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Solution Processed Porous Fe<sub>2</sub>O<sub>3</sub> Thin Films for Solar-Driven Water Splitting
Suryawanshi, Mahesh P.,Kim, Seonghyeop,Ghorpade, Uma V.,Suryawanshi, Umesh P.,Jang, Jun Sung,Gang, Myeng Gil,Kim, Jin Hyeok,Moon, Jong Ha Materials Research Society of Korea 2017 한국재료학회지 Vol.27 No.11
We report facile solution processing of mesoporous hematite (${\alpha}-Fe_2O_3$) thin films for high efficiency solar-driven water splitting. $Fe_2O_3$ thin films were prepared on fluorine doped tin oxide(FTO) conducting substrates by spin coating of a precursor solution followed by annealing at $550^{\circ}C$ for 30 min. in air ambient. Specifically, the precursor solution was prepared by dissolving non-toxic $FeCl_3$ as an Fe source in highly versatile dimethyl sulfoxide(DMSO) as a solvent. The as-deposited and annealed thin films were characterized for their morphological, structural and optical properties using field-emission scanning electron microscopy(FE-SEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and UV-Vis absorption spectroscopy. The photoelectrochemical performance of the precursor (${\alpha}-FeOOH$) and annealed (${\alpha}-Fe_2O_3$) films were characterized and it was found that the ${\alpha}-Fe_2O_3$ film exhibited an increased photocurrent density of ${\sim}0.78mA/cm^2$ at 1.23 V vs. RHE, which is about 3.4 times higher than that of the ${\alpha}-FeOOH$ films ($0.23mA/cm^2$ at 1.23 V vs. RHE). The improved performance can be attributed to the improved crystallinity and porosity of ${\alpha}-Fe_2O_3$ thin films after annealing treatment at higher temperatures. Detailed electrical characterization was further carried out to elucidate the enhanced PEC performance of ${\alpha}-Fe_2O_3$ thin films.
Suryawanshi, M.P.,Shin, S.W.,Ghorpade, U.V.,Gurav, K.V.,Agawane, G.L.,Hong, C.W.,Yun, J.H.,Patil, P.S.,Kim, J.H.,Moholkar, A.V. Association for Applied Solar Energy ; Elsevier Sc 2014 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.110 No.-
A cost-effective chemical approach is developed for the synthesis of photoelectrochemically active Cu<SUB>2</SUB>ZnSnS<SUB>4</SUB> (CZTS) thin films. More specifically, CZTS precursor thin films are prepared by the sequential deposition of Cu<SUB>2</SUB>SnS<SUB>3</SUB> and ZnS layers using a successive ionic adsorption and reaction (SILAR) technique. The CZTS precursor thin films are sulfurized at different temperatures ranging from 500 to 575<SUP>o</SUP>C at intervals of 25<SUP>o</SUP>C. The influence of different sulfurization temperatures on the structural, compositional, morphological, and optical properties, as well as on the photoelectrochemical performance is studied. The films sulfurized at 575<SUP>o</SUP>C showed a prominent kesterite phase with a nearly stoichiometric composition, dense microstructure with the desired thickness, and an optical band gap energy of 1.47eV. The photoelectrochemical (PEC) cell fabricated using CZTS thin film sulfurized at 575<SUP>o</SUP>C showed the highest short circuit current density (J<SUB>sc</SUB>) of 8.27mA/cm<SUP>2</SUP> with a power conversion efficiency (η) of 1.06%.
Suryawanshi, M.,Shin, S.,Ghorpade, U.,Song, D.,Hong, C.,Han, S. S.,Heo, J.,Kang, S.,Kim, J. Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.9
<P>The development of solution-processable routes as well as compounds consisting of earth abundant elements is highly desirable to reduce the fabrication cost. Recently, kesterite Cu2ZnSnS4 (CZTS) nanocrystals (NCs) have attracted great attention for photoelectrochemical (PEC) water splitting owing to their suitable low-cost, earth-abundancy and suitable band gap energy. However, the environmentally benign synthesis of high-quality CZTS NCs without toxic solvents remains elusive. Here, a green chemistry approach employing vegetable oil as a non-toxic solvent for the synthesis of monodisperse and size-tunable CZTS NCs is introduced for the first time. Additionally, the relationship between the abnormal size behavior of the CZTS NCs and the degree of decomposition in the vegetable oil using electrospray ionization mass spectrometry (ESI-MS) measurements is elucidated for the first time. As a conceptual strategy, a ternary abundant compound based heterojunction nanostructure for efficient solar water splitting by introducing CZTS NCs onto 5 nm Zn(O,S) passivated layer/hydrothermally grown TiO2 nanorod arrays (TNRs) is designed and developed. Remarkably, this ternary CZTS NCs/Zn(O,S)/TNR photoelectrode shows a photocurrent density as high as 15.05 mA cm(-2) at 1.23 V (vs. the NHE), which is the highest ever for previously reported CZTS NC-based photoelectrodes. The reasons for the enhanced PEC performance are discussed in detail based on different PEC characterizations. More importantly, this work reflects the sophistication of eco-friendly solution phase synthesized CZTS NCs without using any toxic chemicals as an earth abundant sensitizer and constitute a new paradigm towards the enhanced PEC performance with quantum dot based hetero-nanostructures.</P>
Suryawanshi Hiralal M.,Borghate Vijay B.,Ramteke Manojkumar R.,Thakre Krishna L. The Korean Institute of Power Electronics 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.4
This paper deals with novel electronic ballast based on single-stage power processing topology using a symmetrical half-bridge inverter and current injection circuit. The half-bridge inverter drives the output parallel resonant circuit and injects current through the power factor correction (PFC) circuit. Because of high frequency current injection and high frequency modulated voltage, the proposed circuit maintains the unity power factor (UPF) with low THD even under wide variation in ac input voltage. This circuit needs minimum and lower sized components to achieve the UPF and high efficiency. This leads to an increase in reliability of ballast at low cost. Furthermore, to reduce cost, the electronic ballast is designed for two series-connected fluorescent lamps (FL). The analysis and experimental results are presented for ($2{\times}36$ Watt) fluorescent lamps operating at 50 kHz switching frequency and input line voltage (230 V, 50 Hz).
