Electrocatalytic performance evaluation of cobalt hydroxide and cobalt oxide thin films for oxygen evolution reaction

Babar, P.T.,Lokhande, A.C.,Pawar, B.S.,Gang, M.G.,Jo, Eunjin,Go, Changsik,Suryawanshi, M.P.,Pawar, S.M.,Kim, Jin Hyeok Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.427 No.1

<P><B>Abstract</B></P> <P>The development of an inexpensive, stable, and highly active electrocatalyst for oxygen evolution reaction (OER) is essential for the practical application of water splitting. Herein, we have synthesized an electrodeposited cobalt hydroxide on nickel foam and subsequently annealed in an air atmosphere at 400°C for 2h. In-depth characterization of all the films using X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) techniques, which reveals major changes for their structural, morphological, compositional and electrochemical properties, respectively. The cobalt hydroxide nanosheet film shows high catalytic activity with 290mV overpotential at 10mAcm<SUP>−2</SUP> and 91mVdec<SUP>−1</SUP> Tafel slope and robust stability (24h) for OER in 1M KOH electrolyte compared to cobalt oxide (340mV). The better OER activity of cobalt hydroxide in comparison to cobalt oxide originated from high active sites, enhanced surface, and charge transport capability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simple and highly efficient method for deposition of Cobalt based electrode. </LI> <LI> Efficient OER performance of Co(OH)<SUB>2</SUB>. </LI> <LI> Co(OH)<SUB>2</SUB> exhibits low overpotential (290mV) over Co<SUB>3</SUB>O<SUB>4</SUB> (340mV) at current density of 10mAcm<SUP>−2</SUP>. </LI> <LI> Superior performance of Co(OH)<SUB>2</SUB> mainly due to large surface and active sites compare to Co<SUB>3</SUB>O<SUB>4</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Thermally oxidized porous NiO as an efficient oxygen evolution reaction (OER) electrocatalyst for electrochemical water splitting application

Babar, P.T.,Lokhande, A.C.,Gang, M.G.,Pawar, B.S.,Pawar, S.M.,Kim, Jin Hyeok Elsevier 2018 Journal of industrial and engineering chemistry Vol.60 No.-

<P><B>Abstract</B></P> <P>Low-cost and competent electrocatalysts play a key role in an electrocatalytic water oxidation reaction. Herein, we report that readily available bare nickel foam (NF) can be used as conductive substrate and precursor to grow a porous nickel oxide (NiO) using a simple and scalable thermal oxidation method. The obtained NiO supported on NF is used as binder-free electrocatalyst for the oxygen evolution reaction (OER) and its electrochemical properties are evaluated by linear sweep voltammetry (LSV) in 1M KOH. The porous NiO thin film acts as an efficient electrocatalyst for the OER and achieves a catalytic current density of 10mAcm<SUP>−2</SUP> at an overpotential of 310mV with a smaller Tafel slope of 54mVdec<SUP>−1</SUP>. The electrode also shows good durability over 24h with negligible degradation. This durable and high-performance electrocatalyst can be a competitor to electrocatalysts that consist of costly elements and, require advanced synthesis; the NiO electrocatalyst shows progress towards the replacement of noble metal-based electrocatalysts for the OER.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Porous NiO has been synthesized by a simple thermal oxidation method. </LI> <LI> Thermally oxidized NiO show significantly enhanced OER activity. </LI> <LI> It is promising for fabrication of low-cost and robust OER electrode. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication of pulsed laser deposited Ge doped CZTSSe thin film based solar cells: Influence of selenization treatment

Lokhande, A.C.,Chalapathy, R.B.V.,Jang, J.S.,Babar, P.T.,Gang, M.G.,Lokhande, C.D.,Kim, Jin Hyeok North-Holland 2017 Solar Energy Materials and Solar Cells Vol. No.

