Prototype electrochromic device and dye sensitized solar cell using spray deposited undoped and 'Li' doped V₂O₅ thin film electrodes

Kovendhan, M.,Paul Joseph, D.,Manimuthu, P.,Sendilkumar, A.,Karthick, S.N.,Sambasivam, S.,Vijayarangamuthu, K.,Kim, H.J.,Choi, B.C.,Asokan, K.,Venkateswaran, C.,Mohan, R. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.5

Lithium (Li) (0-5 wt%) doped V<SUB>2</SUB>O<SUB>5</SUB> thin films were spray deposited at 450 <SUP>o</SUP>C onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V<SUB>2</SUB>O<SUB>5</SUB> phase, presence of VO<SUB>2</SUB> peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V<SUB>2</SUB>O<SUB>5</SUB> samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V<SUB>2</SUB>O<SUB>5</SUB> thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V<SUB>2</SUB>O<SUB>5</SUB> film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V<SUB>2</SUB>O<SUB>5</SUB> thin film to demonstrate the colour change.

Prototype electrochromic device and dye sensitized solar cell using spray deposited undoped and ‘Li’ doped V2O5 thin film electrodes

M. Kovendhan,D. Paul Joseph,P. Manimuthu,A. Sendilkumar,S.N. Karthick,S. Sambasivam,K. Vijayarangamuthu,김희제,최병춘,K. Asokan,C. Venkateswaran,R. Mohan 한국물리학회 2015 Current Applied Physics Vol.15 No.5

Lithium (Li) (0-5 wt%) doped V2O5 thin films were spray deposited at 450 ℃ onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V2O5 phase, presence of VO2 peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V2O5 samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V2O5 thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V2O5 film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V2O5 thin film to demonstrate the colour change.

Alternative cost-effective electrodes for hydrogen production in saline water condition

Kovendhan, M.,Kang, Hari,Youn, Jong Sang,Cho, Hyunwook,Jeon, Ki-Joon Elsevier 2019 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.44 No.11

<P><B>Abstract</B></P> <P>For the sustainable clean and green energy, hydrogen is considered as one of the prominent renewable energy source which attracted increasing interests in recent years. To produce this, one of the cheapest method is water electrolysis. But several challenges in water electrolysis are, to reduce the maintenance cost, energy consumption and high cost of platinum electrode material. So, in search of an alternative low cost and efficient electrode material, researchers are modifying various metals electrodes to replace the noble metal electrodes. Stainless steel (SS 304) is one of the types of carbon steel material commonly used for various applications. The aim of the work is to explore the stainless steel (SS 304), annealed at high temperature, with and without “hydrogen and argon” environment and tested the samples for hydrogen production in sea water condition (3.5% NaCl). Cr<SUB>2</SUB>O<SUB>3</SUB> and MnCr<SUB>2</SUB>O<SUB>4</SUB> spinel oxide formation was observed over the surface of the electrodes after annealing process. From Raman, X-ray Photoelectron Spectroscopy (XPS) and electrochemical measurements it was observed that, the sample prepared under hydrogen and argon environment is stable when compared with the rest of the samples. Decrease in relative amount of chromium oxide was observed for the sample annealed in air environment. The rate of production of hydrogen prepared under “hydrogen and argon” environment is higher and the results are discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Raman peaks at 550 cm<SUP>−1</SUP> and 640 cm<SUP>−1</SUP> for annealed sample, belongs to Cr<SUB>2</SUB>O<SUB>3</SUB> and MnCr<SUB>2</SUB>O<SUB>4</SUB> spinel respectively. </LI> <LI> Disordered hexagonal shaped, non-uniform, twisted oxide grain growth with pores and defects are observed. </LI> <LI> The Mn in the presence of oxygen supresses the growth of Cr<SUB>2</SUB>O<SUB>3</SUB> in the case of air annealed sample. </LI> <LI> The “H<SUB>2</SUB> and Ar” annealed sample looks highly stable and produces more hydrogen when compared with the rest. </LI> </UL> </P>

Study of stainless steel electrodes after electrochemical analysis in sea water condition

Kovendhan, M.,Kang, Hari,Jeong, Sangmin,Youn, Jong-Sang,Oh, Inhwan,Park, Young-Kwon,Jeon, Ki-Joon Academic Press 2019 Environmental research Vol.173 No.-

