Electrosynthesis of copper phosphide thin films for efficient water oxidation

Pawar, Sambhaji M.,Pawar, Bharati S.,Babar, Pravin T.,Aqueel Ahmed, Abu Talha,Chavan, Harish S.,Jo, Yongcheol,Cho, Sangeun,Kim, Jongmin,Inamdar, Akbar I.,Kim, Jin Hyeok,Kim, Hyungsang,Im, Hyunsik Elsevier 2019 Materials letters Vol.241 No.-

<P><B>Abstract</B></P> <P>A copper phosphide (Cu<SUB>3</SUB>P) thin film is synthesized on a Ni foam using a one-step electrodeposition method at room temperature and annealed at 300 °C in Ar atmosphere. The Cu<SUB>3</SUB>P film is amorphous and has a flat morphology with surface voids. It works as an electrocatalyst for water oxidation in an alkaline 1 M KOH electrolyte. It exhibits excellent catalytic oxygen evolution reaction with an overpotential of 310 mV, Tafel slope of 88 mV/dec, and good stability over 20 h of operation at 10 mA/cm<SUP>2</SUP>. The excellent OER performance is due to its large electrochemically active surface area and low charge transfer resistance at the catalyst-electrolyte interface after the annealing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Amorphous copper phosphide OER catalyst is synthesized by one-step electrodeposition. </LI> <LI> A smooth morphology with surface void is obtained after annealing. </LI> <LI> An overpotential of 310 mV at 10 mA/cm<SUP>2</SUP> with a Tafel slope of 88 mV/dec is demonstrated. </LI> <LI> Excellent long-term electrochemical durability is observed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nanoporous CuCo₂O₄ nanosheets as a highly efficient bifunctional electrode for supercapacitors and water oxidation catalysis

Pawar, Sambhaji M.,Pawar, Bharati S.,Babar, Pravin T.,Ahmed, Abu Talha Aqueel,Chavan, Harish S.,Jo, Yongcheol,Cho, Sangeun,Kim, Jongmin,Hou, Bo,Inamdar, Akbar I.,Cha, SeungNam,Kim, Jin Hyeok,Kim, Tae Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.470 No.-

<P><B>Abstract</B></P> <P>Efficient and low‐cost multifunctional electrodes play a key role in improving the performance of energy conversion and storage devices. In this study, ultrathin nanoporous CuCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets are synthesized on a nickel foam substrate using electrodeposition followed by air annealing. The CuCo<SUB>2</SUB>O<SUB>4</SUB> nanosheet electrode exhibits a high specific capacitance of 1473 F g<SUP>─1</SUP> at 1 A g<SUP>─1</SUP> with a capacity retention of ∼93% after 5000 cycles in 3 M KOH solution. It also works well as an efficient oxygen evolution reaction electrocatalyst, demonstrating an overpotential of 260 mV at 20 mA cm<SUP>─2</SUP> with a Tafel slope of ∼64 mV dec<SUP>─1</SUP>. in 1 M KOH solution, which is the lowest reported among other copper-cobalt based transition metal oxide catalysts. The catalyst is very stable at >20 mA cm<SUP>─2</SUP> for more than 25 h. The superior electrochemical performance of the CuCo<SUB>2</SUB>O<SUB>4</SUB> nanosheet electrode is due to the synergetic effect of the direct growth of 2D nanosheet structure and a large electrochemically active surface area associated with nanopores on the CuCo<SUB>2</SUB>O<SUB>4</SUB> nanosheet surface.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultrathin nanoporous CuCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets electrode synthesized by electrodeposition. </LI> <LI> High specific capacitance and good cycling stability were obtained. </LI> <LI> Highly efficient OER electrocatalyst with an overpotential of 260 mV at 20 mA/cm<SUP>2</SUP>. </LI> <LI> Excellent long-term electrochemical durability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication of Cu₂ZnSn(S_<i>x</i>Se_<i>1−x</i>)₄ thin film solar cell by single step sulfo-selenization of stacked metallic precursors

Pawar, Sambhaji M.,Inamdar, Akbar I.,Gurav, Kishor V.,Shin, Seung Wook,Gwak, Jihye,Jo, Yongcheol,Yun, JaeHo,Pak, Hisun,Kwon, Sehan,Kim, Hyungsang,Kim, Jin Hyeok,Im, Hyunsik Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.2

<P>We have synthesized an efficient Cu2ZnSn(SxSe1-x)(4) (CZTSSe) absorbers by using single-step rapid thermal sulfo-selenization process of sputtered stack metallic precursor (Zn/Sn/Cu) films. The structural and morphological studies confirm that the suitability of the rapid thermal sulfo-selenization process for the synthesis of a CZTSSe absorber without any secondary phases with large grains. The annealing atmosphere with a mixed-chalcogen source enhances the grain growth of the CZTSSe absorber as compared with pure Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) absorbers. The CZTSSe thin film solar cell shows the best conversion efficiency of similar to 7%. (C) 2014 Elsevier B. V. All rights reserved.</P>