<P><B>Abstract</B></P> <P>In the present work, Ge doped CZTGeS thin films are pulsed laser deposited followed by annealing treatment in selenium environment. The influence of selenization condition on the structural, morphological, optical and electrical properties of the absorber thin films are investigated. The thin films characterized using X-ray diffraction (XRD) and Raman spectroscopy techniques confirm the formation of Kesterite CZTGeSSe thin film compound with dominant A1 mode vibration. The morphological and optical studies of the thin films reveal the formation of compact and void free microstructure with optimal band gap in the range of 1–1.2eV. The impact of selenization temperature on the quality of thin films has been studied and thin film solar cells are fabricated with CZTGeSSe absorbers grown at various annealing temperatures from 525 to 575℃ to evaluate the performance of devices as a function of an annealing temperature. The elemental Ge and Sn losses from the absorber compound confirmed from X-ray fluorescence spectroscopy (XRF) depended on the annealing temperature and linearly increased with increasing temperature affecting the optical, compositional and microstructural properties of the thin films. Compositional non uniformity is one of the factors that limit the performance of solar cell device. PLD technique due to its advantage of achieving precise stoichiometry control combined with optimized selenization conditions can potentially address the issue. Compared to solar cell fabricated from absorber compound annealed at 525 and 575℃, the solar cell fabricated from the absorber annealed at 550℃ exhibited the best conversion efficiency of 3.82% with V<SUB>oc</SUB> 434mV, J<SUB>sc</SUB> 18.33mA/cm<SUP>2</SUP>, FF 47.0% and retained nearly 90% power conversion efficiency (PCE) stability after time period of 60 days.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pulsed laser deposition of Ge doped CZTS thin films. </LI> <LI> Band gap tuning of CZTGeS thin films with selenization treatment. </LI> <LI> Effect of annealing conditions on structural, optical and morphological properties of CZTGeSSe thin films. </LI> <LI> Fabrication of CZTGeSSe thin film solar cells with efficiency over 3.82%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

SILAR deposited iron phosphate as a bifunctional electrocatalyst for efficient water splitting

Babar, P.T.,Lokhande, A.C.,Shim, H.J.,Gang, M.G.,Pawar, B.S.,Pawar, S.M.,Kim, Jin Hyeok Elsevier 2019 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.534 No.-

<P><B>Abstract</B></P> <P>The development of efficient and earth-abundant electrocatalysts for overall water splitting is important but still challenging. Herein, iron phosphate (FeP<I>i</I>) electrode is synthesized using a successive ionic layer deposition and reaction (SILAR) method on a nickel foam substrate at room temperature and is used as a bifunctional electrocatalyst for water splitting. The prepared FeP<I>i</I> electrodes show excellent electrocatalytic activity and stability for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The FeP<I>i</I> electrode exhibits low overpotential of 230 mV and 157 mV towards the OER and HER, respectively, with superior long-term stability. As a result, an electrolyzer that exploits FeP<I>i</I> as both the anode and the cathode is constructed, which requires a cell potential of 1.67 V to deliver a 10 mA cm<SUP>−2</SUP> current density in 1 M KOH solution. The exceptional features of the catalyst lie in its structure and active metal sites, increasing surface area, accelerated electron transport and promoted reaction kinetics. This study may provide a facile and scalable approach to design a high-efficiency, earth-abundant electrocatalyst for water splitting.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Binder-free novel Cu₄SnS₄ electrode for high-performance supercapacitors

Lokhande, A.C.,Patil, Amar,Shelke, A.,Babar, P.T.,Gang, M.G.,Lokhande, V.C.,Dhawale, Dattatray S.,Lokhande, C.D.,Kim, Jin Hyeok Elsevier 2018 ELECTROCHIMICA ACTA Vol.284 No.-

<P><B>Abstract</B></P> <P>In this work, for the first time, we report the direct coating of ternary chalcogenide-based nanostructured Cu<SUB>4</SUB>SnS<SUB>4</SUB> (CTS) thin film electrodes for the energy storage application. The phase purity, composition, microstructure, optical and electrical properties of the synthesized electrode are validated through comprehensive characterization techniques. In the supercapacitive application, the CTS electrode delivers an excellent performance with the maximum specific capacitance of 704 F/g, an energy density of 27.77 Wh/kg and a power density of 7.14 kW/kg in 1 M NaOH electrolyte solution. The intrinsic electrode properties such as the electronic conductivity, crystal structure and film hydrophilicity are found to be influential parameters for the obtained high performance and are studied in detail. Furthermore, the solid-state supercapacitive device fabricated using CTS electrodes and polymer gel electrolyte (PVA/NaOH) in a symmetric configuration, demonstrated the highest specific capacitance of 34.9 F/g with an energy density of 2.4 Wh/kg, a power density of 0.291 kW/kg and more than 89.9% capacitive retention. The presented work reports a simple, cost-effective, scalable and replicable approach for electrode application in supercapacitor industry.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Specific capacitance of 704 F/g, an energy density of 27.77 Wh/kg and a power density of 7.14 kW/kg. </LI> <LI> The intrinsic electrode properties, such as the electronic conductivity, crystal structure and hydrophilicity are found to be influential parameters. </LI> <LI> Symmetric device: specific capacitance of 34.9 F/g, an energy density of 2.4 Wh/kg, a power density of 0.291 kW/kg with 89.9% capacitive retention for 1000 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The obtained porous microstructure of the CTS thin film electrode using SILAR method and its electrochemical characterization in solid-state symmetric configuration. The CV and GCD curves are accomplished in the potential window range of 0–1.2 V. The device exhibited 89.9% stability retention after 1000 CV cycles.</P> <P>[DISPLAY OMISSION]</P>

