Potentiodynamic Electrodeposition of CoSe₂ Films and Their Excellent Electrocatalytic Activity as Counter Electrodes for Dye-Sensitized Solar Cells

Quy, Vu Hong Vinh,Park, Jeong-Hyun,Kang, Soon-Hyung,Kim, Hyunsoo,Ahn, Kwang-Soon Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.10

<P>Cobalt selenide (CoSe<SUB>2</SUB>) thin films are successfully formed on F-doped SnO<SUB>2</SUB> (FTO) via a single step potentiodynamic electrodeposition process without any post treatment, and are utilized as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The electrochemical behavior of the electrodeposited FTO/CoSe<SUB>2</SUB> films is examined through Tafel polarization, cyclic voltammetry, and electrochemical impedance spectroscopy measurements. The results indicate that the FTO/CoSe<SUB>2</SUB> films exhibit outstanding electrocatalytic ability and electrochemical stability toward the I<SUP>−</SUP>/I<SUP>−</SUP><SUB>3</SUB> redox couple. The optimized FTO/CoSe<SUB>2</SUB> film fully covers the FTO substrate and features a nanoporous structure of interconnecting nanocrystalline networks, which is beneficial for the diffusion of ions and provides numerous electrochemical active sites. The optimized DSSC using FTO/CoSe<SUB>2</SUB> as CE exhibits a significantly improved cell efficiency of 7.95% compared to that of the DSSC using FTO/Pt as CE (7.48%).</P>

Electrodeposited MoS₂ as electrocatalytic counter electrode for quantum dot- and dye-sensitized solar cells

Quy, Vu Hong Vinh,Vijayakumar, Elayappan,Ho, Phuong,Park, Jeong-Hyun,Rajesh, John Anthuvan,Kwon, JongMyeong,Chae, Jiyoung,Kim, Jae-Hong,Kang, Soon-Hyung,Ahn, Kwang-Soon Elsevier 2018 ELECTROCHIMICA ACTA Vol.260 No.-

<P><B>Abstract</B></P> <P>Molybdenum disulfide (MoS<SUB>2</SUB>) films are electrochemically synthesized on F-doped SnO<SUB>2</SUB> (FTO) substrates using potentiostatic electrodeposition (ED) at a constant −1 V for 20–60 min. The MoS<SUB>2</SUB> is deposited according to island growth mode. As the ED time increases to 40 min, the clusters of MoS<SUB>2</SUB> nano particles enlarge and thicken, but maintain nanopores between the clusters. Additional increase in ED time (to 60 min) causes clusters to merge and make the film denser. Furthermore, this MoS<SUB>2</SUB> film exhibits cracks due to stress accumulated in the film. The film FTO/MoS<SUB>2</SUB> (40 min) shows significantly enhanced electrocatalytic activity compared to other films. This is because the FTO/MoS<SUB>2</SUB> (40 min) not only has more electrochemically active sites but also significantly facilitates charge transfer and mass transport. When it is employed as the counter electrode (CE) for quantum-dot and dye-sensitized solar cells (QD-SSC, D-SSC), the QD-SSC with FTO/MoS<SUB>2</SUB> (40 min) CE exhibits even higher overall energy conversion cell efficiency (3.69%) than that with Pt CE (2.16%). Moreover, the D-SSC with FTO/MoS<SUB>2</SUB> (40 min) CE exhibits cell efficiency (7.16%) similar to that with FTO/Pt CE (7.48%). This indicates that MoS<SUB>2</SUB> is a promising CE for all QD-SSCs and D-SSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB> films were electrochemically synthesized on F-doped SnO<SUB>2</SUB> substrates. </LI> <LI> Change in electrodeposition time affected particle size and pore condition. </LI> <LI> FTO/MoS<SUB>2</SUB> -ED 40 min had better electrocatalytic activity and more active sites. </LI> <LI> FTO/MoS<SUB>2</SUB> -40 also showed much improved charge transfer and mass transport. </LI> <LI> FTO/MoS<SUB>2</SUB>-40 CEs in QD-SSC and D-SSC showed better efficiency than Pt CE. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

One-Step Electrodeposited Nickel Cobalt Sulfide Electrocatalyst for Quantum Dot-Sensitized Solar Cells

Quy, Vu Hong Vinh,Min, Bong-Ki,Kim, Jae-Hong,Kim, Hyunsoo,Rajesh, John Anthuvan,Ahn, Kwang-Soon The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.5

