Photoelectrochemical properties of Fe₂O₃ nanorods grown with an Na₂SO₄ additive

Choi, Hayoung,Ryu, Hyukhyun,Lee, Won-Jae Elsevier 2018 Journal of industrial and engineering chemistry Vol.63 No.-

<P><B>Abstract</B></P> <P>Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrodes were grown using a microwave chemical bath deposition (MW-CBD) method with an Na<SUB>2</SUB>SO<SUB>4</SUB> additive at various concentrations. We investigated the effects of the Na<SUB>2</SUB>SO<SUB>4</SUB> additive concentration on the morphological, optical, structural, electrical, and photoelectrochemical properties of the Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrodes using scanning electron microscopy, ultraviolet-visible spectroscopy, X-ray diffraction, electrochemical impedance spectroscopy and potentiostat/galvanostat measurements, respectively. The Na<SUB>2</SUB>SO<SUB>4</SUB> concentration was found to affect the properties of the Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrodes, including the photoelectrochemical properties. Consequently, the highest photocurrent density value of 0.39mA/cm<SUP>2</SUP> was obtained from the sample prepared with an Na<SUB>2</SUB>SO<SUB>4</SUB> concentration of 0.03M.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrodes were grown via a microwave chemical deposition method using various Na<SUB>2</SUB>SO<SUB>4</SUB> concentrations. </LI> <LI> Na<SUB>2</SUB>SO<SUB>4</SUB> effects on morphological, optical, structural, electrical, and photoelectrochemical properties were investigated. </LI> <LI> The highest photocurrent density value of 0.39mA/cm2 was obtained from the sample with a Na<SUB>2</SUB>SO<SUB>4</SUB> concentration of 0.03M. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effects of ammonia in the synthesis of copper (II) oxide nanostructures grown via microwave chemical bath deposition

Lee, Suhun,Ryu, Hyukhyun,Lee, Won-Jae,Bae, Jong-Seong Elsevier 2018 Surface & coatings technology Vol.334 No.-

<P><B>Abstract</B></P> <P>In this study, CuO was grown on fluorine-doped tin oxide (FTO) substrates by depositing a copper (II) oxide seed layer via microwave chemical bath deposition while controlling the ammonia concentration. The morphological, optical, structural, electrical, and photoelectrochemical properties were measured by field emission scanning electron microscopy (FE-SEM), UV–vis spectroscopy (UV–vis), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and three-electrode potentiostat measurements, respectively. The ammonia concentration affected the morphological and structural properties (i.e., the growth and thickness of the CuO nanostructures), the optical properties (i.e., optical energy bandgap), the electrical properties (i.e., the flat-band potential and acceptor density) and the photoelectrochemical properties of the prepared CuO samples. As a result, the highest photocurrent density of 2.05mA/cm<SUP>2</SUP> (at −0.55V vs. SCE) was obtained for the sample with an ammonia concentration of 0.16M.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Copper(II) oxide nanostructures were grown on FTO substrates via a microwave chemical bath deposition method. </LI> <LI> The effects of ammonia concentration on the morphological, optical, and structural properties of CuO were analyzed. </LI> <LI> The photoelectrochemical properties of CuO were dependent on the thickness, flat-band potential, acceptor density. </LI> <LI> The highest photocurrent density of 2.05mA/cm<SUP>2</SUP> was obtained for the sample with an ammonia concentration of 0.16M. </LI> </UL> </P>

Improvement of an Al2O3/CuO heterostructure photoelectrode by controlling the Al2O3 precursor concentration

Suhun Lee,Hyukhyun Ryu,Won-Jae Lee,Jong Seong Bae 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.82 No.-

An Al2O3 capping layer was grown on a CuO photoelectrode using microwave-chemical bath deposition. We investigated the effects of the concentration of the Al2O3 precursor solution on the morphological,structural, optical, electrical and photoelectrochemical properties of the Al2O3/CuO heterostructurephotoelectrode. XPS analysis confirmed that the CuO was structurally stabilized by the Al2O3 cappinglayer. In addition, we found that the morphology, (020) XRD peak intensity, (020) XRD peak full width athalf maximum, optical energy band gap,flat-band potential and acceptor density values of the Al2O3/CuOheterostructure photoelectrode were strongly dependent on the concentration of the Al2O3 precursorsolution. Among the photoelectrodes evaluated in this study, the Al2O3/CuO heterostructurephotoelectrode obtained with an Al2O3 precursor concentration of 3 mM had the highest crystallinity,flat-band potential and acceptor density. It also exhibited a photocurrent density of -2.64 mA/cm2 (vs. SCEat0.55 V) and a photostability of approximately 55%. In contrast, bare CuO had a photocurrent densityof1.8 mA/cm2 (vs. SCE at0.55 V) and a photostability of 25%. Based on our results, the photocurrentdensity and photostability of the CuO photoelectrode could be dramatically improved by capping with anAl2O3 layer using a 3 mM precursor concentration.