<P><B>Abstract</B></P> <P>For water electrolysis, a rare earth material (eg., platinum) is often used as an electrode, but because of the high cost and toxicity of chemicals, researchers are searching for cost effective and eco-friendly alternative materials. Various alloys and metals have been long explored for use as electrode materials in different media. Stainless steel (SS 304) electrodes are cost effective and have a large surface area; further their catalytic performance is comparable to that of carbon coated noble metals cathodes. Stainless steel has good mechanical properties and durability so it is widely used in desalination plants, oil and gas industries, ship building, etc. However, over a period of time it corrodes very quickly in saline water. To improve the stability and durability of the electrodes (i.e., to minimize corrosion), we anneal the samples under two different sets of conditions and test the electrodes in 3.5% NaCl solution. The anodic peak (−0.25 V) observed for bare stainless steel result from the formation of iron (II) hydroxide [Fe(OH)<SUB>2</SUB>]. The Raman bands observed at 210 and 274 cm<SUP>−1</SUP> for bare stainless steel result from the formation of α-Fe<SUB>2</SUB>O<SUB>3</SUB> owing to partial, anodic, and cathodic reactions occurring on the electrode which disrupts the surface layers. High intensity X-ray diffraction (XRD) and Raman peaks of Cr<SUB>2</SUB>O<SUB>3</SUB> and MnCr<SUB>2</SUB>O<SUB>4</SUB> observed in argon and hydrogen annealed sample after cyclic voltammetry reveal that this sample is more stable than bare and air annealed samples. XRD reveals mixed oxide phases in addition to eskolaite and magnetite phases. Scanning electron microscope (SEM) images show that although the air-annealed sample has a soft, spongy structure, Na and Cl ions are adsorbed in the voids on the outer surface of the electrode leading to quick degradation. For the air-annealed sample the oxide appears to adhere poorly to the stainless steel. Oxygen (ie., oxide composition) may play a key role in adherence and growth of Cr<SUB>2</SUB>O<SUB>3</SUB> formed at high temperature. X-ray photoelectron spectroscopy (XPS) reveals that large amounts of Cr and Mn are dissolved/corroded into the electrolyte for air annealed sample which is in good agreement with the Raman and SEM results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The anodic peak (−0.25 V) observed in bare stainless steel (BS) is due to the formation of iron (II) hydroxide (Fe(OH)<SUB>2</SUB>). </LI> <LI> For bare stainless steel due to NaCl adsorption elongation of a large number of pits and patches was observed from SEM image. </LI> <LI> Air Annealed sample corrodes very quickly due to the presence of high amount of oxygen. </LI> <LI> XRD and Raman confirmed the sample annealed in “argon and hydrogen” environment is highly stable. </LI> <LI> The adsorption intensity of NaCl decreased and follows the trend RE > AA sample. </LI> </UL> </P>

해수 조건에서 수소 생산을 위한 효과적인 가격으로 대체 가능한 전극

강하리,M. Kovendhan,Le Thi Hoang Yen,박선영,정용원,전기준 한국대기환경학회 2018 한국대기환경학회 학술대회논문집 Vol.2018 No.10

친환경 MoS₂/Graphene 기반 나노촉매 개발 및 수소생산 특성 평가

한은지,M. Kovendhan,남주현,정용원,전기준 한국대기환경학회 2017 한국대기환경학회 학술대회논문집 Vol.2017 No.11

Tailoring the properties of spray deposited V₂O₅ thin films using swift heavy ion beam irradiation

Rathika, R.,Kovendhan, M.,Joseph, D. Paul,Pachaiappan, Rekha,Kumar, A. Sendil,Vijayarangamuthu, K.,Venkateswaran, C.,Asokan, K.,Jeyakumar, S. Johnson Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.11

Swift heavy ion (SHI) beam irradiation can generate desirable defects in materials by transferring sufficient energy to the lattice that favours huge possibilities in tailoring of materials. The effect of Ag¹⁵⁺ ion irradiation with energy 200 MeV on spray deposited V₂O₅ thin films of thickness 253 nm is studied at various ion doses from 5 × 10¹¹ to 1 × 10¹³ ions/㎠. The XRD results of pristine film confirmed orthorhombic structure of V₂O₅ and its average crystallite size was found to be 20 nm. The peak at 394 cm^-1 in Raman spectra confirmed O-V-O bonding of V₂O₅, whereas 917 cm^-1 arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 10¹² ions/㎠. Optical studies by UV-Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 10¹² ions/㎠. The red shift is observed both in the direct and indirect band gaps until 5 × 10¹² ions/㎠. The surface topography of the pristine film revealed sheath like structure with randomly distributed spherical nano-particles. The roughness of film decreased and the density of spherical nanoparticles increased upon irradiation. Irradiation improved the conductivity significantly for fluence 5 × 10¹¹ ions/㎠ due to band gap reduction and grain growth.