<P>This paper reports a new facile one-step cyclic voltammetry electrochemical co-depositing method to prepare a novel nickel cobalt sulfide (NiCo2S4) counter electrode (CE) on a FTO glass substrate as well as its promising application as an efficient CE in CdSe quantum dot-sensitized solar cells (QD-SSCs). The QD-SSCs fabricated using NiCo2S4 as a CE exhibited a significantly enhanced short circuit current and fill factor, resulting in a significantly improved overall energy conversion efficiency (3.67%) compared to those with the Pt (2.26%), CoS (2.70%) and NiS (2.56%) CEs under 1 sun illumination. This can be attributed to the significantly enhanced electrocatalytic activity and superior electrical conductivity of the NiCo2S4 and the excellent electrical contact at the electrodeposited NiCo2S4/FTO interface. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Improved electrocatalytic activity of electrodeposited Ni3S4 counter electrodes for dye- and quantum dot-sensitized solar cells

Vu Hong Vinh Quy,박정현,강순형,김현수,안광순 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.70 No.-

Nickel sulfide (Ni3S4)films are deposited onto F-doped SnO2 (FTO) substrates using a facile one-steppotentiodynamic electrodeposition without any extra treatment. The potential sweep is between0.9 Vand 0.7 V (vs. Ag/AgCl) for 4–10 cycles. The series resistance is gradually reduced with increased Ni3S4film thickness, indicating the metallic conduction of the Ni3S4 phase. The Ni3S4 deposited for 8 cycles(denoted FTO/Ni3S4-8) exhibits full coverage on the FTO substrate, with 110 nm thickness and adistinctive structure of porous and nanoscale interconnecting nanoparticular networks, which providenumerous electrochemical active sites to contact with electrolyte. Thefilm not only exhibits prominentelectrocatalytic activities but also shows excellent electrochemical stability in both polysulfide andiodide-based electrolytes compared to FTO/Pt. On the contrary, the FTO/Ni3S4-10 shows merged clusters,leading to more compact and less porous morphology, which reduced electrocatalytic activity. Thequantum dot-sensitized solar cell (QD-SSC) fabricated using the FTO/Ni3S4-8 counter electrode (CE)exhibits power conversion efficiency (PCE) of 4.57%, short-circuit current (Jsc) of 15.92 mA cm 2,open-circuit voltage (Voc) of 0.545 V, andfill factor (FF) of 52.63%. In addition, the dye-sensitized solar cell(D-SSC) using FTO/Ni3S4-8 CE achieves a PCE of 8.17%, Jsc of 16.28 mA cm 2, Voc of 0.735 V, and FF of68.34%. On the other hand, the PCEs of 2.56% and 7.58% are obtained for QD-SSC and D-SSC with Pt CE,respectively. We suggest that the electrodeposited Ni3S4 should be promising electrocatalytic electrodesfor various applications such as QD-SSCs, D-SSCs, supercapacitors, photoelectrochemical water-splittingcells, and batteries.

Improved electrocatalytic activity of electrodeposited Ni₃S₄ counter electrodes for dye- and quantum dot-sensitized solar cells

Quy, Vu Hong Vinh,Park, Jeong-Hyun,Kang, Soon-Hyung,Kim, Hyunsoo,Ahn, Kwang-Soon Elsevier 2019 Journal of industrial and engineering chemistry Vol.70 No.-

<P><B>Abstract</B></P> <P>Nickel sulfide (Ni<SUB>3</SUB>S<SUB>4</SUB>) films are deposited onto F-doped SnO<SUB>2</SUB> (FTO) substrates using a facile one-step potentiodynamic electrodeposition without any extra treatment. The potential sweep is between −0.9V and 0.7V (vs. Ag/AgCl) for 4–10 cycles. The series resistance is gradually reduced with increased Ni<SUB>3</SUB>S<SUB>4</SUB> film thickness, indicating the metallic conduction of the Ni<SUB>3</SUB>S<SUB>4</SUB> phase. The Ni<SUB>3</SUB>S<SUB>4</SUB> deposited for 8 cycles (denoted FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-8) exhibits full coverage on the FTO substrate, with 110nm thickness and a distinctive structure of porous and nanoscale interconnecting nanoparticular networks, which provide numerous electrochemical active sites to contact with electrolyte. The film not only exhibits prominent electrocatalytic activities but also shows excellent electrochemical stability in both polysulfide and iodide-based electrolytes compared to FTO/Pt. On the contrary, the FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-10 shows merged clusters, leading to more compact and less porous morphology, which reduced electrocatalytic activity. The quantum dot-sensitized solar cell (QD-SSC) fabricated using the FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-8 counter electrode (CE) exhibits power conversion efficiency (PCE) of 4.57%, short-circuit current (J<SUB>sc</SUB>) of 15.92mAcm<SUP>−2</SUP>, open-circuit voltage (V<SUB>oc</SUB>) of 0.545V, and fill factor (FF) of 52.63%. In addition, the dye-sensitized solar cell (D-SSC) using FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-8 CE achieves a PCE of 8.17%, J<SUB>sc</SUB> of 16.28mAcm<SUP>−2</SUP>,V<SUB>oc</SUB> of 0.735V, and FF of 68.34%. On the other hand, the PCEs of 2.56% and 7.58% are obtained for QD-SSC and D-SSC with Pt CE, respectively. We suggest that the electrodeposited Ni<SUB>3</SUB>S<SUB>4</SUB> should be promising electrocatalytic electrodes for various applications such as QD-SSCs, D-SSCs, supercapacitors, photoelectrochemical water-splitting cells, and batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni<SUB>3</SUB>S<SUB>4</SUB> films were electrochemically synthesized on F-doped SnO<SUB>2</SUB> substrates. </LI> <LI> FTO/Ni<SUB>3</SUB>S<SUB>4</SUB> exhibited porous and nanoscale interconnecting nanoparticular networks. </LI> <LI> FTO/Ni<SUB>3</SUB>S<SUB>4</SUB> provided excellent electrocatalytic activity and numerous active sites. </LI> <LI> It led to significantly enhanced charge transfer and mass transport kinetics. </LI> <LI> FTO/Ni<SUB>3</SUB>S<SUB>4</SUB> CE showed better performance than Pt CE for both of QD-SSC and D-SSC. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