Improved photostability of a CuO photoelectrode with Ni-doped seed layer

Oh, Jaejin,Ryu, Hyukhyun,Lee, Won-Jae,Bae, Jong-Seong Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.1

<P><B>Abstract</B></P> <P>In this study, we examined the growth of copper oxide (CuO) photoelectrodes using nickel-doped copper oxide seed layers with various doping concentrations. We investigated the effects of the seed layer doped with various amounts of nickel on the morphological, structural, optical and photoelectrochemical properties of the CuO photoelectrode by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and potentiostat/galvanostat measurements, respectively. We found that doping the seed layer with nickel affects properties such as the surface roughness, surface area, crystallinity and photostability. As a result, we obtained a maximum photostability of 46.2% using a 10at% nickel-doped seed layer.</P>

Effects of Urea as an Additive in Fe2O3 Thin‑Film Photoelectrodes

Yaejin Hong,Hyukhyun Ryu,Won-Jae Lee 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.6

In this study, an Fe2O3photoelectrode was grown on a fluorine-doped tin oxide substrate via microwave chemical bath deposition. We added various amounts of urea as an additive to the FeCl3precursor for the fabrication of the Fe2O3photoelectrodeand investigated the effects of the concentration of the urea additive on the morphological, optical, structural, electrical,and photoelectrochemical properties of this photoelectrode. Among the different concentrations evaluated, the maximumphotocurrent density (0.51 mA/cm2 at 0.6 V vs. SCE) was obtained using 0.05 M urea, as the resulting electrode had thegreatest thickness, highest flat-band potential, and preferential growth along the (110) plane along with favorable electrontransport characteristics. The maximum photocurrent density of the sample prepared with 0.05 M urea was approximately60% greater than that obtained from the sample prepared in the absence of urea. This study showed that the photoelectrochemicalproperties of the Fe2O3photoelectrode were substantially influenced by the changes in the morphological, optical,structural, and electrical properties caused by the addition of urea.

수열합성법으로 성장시킨 TiO₂ 나노로드의 형태학적, 구조적, 광전기화학적 특성 연구

최하영 ( Hayoung Choi ),류혁현 ( Hyukhyun Ryu ),이원재 ( Won-jae Lee ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.1

We investigated the effects of growth duration on the morphological, structural, and photoelectrochemical properties of TiO₂ nanorods grown on a TiO₂-buffered fluorine-doped tin oxide (FTO) substrate using the hydrothermal method. From the study, we found that the photoelectrochemical properties were mainly dependent on the nanorod length and (002) XRD peak intensity, which indicates vertical growth of the TiO₂. The morphological and structural properties of the TiO₂ nanorods largely affect their photoelectrochemical properties. The photocurrent density was increased when the growth duration was increased from 1 hour to 4 hours, and then changed little above 4 hours. Consequently, the highest photocurrent density, 0.897 mA/cm² (at 1.0 V vs. SCE), was obtained from the 8 hour-sample which had good morphological and structural properties. We used field emission scanning electron microscopy (FE-SEM) for analysis of the morphological properties, x-ray diffraction (XRD) for structural properties, and three-electrode potentiostat for photoelectrochemical properties. (Received April 7, 2016; Accepted July 7, 2016)

Photoelectrochemical properties of hematite thin films grown via a two-step electrochemical deposition method

Choi, Hayoung,Hong, Yaejin,Ryu, Hyukhyun,Lee, Won-Jae Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.4

<P><B>Abstract</B></P> <P>In this study, Fe<SUB>2</SUB>O<SUB>3</SUB> thin films were deposited via one-step and two-step electrochemical deposition methods. The one-step method used a constant growth potential, and the two-step method used two continuous growth potentials during the deposition. The morphological, electrical, and structural properties of the thin films and the relationships of each property with the photoelectrochemical properties of the thin films from the two methods were analyzed and compared. We determined that the samples grown by the two-step method have better photoelectrochemical properties than those grown by the one-step method. In this study, we attempted to determine the optimum growth potentials for the one-step and two-step methods and the growth durations of the first and second stages in the two-step method in terms of the photoelectrochemical properties. The sample formed at −0.05V for 30s in the first step and −0.25V for 2min 30s in the second step in the two-step method has the highest photocurrent density value of 0.28mA/cm<SUP>2</SUP> (at 0.5V vs. SCE), which is higher than that of the samples grown by the one-step method.</P>