Self-assembled two-dimensional copper oxide nanosheet bundles as an efficient oxygen evolution reaction (OER) electrocatalyst for water splitting applications

Pawar, Sambhaji M.,Pawar, Bharati S.,Hou, Bo,Kim, Jongmin,Aqueel Ahmed, Abu Talha,Chavan, Harish. S.,Jo, Yongcheol,Cho, Sangeun,Inamdar, Akbar I.,Gunjakar, Jayavant L.,Kim, Hyungsang,Cha, SeungNam,Im, The Royal Society of Chemistry 2017 Journal of materials chemistry. A, Materials for e Vol.5 No.25

<P>A high activity of a two-dimensional (2D) copper oxide (CuO) electrocatalyst for the oxygen evolution reaction (OER) is presented. The CuO electrode self-assembles on a stainless steel substrate<I>via</I>chemical bath deposition at 80 °C in a mixed solution of CuSO4and NH4OH, followed by air annealing treatment, and shows a 2D nanosheet bundle-type morphology. The OER performance is studied in a 1 M KOH solution. The OER starts to occur at about 1.48 V<I>versus</I>the RHE (<I>η</I>= 250 mV) with a Tafel slope of 59 mV dec<SUP>−1</SUP>in a 1 M KOH solution. The overpotential (<I>η</I>) of 350 mV at 10 mA cm<SUP>−2</SUP>is among the lowest compared with other copper-based materials. The catalyst can deliver a stable current density of >10 mA cm<SUP>−2</SUP>for more than 10 hours. This superior OER activity is due to its adequately exposed OER-favorable 2D morphology and the optimized electronic properties resulting from the thermal treatment.</P>

Optimizing nanosheet nickel cobalt oxide as an anode material for bifunctional electrochemical energy storage and oxygen electrocatalysis

Cho, Sangeun,Lee, Seongwoo,Hou, Bo,Kim, Jongmin,Jo, Yongcheol,Woo, Hyeonseok,Pawar, Sambhaji M.,Inamdar, Akbar I.,Park, Youngsin,Cha, SeungNam,Kim, Hyungsang,Im, Hyunsik Pergamon Press 2018 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>Mesoporous Ni-Co oxide (NCO) nanosheet electrodes are fabricated on Ni foam via an electrodeposition technique. Their bifunctional activities for electrochemical energy storage and electro-catalysis for water splitting in strong alkaline media are optimized by varying the ratio of concentrations of the Ni and Co precursors. The ratio-based changes vary the pore size of the NCO nanosheets between 92.5 and 200 nm, and structural analyses reveal that the electrode films have a spinel NiCo<SUB>2</SUB>O<SUB>4</SUB> structure. The obtained specific capacitance varies dramatically between 613 and 2704 Fg<SUP>−1</SUP> at 2 mA cm<SUP>−2</SUP>, with good capacity retention (80–90%) after 2000 cycles. The NCO nanosheet electrodes also exhibit a good oxygen evolution reaction at the surface. The lowest overpotential (315 mV at 10 mA cm<SUP>−2</SUP>) is obtained with a Tafel slope of 59 mV dec<SUP>−1</SUP>. The observed bifunctional activities of the new NCO nanosheet electrode are superior to those of nanostructured NCO electrodes prepared via hydrothermal and SILAR methods. The analyses regarding the electrochemically active surface area and electrochemical impedance spectroscopy, together with the observed electrochemical performance, reveal that the most-optimized Ni and Co composition produces the synergetic effects of an electrochemically active surface area and great stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mesoporous Ni-Co oxide (NCO) nanosheet electrodes are fabricated on Ni foam via an electrodeposition technique. </LI> <LI> Excellent specific capacitance and electrochemical stability are obtained. </LI> <LI> The overpotential of 315 mV at 10 mA cm<SUP>−2</SUP> is obtained with a Tafel slope of 59 mV dec<SUP>−1</SUP>. </LI> </UL> </P>

Highly efficient electro-optically tunable smart-supercapacitors using an oxygen-excess nanograin tungsten oxide thin film

Inamdar, Akbar I.,Kim, Jongmin,Jo, Yongcheol,Woo, Hyeonseok,Cho, Sangeun,Pawar, Sambhaji M.,Lee, Seongwoo,Gunjakar, Jayavant L.,Cho, Yuljae,Hou, Bo,Cha, SeungNam,Kwak, Jungwon,Park, Youngsin,Kim, Hyun North-Holland 2017 Solar Energy Materials and Solar Cells Vol. No.