Annealing temperature dependent catalytic water oxidation activity of iron oxyhydroxide thin films

Babar, P.T.,Pawar, B.S.,Lokhande, A.C.,Gang, M.G.,Jang, J.S.,Suryawanshi, M.P.,Pawar, S.M.,Kim, Jin Hyeok Elsevier 2017 Journal of energy chemistry Vol.26 No.4

<P>Nanostructured iron oxyhydroxide (FeOOH) thin films have been synthesized using an electrodeposition method on a nickel foam (NF) substrate and effect of air annealing temperature on the catalytic performance is studied. The as-deposited and annealed thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and linear sweep voltammetry (LSV) to determine their structural, morphological, compositional and electrochemical properties, respectively. The as-deposited nanostructured amorphous FeOOH thin film is converted into a polycrystalline Fe2O3 with hematite crystal structure at a high temperature. The FeOOH thin film acts as an efficient electrocatalyst for the oxygen evolution reaction (OER) in an alkaline 1 M KOH electrolyte. The film annealed at 200 degrees C shows high catalytic activity with an onset overpotential of 240 mV with a smaller Tafel slope of 48 mV/dec. Additionally, it needs an overpotential of 290 mV to the drive the current density of 10 mA/cm(2) and shows good stability in the 1 M KOH electrolyte solution. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.</P>

Facile electrosynthesis of Fe (Ni/Co) hydroxyphosphate as a bifunctional electrocatalyst for efficient water splitting

P.T. Babar,A.C. Lokhande,조은애,B.S. Pawar,M.G. Gang,S.M. Pawar,J.H. Kim 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.70 No.-

Porous iron–nickel hydroxyphosphate and iron–cobalt hydroxyphosphate electrodes are prepared byone-step electrodeposition method. The as-prepared iron–nickel hydroxyphosphate and iron–cobalthydroxyphosphate electrodes show excellent performance for water splitting with high catalytic activitytowards the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), with a loweroverpotential of 220 and 235 mV for the OER and 145 and 160 mV for the HER, respectively. Moreover,two-electrode electrolyzer using iron-nickel hydroxyphosphate as both the anode and cathode requires acell voltage of 1.65 V while iron–cobalt hydroxyphosphate requires cell voltage of 1.67 V to gain currentdensity of 10 mA cm 2.

Thermally oxidized porous NiO as an efficient oxygen evolution reaction (OER) electrocatalyst for electrochemical water splitting application

P.T. Babar,A.C. Lokhande,M.G. Gang,B.S. Pawar,S.M. Pawar,김진혁 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.60 No.-

Low-cost and competent electrocatalysts play a key role in an electrocatalytic water oxidation reaction. Herein, we report that readily available bare nickel foam (NF) can be used as conductive substrate and precursor to grow a porous nickel oxide (NiO) using a simple and scalable thermal oxidation method. The obtained NiO supported on NF is used as binder-free electrocatalyst for the oxygen evolution reaction (OER) and its electrochemical properties are evaluated by linear sweep voltammetry (LSV) in 1 M KOH. The porous NiO thin film acts as an efficient electrocatalyst for the OER and achieves a catalytic current density of 10 mA cm−2 at an overpotential of 310 mV with a smaller Tafel slope of 54 mV dec−1. The electrode also shows good durability over 24 h with negligible degradation. This durable and high-performance electrocatalyst can be a competitor to electrocatalysts that consist of costly elements and, require advanced synthesis; the NiO electrocatalyst shows progress towards the replacement of noble metal-based electrocatalysts for the OER.

CoFe hydroxide as highly efficient electrocatalyst for oxygen evolution reaction

P. T. Babar,Jinhyeok Kim(김진혁) 한국신재생에너지학회 2017 한국신재생에너지학회 학술대회논문집 Vol.2017 No.5

Electrodeposited Cobalt oxide as highly efficient electrocatalyst for oxygen evolution reaction

P.T.Babar,Jin Hyeok Kim 한국신재생에너지학회 2017 한국신재생에너지학회 학술대회논문집 Vol.2017 No.9