One-step electrodeposited Ni₃S₄ as efficient counter electrodes for dye-sensitized solar cells

채지영,( Vu Hong Vinh Quy ),안광순 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Dye-sensitized solar cell (D-SSC) is composed of a dye-sensitized TiO2 photo-anode, an electrolyte containing the iodide/tri-iodide redox couple, and a counter electrode. As an important part in D-SSC, the counter electrode (CE) is responsible for electron transfer from the external circuit back to the redox couple and catalyzing the reduction reaction of the I3^- species in the electrolyte. The use of conventional Pt-based CEs reveals critical issues such as high cost, relative scarcity, and the requirement for mandatory high-temperature calcination. Herein, for the first time, Ni₃S₄ was synthesized and deposited on the FTO substrate using the facile potentiodynamic electrodeposition. The prepared FTO/Ni₃S₄ electrode exhibited an excellent chemical stability toward I^-/I3^- redox electrolyte and displayed the significantly enhanced electrocatalytic activity, resulting in much higher cell efficiency (8.17 %), as compared to Pt CE (7.58 %), when applied to N719-based D-SSCs.

Preparation of copper sulfide electrocatalyst using electrodeposited Cu-Zn alloy for quantum dot-sensitized solar cells

채지영,( Vu Hong Vinh Quy ),( Elayappan Vijayakumar ),( Anthuvan Rajesh ),안광순 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Quantum dot-sensitized solar cells (QDSSCs) are a reliable renewable energy source. A QDSSC is assembled with the components in the following order: FTO/TiO2/QD/polysulfide electrolyte/CE/FTO. Recently, multiple efforts have been made to increase the power conversion efficiency of by modifying the materials by optimize chemical and physical properties. In QDSSCs, the counter electrodes (CEs) plays a key role in completing the electrical circuit and in the regeneration of sulfur redox couple through a reduction process. Among the CE materials, copper(I) sulfide (Cu2S) is a promising alternative to Pt CE, primarily due to its favorable electrochemical properties in the S2-/Sn2- redox couple, low cost, and high stability compared to other. In this study, we have reported Cu2S CE deposited Cu-Zn alloy on FTO and removed Zn using HCl after sulfurization. We simply increased surface area of CEs by removing Zn. These samples exhibited better electrocatalytic activity than FTO/Cu2S CEs.

Enhanced Electrocatalytic Activity of Cu₂S-Polyaniline Heterostructure Counter Electrode for Quantum Dot-Sensitized Solar Cells

Vijayakumar, Elayappan,Quy, Vu Hong Vinh,Kwon, JongMyeong,Chae, Jiyoung,Kim, Jae-Hong,Kang, Soon-Hyung,Kim, Hyunsoo,Ahn, Kwang-Soon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.12

<P>The Cu2S-Polyaniline (Cu-P) counter electrode (CE) was prepared by electropolymerization of polyaniline (PANI) on a FTO/Cu2S film. The surface morphology and crystallinity of the counter electrode were examined. The FTO/Cu-P CE provided significantly enhanced electrochemical activity and a faster charge transfer rate compared to the platinum (Pt), Cu2S, PANI, and PANI-Cu2S (P-Cu) CEs because of the synergistic effect between the high carrier mobility of PANI and the good electrocatalytic activity of Cu2S on the polysulfide electrolyte. Besides, the FTO/Cu-P CE exhibited excellent electrochemical stability, due to the strong interaction between the metal particles and electronegative nitrogen of PANI. The quantum dot-sensitized solar cell (QDSSC) with the FTO/Cu-P heterostructure CE exhibited a higher energy conversion efficiency (4.12%) than those with Pt (1.85%), Cu2S (3.71%), PANI (0.77%), and PANI-Cu2S (P-Cu) (1.01%) CEs. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Enhanced electrocatalytic activity and electrochemical stability of copper(I) sulfide electrode electrodeposited on a Ti interlayer-coated fluorine-doped tin oxide substrate and its application to quantum dot-sensitized solar cells