<P><B>Abstract</B></P> <P>A smart supercapacitor shares the same electrochemical processes as a conventional energy storage device while also having electrochromic functionality. The smart supercapacitor device can sense the energy storage level, which it displays in a visually discernible manner, providing increased convenience in everyday applications. Here, we report an electro-optically tunable smart supercapacitor based on an oxygen-rich nanograin WO<SUB>3</SUB> electrode. The nanostructured WO<SUB>3</SUB> electrode is dark blue in color in the charged state and becomes transparent in its discharged state with a high optical modulation of 82%. The supercapacitor has a specific capacitance of 228Fg<SUP>−1</SUP> at 0.25 Ag<SUP>−1</SUP> with a large potential window (1.4V). It is highly durable, exhibits good electrochemical stability over 2000 cycles, retains 75% of its initial capacitance, and exhibits high coloration efficiency (~170cm<SUP>2</SUP>/C). The excellent electrochromic and electrochemical supercapacitor properties of the electrode is due to the synergetic effect between nanograin morphology and excess oxygen. A smart-supercapacitor fabricated with an oxygen-rich nanograin WO<SUB>3</SUB> electrode exhibits a superb combination of energy storage and highly-efficient electrochromic features in one device that can monitor the energy storage level through visible changes in color.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oxygen-excess nanograin WO<SUB>3+δ</SUB> is synthesized for a smart supercapacitor electrode. </LI> <LI> It is dark blue in the charged state and transparent in the discharged state with an optical modulation of 82%. </LI> <LI> The device exhibits an excellent coloration efficiency of ~170cm<SUP>2</SUP>/C. </LI> <LI> The specific capacity is 228Fg<SUP>−1</SUP> with a large potential window of 1.4V. </LI> </UL> </P>

Ultrathin Ni-Mo oxide nanoflakes for high-performance supercapacitor electrodes

Chavan, Harish S.,Hou, Bo,Ahmed, Abu Talha Aqueel,Kim, Jongmin,Jo, Yongcheol,Cho, Sangeun,Park, Youngsin,Pawar, Sambhaji M.,Inamdar, Akbar I.,Cha, Seung Nam,Kim, Hyungsang,Im, Hyunsik Elsevier 2018 Journal of Alloys and Compounds Vol.767 No.-

<P><B>Abstract</B></P> <P>Supercapacitors based on nanomaterial electrodes exhibit great potential as power sources for advanced electronic devices. From a practical viewpoint, it is desirable to fabricate highly active and sustainable nanomaterial electrodes consisting of non-precious elements using a simple technique in a controllable way. In this work, we report the synthesis of a self-assembled ultra-thin porous nanoflake Ni-Mo oxide (NMO) film using the successive ionic layer adsorption and reaction (SILAR) technique. The nanoflake NMO thin film electrode with a large electrochemically active surface area of ∼108 cm<SUP>−2</SUP> exhibits a high specific capacitance of 1180 Fg<SUP>−1</SUP> at a current density of 1 Ag<SUP>−1</SUP> and excellent rate capability, with a negligible capacity loss of 0.075% per cycle. Even at a high current rate of 10 A g<SUP>−1</SUP> it retains a capacity of 600 Fg<SUP>−1</SUP>. The highest energy and power densities obtained are 119 Whkg<SUP>−1</SUP> and 15.7 kWkg<SUP>−1</SUP>, respectively. Electrochemical impedance spectroscopy analyses reveal that the electrode has considerably low charge transfer resistance. The observed excellent electrochemical energy storage performance of the nanoflake NMO electrode with a nanoporous surface is due to the synergetic effects of the large electrochemically active surface area, enhanced ion diffusion, and improved electrical conductivity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultra-thin porous Ni-Mo oxide nanoflakes self-assemble on stainless steel via a SILAR method. </LI> <LI> Large electrochemically-active surface area, enhanced ion diffusion and robust adhesion result in superior performance. </LI> <LI> High specific capacitance of 1180 F/g and energy density of 119 Wh/kg at 1 A/g are achieved. </LI> </UL> </P>

Nanograin tungsten oxide with excess oxygen as a highly reversible anode material for high-performance Li-ion batteries

Inamdar, Akbar I.,Chavan, Harish.S.,Ahmed, Abu Talha Aqueel,Cho, Sangeun,Kim, Jongmin,Jo, Yongcheol,Pawar, Sambhaji M.,Park, Youngsin,Kim, Hyungsang,Im, Hyunsik North-Holland 2018 Materials Letters Vol. No.