200 MeV Ag 15+ ion beam irradiation induced modifi cations in spray deposited MoO 3 thin films by fl uence variation

R. Rathika,M. Kovendhan,D. Paul Joseph,K. Vijayarangamuthu,A. Sendil Kumar,C. Venkateswaran,K. Asokan,S. Johnson Jeyakumar 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Spray deposited Molybdenum trioxide (MoO3) thin film of thickness nearly 379 nm were irradiated with 200 MeV Ag15þ ion beam at different fluences (Ø) of 5 1011,1 1012,5 1012 and 1 1013 ions/cm2. The X-ray diffraction (XRD) pattern of the pristine film confirms orthorhombic structure and the crys-tallinity decreased after irradiation with the fluence of 5 1011 ions/cm2 due to irradiation induced defects and became amorphous at higher fluence. In pristine film, Raman modes at 665, 820, 996 cm1 belong to MoeO stretching, 286 cm1 belong to MoeO bending mode and those below 200 cm1 are associated with lattice modes. Raman peak intensities decreased upon irradiation and vanished completely for the ion fluence of 5 1012 ions/cm2. The percentage of optical transmittance of pristine film was nearly 40%, while for irradiated films it decreased significantly. Red shift was observed for both the direct and indirect band gaps. The pristine film surface had densely packed rod like structures with relatively less porosity. Surface roughness decreased significantly after irradiation. The electrical trans-port properties were also studied for both the pristine and irradiated films by Hall effect. The results are discussed.

Optimization of Zn₂SnO₄ thin film by post oxidation of thermally evaporated alternate Sn and Zn metallic multi-layers

R., Ramarajan,M., Kovendhan,Phan, Duy-Thach,K., Thangaraju,R., Ramesh Babu,Jeon, Ki-Joon,D., Paul Joseph Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.449 No.-

<P><B>Abstract</B></P> <P>An attempt to optimize Zn<SUB>2</SUB>SnO<SUB>4</SUB> (ZTO) thin film has been done by alternate thermal evaporation of ‘Sn’ and ‘Zn’ in the sequence Sn10/Zn15/Sn15/Zn15/Sn5 onto corning glass substrates and subsequent post oxidation process. The XRD patterns of as-deposited metallic thin films changed over from metallic to oxidized ZTO phase with cubic spinel structure along with ZnO phase. The film thickness and roughness increased apparently due to diffusion of oxygen into the metallic inter-layers. The binding energies estimated from the XPS data also indicated oxidation of the metallic multi-layers. Post-annealing of the film developed transparency in visible region to around 40%. The direct band gap of ZTO and ZnO were estimated to be 3.46 eV and 3.10 eV respectively. The annealed ZTO thin film was measured for electrical transport parameters by Hall Effect measurement. Raman spectrum observed at 668 cm<SUP>−1</SUP> is due to stretching vibration of short metal-oxide bonds in the MO<SUB>6</SUB> octahedron. The photoluminescence spectrum showed blue emission centered around 436 nm predominantly due to oxygen vacancies in addition to weak orange emission centered at 625 nm. Gas sensor using thin films of as-deposited and ZTO formed by post-annealing process showed significant sensing response for NO<SUB>2</SUB> gas. These results reveal that the ZTO thin film deposited by alternate thermal evaporation and subsequent post oxidation is worth exploring as transparent conducting electrode and also as a gas sensing material.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Metallic Sn and Zn were deposited by a newer alternate evaporation in Sn10/Zn15/Sn15/Zn15/Sn5 sequence. </LI> <LI> Upon annealing, metallic multi-layers gets intermixed and oxidized leading to Zn<SUB>2</SUB>SnO<SUB>4</SUB> phase. </LI> <LI> Transparency in visible region was around 40% with 3.46 eV direct band gap value. </LI> <LI> The PL emission has a broad asymmetric peak in blue region due to free-to-bound recombination. </LI> <LI> The annealed film has a response/recovery time of 51/107 s for 50 ppm of NO<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation of ultra-thin and flexible Au–Ag–Au transparent conducting electrode

Ch Surya Prakasarao,Pratim Hazarika,Slavia Deeksha DSouza,Jean Maria Fernandes,M. Kovendhan,R. Arockia Kumar,D. Paul Joseph 한국물리학회 2020 Current Applied Physics Vol.20 No.10

The performance of ultra-thin Au–Ag–Au tri-layer film deposited thermally over a flexible substrate is investigated using structural, optical, mechanical and electrical-transport measurements. The optimum total thickness of the tri-layer for high transparency and conductivity is determined to be around 8 nm using a theoretical model. The Au–Ag–Au tri-layer shows maximum transmittance (≅ 62%) at wavelength 500 nm. XRD pattern shows peak corresponding to (111) plane of Au and/or Ag. Sheet resistance (≅ 10.42 Ω/□) measured at 300 K using four probe technique is stable up to 150 °C. Hall effect measurements show high conductivity (1.34 × 105 (Ω cm)−1), carrier concentration (2.48 × 1023/cm3), and mobility (3.4 cm2/Vs). Scotch tape test confirms good adhesion of the film onto PET substrate. Bending-twisting tests using an indigenous apparatus indicate high resistance-stability even after 50,000 cycles. These results imply the viability of Au–Ag–Au tri-layer film as a transparent conducting electrode worth exploring for optoelectronic applications.