Chae, Jiyoung,Oh, Munsik,Quy, Vu Hong Vinh,Kwon, JongMyeong,Kim, Jae-Hong,Kang, Soon-Hyung,Kim, Hyunsoo,Vijayakumar, Elayappan,Ahn, Kwang-Soon Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-

<P><B>Abstract</B></P> <P>Copper(I) sulfide (Cu<SUB>2</SUB>S) films are deposited on 15 nm-thick Ti (Titania) interlayer-coated fluorine-doped tin oxide (FTO) substrates. This is performed using potentiodynamic electrodeposition at selective numbers of cycles (10−20) in the potential range of −0.7 V to −0.2 V (vs. Ag/AgCl), followed by sulfurization. The results of Cu<SUB>2</SUB>S films on the FTO/Ti substrates are subsequently employed as counter electrodes for cadmium selenide quantum dot-sensitized solar cells (QDSSC). The Ti interlayer facilitates the Cu (copper) nucleation, during the Cu electrodeposition and leads to side-by-side packing of small Cu<SUB>2</SUB>S nanosheets after sulfurization. In contrast, conventional Cu<SUB>2</SUB>S grown on the FTO consists of a mixture of large and small Cu<SUB>2</SUB>S nanosheets. The distinct nanostructure of the FTO/Ti/Cu<SUB>2</SUB>S counter electrodes enhances the electrocatalytic activity and electrochemical stability comparing to those of FTO/Pt (Platinum) and FTO/Cu<SUB>2</SUB>S films. This is due to the increased number of electrochemically active sites, fast ion transport in the Cu<SUB>2</SUB>S nanosheets perpendicular to the substrate, and good adhesion to the Ti interlayer. The optimized FTO/Ti/Cu<SUB>2</SUB>S electrode, deposited in 15 cycles, contributes to significantly increase the cell efficiency (4.11%) of the QDSSC, resulting in 140% and 35.2% performances improvements for the QDSSCs with the Pt (1.71%) and FTO/Cu<SUB>2</SUB>S (3.04%) counter electrodes, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu<SUB>2</SUB>S prepared by electrochemical deposition on Ti interlayer-coated FTO. </LI> <LI> Ti interlayer facilitates the uniform Cu nucleation growth with small size. </LI> <LI> FTO/Ti/Cu<SUB>2</SUB>S (15 cycle) show excellent electrocatalytic activity and stability. </LI> <LI> QDSSC with the FTO/Ti/Cu<SUB>2</SUB>S exhibits significantly enhanced cell performance. </LI> </UL> </P>

Rambutan-like cobalt nickel sulfide (CoNi2S4) hierarchitecture for high-performance symmetric aqueous supercapacitors

John Anthuvan Rajesh,박정현,Vu Hong Vinh Quy,권종명,최지영,강순형,김현수,안광순 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.63 No.-

A novel hierarchical cobalt nickel sulfide (CoNi2S4) nanostructure resembling the rambutan fruit was obtained by a simple one-step hydrothermal method using ethylene glycol as the solvent. Scanning and transmission electron microscopic analyses revealed that the as-synthesized CoNi2S4 consists of numerous hairy nanorods grown radially on top of individual sphere-like core structures. The CoNi2S4 hierarchical material was applied as a potential electrode for supercapacitors in both three- and two-electrode systems. The hairy nanorods and spheres were highly interconnected to form hierarchical rambutan-like CoNi2S4 structure with increased active areas of the electrode, and this facilitate effective charge transport from the nanorods to the spherical core structure. When evaluated as an electrode material in a three-electrode system, CoNi2S4 with the hierarchical structure delivered a high specific capacitance of 1102.22 F g−1 at a current density of 1 A g−1 with excellent rate capability (68.55% capacitance retention as the current increases from 1 to 10 A g−1) and significant cycling stability (75% retention after 3000 cycles). The electrochemical properties of the hierarchical CoNi2S4 were also investigated in a symmetrical cell arrangement using 2 M aqueous KOH as the electrolyte. The symmetric aqueous supercapacitor exhibited a specific capacitance of 482 F g−1 at 1 A g−1 with maximum energy density of 16.74 Wh kg−1 and maximum power density of 10.2 kW kg−1. Furthermore, the symmetric supercapacitor exhibited excellent cycling stability, showing 92.85% capacitance retention even after 5000 cycles.