Suryawanshi, Mahesh P.,Ghorpade, Uma V.,Shin, Seung Wook,Pawar, Sachin A.,Kim, In Young,Hong, Chang Woo,Wu, Minhao,Patil, Pramod S.,Moholkar, Annasaheb V.,Kim, Jin Hyeok American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.18
<P>A simple and eco-friendly method of solution processing of Cu2SnS3 (CTS) absorbers using an aqueous precursor solution is presented. The precursor solution was prepared by mixing metal salts into a mixture of water and ethanol (5:1) with monoethanolamine as an additive at room temperature. Nearly carbon-free CTS films were formed by multispin coating the precursor solution and heat treating in air followed by rapid thermal annealing in S vapor atmosphere at various temperatures. Exploring the role of the annealing temperature in the phase, composition, and morphological evolution is essential for obtaining highly efficient CTS-based thin film solar cells (TFSCs). Investigations of CTS absorber layers annealed at various temperatures revealed that the annealing temperature plays an important role in further improving device properties and efficiency. A substantial improvement in device efficiency occurred only at the critical annealing temperature, which produces a compact and void-free microstructure with large grains and high crystallinity as a pure-phase absorber layer. Finally, at an annealing temperature of 600 degrees C, the CTS thin film exhibited structural, compositional, and microstructural isotropy by yielding a reproducible power conversion efficiency of 1.80%. Interestingly, CTS TFSCs exhibited good stability when stored in an air atmosphere without encapsulation at room temperature for 3 months, whereas the performance degraded slightly when subjected to accelerated aging at 80 degrees C for 100 h under normal laboratory conditions.</P>
Suryawanshi, Mahesh P.,Shin, Seung Wook,Ghorpade, Uma V.,Kim, Jihun,Jeong, Hye Won,Kang, Soon Hyung,Kim, Jin Hyeok The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.42
<P>A low-cost, highly efficient and durable photoelectrochemical (PEC) water-splitting system can be realized through designing a hierarchical core/shell nanostructured photoanode entirely composed of Earth-abundant elements. Herein, we report the rational design of a core/shell nanostructured photoanode with a TiO2 nanorod (NR) array as the core and a highly active Earth-abundant NiFe oxyhydroxide ((Ni1−xFex)OOH, NiFeOOH) oxygen evolution catalyst (OEC) as the shell for PEC water oxidation. Specifically, the NiFeOOH nanosheets were prepared <I>via</I> a facile, one-step electroless deposition method for a short reaction time of 10 min at room temperature. The TiO2/NiFeOOH core/shell nanostructured photoanode exhibits an unprecedented enhancement in photocurrent density (3.85 mA cm<SUP>−2</SUP> at 1.23 V <I>vs.</I> a reversible hydrogen electrode, (RHE)), no decay in photocurrent density over 24 h, and an obvious cathodic onset potential shift of 133 mV compared to the TiO2 NRs (0.73 mA cm<SUP>−2</SUP> at 1.23 V <I>vs.</I> RHE). The electron transfer mechanism is discussed through electrochemical impedance spectroscopy studies and calculated band alignments <I>via</I> ultraviolet photoelectron spectroscopy characterization. This work not only suggests a simple, room temperature electroless strategy for integrating Earth-abundant catalysts with photoanodes, but also accelerates the development of rationally designed core/shell photoanodes for efficient and durable solar water oxidation.</P>
Hiralal M. Suryawanshi,Vijay B. Borghate,Manojkumar R. Ramteke,Krishna L. Thakre 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.4
This paper deals with novel electronic ballast based on single-stage power processing topology using a symmetrical half-bridge inverter and current injection circuit. The half-bridge inverter drives the output parallel resonant circuit and injects current through the power factor correction (PFC) circuit. Because of high frequency current injection and high frequency modulated voltage, the proposed circuit maintains the unity power factor (UPF) with low THD even under wide variation in ac input voltage. This circuit needs minimum and lower sized components to achieve the UPF and high efficiency. This leads to an increase in reliability of ballast at low cost. Furthermore, to reduce cost, the electronic ballast is designed for two series-connected fluorescent lamps (FL). The analysis and experimental results are presented for (2 × 36 Watt) fluorescent lamps operating at 50 ㎑ switching frequency and input line voltage (230 V, 50 ㎐).