetic protein-2: a pilot in vivo study

Lee, Jae-Kwan,Choi, Dong-Soon,Jang, Insan,Choi, Won-Youl Dove Medical Press 2015 INTERNATIONAL JOURNAL OF NANOMEDICINE Vol.10 No.-

<P>TiO<SUB>2</SUB> nanotube arrays on the surface of dental implants were fabricated by two-step anodic oxidation. Their effects on bone-implant contact were researched by a pilot in vivo study. The implants were classified into four groups. An implant group with TiO<SUB>2</SUB> nanotube arrays and recombinant human bone morphogenetic protein-2 (rhBMP-2) was compared with various surface implants, including machined surface, sandblasted large-grit and acid-etched surface, and TiO<SUB>2</SUB> nanotube array surface groups. The diameter of the TiO<SUB>2</SUB> nanotube window and TiO<SUB>2</SUB> nanotube were ~70 nm and ~110 nm, respectively. The rhBMP-2 was loaded into TiO<SUB>2</SUB> nanotube arrays and elution was detected by an interferometric biosensing method. A change in optical thickness of ~75 nm was measured by flow cell testing for 9 days, indicating elution of rhBMP-2 from the TiO<SUB>2</SUB> nanotube arrays. For the in vivo study, the four groups of implants were placed into the proximal tibia of New Zealand White rabbits. In the implant group with TiO<SUB>2</SUB> nanotube arrays and rhBMP-2, the bone-to-implant contact ratio was 29.5% and the bone volume ratio was 77.3%. Bone remodeling was observed not only in the periosteum but also in the interface between the bone and implant threads. These values were higher than in the machined surface, sandblasted large-grit and acid-etched surface, and TiO<SUB>2</SUB> nanotube array surface groups. Our results suggest that TiO<SUB>2</SUB> nanotube arrays could potentially be used as a reservoir for rhBMP-2 to reinforce osseointegration on the surface of dental implants.</P>

전류흐름에 따른 TiO₂ nanotube 광촉매의 OH radical 생성량 평가

김다은(Da Eun Kim),이용호(Yong Ho Lee),김대원(Dae Won Kim),박대원(Dae Won Pak) 한국유화학회 2017 한국응용과학기술학회지 Vol.34 No.2

본 연구에서는 TiO₂ nanotube 광촉매의 고도산화처리능을 비교하기 위해서 OH 라디칼 생성력을 평가하고자 하였다. 자외선 조사에 따른 Probe compound인 4-Chlorobenzoic acid (pCBA)의 농도 감소에 따라 OH radical 생성량을 산정하는 방법으로 광촉매 효율을 평가하였는데, TiO₂ nanotube 표면에서의 전자의 흐름을 원활하게 하기 위하여 전기적 에너지를 주었을 시 광촉매 효율의 증가 가능성 또한 확인하고자 자외선 조사 시 전류밀도를 인가하는 방법으로 실험을 진행하였다. 실험에 사용된 TiO₂ nanotube는 전극효과를 부여하기 위해 양극산화법으로 티타늄판을 이용하여 제조하였으며, pCBA용액에는 전도도를 부여하기 위하여 NaCl을 첨가하여 전해질로 사용하였다. 정전류 정전압 조건하에서 자외선조사 실험을 진행하였으며, 전류가 흐르는 광촉매에 자외선 조사 시 OH 라디칼 생성량은 광촉매 없이 자외선만 조사하였을 때에 비해 약 5.6배, TiO₂ 광촉매와 함께 자외선을 조사하였을 보다 약 2.2배 증가하였다. 결과적으로 광촉매반응에 전기적 에너지를 부여하였을 시 시너지효과를 가져올 수 있는 가능성을 확인할 수 있었다. OH radical generation is one of the common method to evaluate photocatalytic activity. In many of previous studies, only the UV(Ultraviolet) light was applied to test photocatalytic ability of TiO₂ nanotubes by studying probe compound(4-Chlorobenzoic acid) concentration change in solution. Also, TiO2 nanotubes were found to show some electrochemical characteristics when the flow of electric current was applied. In this study, the flow of electric current and UV light were applied at the same time to determine whether electrochemical characteristics of TiO₂ nanotube plate can give synergetic effect on the photocatalytic activity. TiO₂ nanotube was grown on Ti by anodic oxidation to create TiO₂ nanotube plate which can be used as a photocatalyst and a electrode that can undergo AOP(Advanced Oxidation Process) for water treatment. Probe compound solution was prepared using 4-chlorobenzoic acid and H₂O as a solvent. NaCl was added to give conductivity to work as electrolyte. As a result, enough level of electric current flow was found to give synergetic photocatalytic effect which can be used for efficient AOP water treatment method.

TiO2 nanotube plate를 이용한 전기적광촉매시스템의 염료폐수 처리 가능성 연구

이용호,쑨밍하오,박대원 한국물환경학회 2019 한국물환경학회지 Vol.35 No.5

In this study, TiO2 nanotubes with different morphologies were prepared in the electrolyte consisting of ethylene glycol, ammonium fluoride(NH4F), and deionized water(H2O) by controlling the voltage and time in the anodization method. Thicknesses and pore sizes of these TiO2 nanotubes were measured to interpret the relationship between anodization conditions and TiO2 nanotube morphologies. Element contents in the TiO2 nanotubes were detected for further analysis of TiO2 nanotube characteristics. Photoelectrolyticdecolorization efficiencies of the TiO2 nanotube plates with various morphologies were tested to clarify the morphology that a highly active TiO2 nanotube plate should have. Influences of applied voltage in photoelectrolysis processes and sodium sulfate(Na2SO4) concentration in wastewater on the decolorization efficiency were also studied. To save the equipment investment cost in photoelectrolysis methods, a two-photoelectrode system that uses the TiO2 nanotube plates as photoanode and photocathode instead of adding other counter electrodes was studied. Compared with single-photoelectrode system that uses the TiO2 nanotube plate as photoanode and titanium plate as cathode on the view of the treatment of dye wastewater containing different amounts of salt. As a result, a considerably suitable voltage was strictly needed for enhancing the photoelectrolyticdecolorization effect of the two-photoelectrode system but if salts exist in wastewater, an excellent increase in the decolorization efficiency can be obtained.