Effects of annealing temperature on GO–Cu₂O composite films grown by electrochemical deposition for PEC photoelectrode

Kim, Tae Gyoum,Ryu, Hyukhyun,Lee, Won-Jae,Yoon, Jang-Hee Elsevier 2015 Current Applied Physics Vol.15 No.4

<P><B>Abstract</B></P> <P>In this work, graphene oxide–cuprous oxide (GO–Cu<SUB>2</SUB>O) composite films were grown on fluorine-doped tin oxide substrates by electrochemical deposition. We investigated the effects of the annealing temperature on the morphological, structural, optical and photoelectrochemical (PEC) properties of GO–Cu<SUB>2</SUB>O composite films. As a result, our work shows that while GO–Cu<SUB>2</SUB>O composite films exhibit the highest XRD (111) peak intensity at 300 °C sample, the highest photocurrent density value obtained was −4.75 mA/cm<SUP>2</SUP> at 200 °C sample (using 0.17 V versus a reversible hydrogen electrode (RHE)). In addition, a reduction reaction at 300 °C sample was observed using XPS analysis from the shift in the O1s peak in addition to a weaker O1s peak intensity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> GO–Cu<SUB>2</SUB>O composite films were grown by electrochemical deposition method. </LI> <LI> Effects of annealing temperature on GO–Cu<SUB>2</SUB>O composite films were investigated. </LI> <LI> The highest photocurrent density, −4.75 mA/cm<SUP>2</SUP>, was obtained from 200 °C sample. </LI> <LI> The co-existence of Cu<SUB>2</SUB>O and Cu phases by reduction decreased photocurrent density. </LI> </UL> </P>

Effects of Lithium (Li) on Lithium-cuprous-oxide (Li-Cu2O) Composite Films Grown by Using Electrochemical Deposition for a PEC Photoelectrode

Tae Gyoum Kim,Hyukhyun Ryu,Won-Jae Lee 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.2

In this study, Li-Cu2O composite films were grown on fluorine-doped tin-oxide (FTO) substrates by using the electrochemical deposition method. Various amounts of lithium (Li) were added to grow the Li-Cu2O composite films. We analyzed the morphology, structure, photocurrent density and photo-stability of the Li-Cu2O composite films by using various measurements such as field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and potentiostat/galvanostat measurements, respectively. As a result, the highest XRD Cu2O (111)/ LiO (011) peak intensity ratio was obtained for the 10-wt% sample, which also had the highest photocurrent density value of −5.00 mA/cm2 . The highest photocurrent density value for the 10-wt% sample was approximately 5 times greater than that of the 0-wt% sample. As shown by this result, we found that adding Li could improve the photocurrent values of Li-Cu2O composite films.

Photoelectrochemical properties of hematite thin films grown by MW-CBD

Choi, Hayoung,Hong, Yaejin,Ryu, Hyukhyun,Lee, Won-Jae Elsevier 2018 Surface & coatings technology Vol.333 No.-

<P><B>Abstract</B></P> <P>In this study, Fe<SUB>2</SUB>O<SUB>3</SUB> thin films were grown on a Fe<SUB>2</SUB>O<SUB>3</SUB> buffered-film using the microwave chemical bath deposition (MW-CBD) method with different FeCl<SUB>3</SUB> precursor concentrations. The morphological, optical, structural, electrical and photoelectrochemical properties of the Fe<SUB>2</SUB>O<SUB>3</SUB> thin films were studied according to the different precursor concentrations, and the relationships between each property were systematically analyzed. From the study, we found that the morphological, structural and electrical properties greatly influenced the photoelectrochemical properties. As a result, the 0.1M sample, which has good morphological, structural, and electrical properties has the highest photocurrent density value of 0.31mA/cm<SUP>2</SUP> (at 0.5V vs. SCE), and has good photostability properties. Field emission scanning electron microscopy (FE-SEM) and atomic force microscope (AFM) were used to characterize the morphological properties of the Fe<SUB>2</SUB>O<SUB>3</SUB> thin films. X-ray diffraction (XRD) was used to study the structural properties, UV–visible spectroscopy was used to measure the optical properties, electrochemical impedance spectroscope (EIS) was used to characterize the electrical properties and a three-electrode potentiostat was used to measure the photoelectrochemical properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrode was grown by microwave chemical deposition (MW-CBD) method. </LI> <LI> The effects of the FeCl<SUB>3</SUB> concentration on the Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrode were investigated. </LI> <LI> The properties of Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrode were largely dependent on the FeCl<SUB>3</SUB> concentration. </LI> <LI> The 0.1 M-sample had the best photoelectrochemical properties. </LI> </UL> </P>