<P><B>Abstract</B></P> <P>Nanogranular tungsten oxide (WO<SUB>3</SUB>) with excess oxygen is synthesized and its battery performance is evaluated as an anode material for the Li-ion battery (LIB). The formation of a monoclinic WO<SUB>3</SUB> phase is confirmed using X-ray diffraction (XRD) and micro (µ)-Raman spectroscopy analyses. The Rutherford back scattering results confirm the existence of excess oxygen in the film. The charge discharge processes are associated with the conversion of the WO<SUB>3</SUB> from the oxide state to the metallic state, and vice versa, and it shows a maximum specific capacity of 778.8 mAh g<SUP>−1</SUP> at a current density of 0.1 Ag<SUP>−1</SUP> in the first discharge. Even at a very high current density of 1 Ag<SUP>−1</SUP>, the sample retains the capacity of 228.6 mAh g<SUP>−1</SUP>. It shows excellent rate capability and a long-term cycling stability over 500 charge–discharge cycles, with capacity retention of 217%. The observed high discharge capacity and superior long-term cyclability of the nanograin WO<SUB>3</SUB> anode are attributable to the synergetic effect of the excess-oxygen induced increased donor density and enhanced electrical conductivity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanogranular WO<SUB>3</SUB> with excess oxygen is synthesized as an anode material for LIB. </LI> <LI> A maximum specific capacity of ∼779 mAh g<SUP>−1</SUP> and excellent rate capability are observed. </LI> <LI> Long-term cycling stability over 500 charge–discharge cycles with high capacity retention of 217% is obtained. </LI> <LI> Capacity retention of ∼229 mAh g<SUP>−1</SUP> at a very high current density of 1 Ag<SUP>−1</SUP> is achieved. </LI> </UL> </P>

Nanoflake NiMoO₄ based smart supercapacitor for intelligent power balance monitoring

Chavan, Harish S.,Hou, Bo,Ahmed, Abu Talha Aqueel,Jo, Yongcheol,Cho, Sangeun,Kim, Jongmin,Pawar, Sambhaji M.,Cha, SeungNam,Inamdar, Akbar I.,Im, Hyunsik,Kim, Hyungsang North-Holland 2018 Solar energy materials and solar cells Vol.185 No.-

<P><B>Abstract</B></P> <P>A supercapacitor is well recognized as one of emerging energy sources for powering electronic devices in our daily life. Although various kind of supercapacitors have been designed and demonstrated, their market aspect could become advanced if the utilisation of other physicochemical properties (e.g. optical) is incorporated in the electrode. Herein, we present an electrochromic supercapacitor (smart supercapacitor) based on a nanoflake NiMoO<SUB>4</SUB> thin film which is fabricated using a facile and well-controlled successive ionic layer adsorption and reaction (SILAR) technique. The polycrystalline nanoflake NiMoO<SUB>4</SUB> electrode exhibits a large electrochemically active surface area of ~ 96.3 cm<SUP>2</SUP>. Its nanoporous architecture provides an easy pathway for the intercalation and de-intercalation of ions. The nanoflake NiMoO<SUB>4</SUB> electrode is dark-brown in the charged state and becomes transparent in the discharged state with a high optical modulation of 57%. The electrode shows a high specific capacity of 1853 Fg<SUP>–1</SUP> at a current rate of 1 Ag<SUP>–1</SUP> with a good coloration efficiency of 31.44 cm<SUP>2</SUP>/C. Dynamic visual information is obtained when the electrode is charged at different potentials, reflecting the level of energy storage in the device. The device retains 65% capacity after 2500 charge-discharge cycles compared with its initial capacity. The excellent performance of the nanoflake NiMoO<SUB>4</SUB> based smart supercapacitor is associated with the synergetic effect of nanoporous morphology with a large electrochemically active surface area and desired chemical composition for redox reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A smart device with the combined advantages of energy storage and electrochromism is presented. </LI> <LI> It is dark-brown in the charged state and transparent in the discharged state. </LI> <LI> It exhibits a coloration efficiency of ~31.44 cm<SUP>2</SUP>/C and optical modulation of 57% at 630 nm. </LI> <LI> It shows specific capacity of 1853 F/g, with 65% capacity retention after 2500 cycles. </LI> </UL> </P>

Influence of operating temperature on Li₂ZnTi₃O₈ anode performance and high-rate charging activity of Li-ion battery

Inamdar, Akbar I.,Ahmed, Abu Talha Aqueel,Chavan, Harish S.,Jo, Yongcheol,Cho, Sangeun,Kim, Jongmin,Pawar, Sambhaji M.,Hou, Bo,Cha, SeungNam,Kim, Hyungsang,Im, Hyunsik Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.15

<P><B>Abstract</B></P> <P>The temperature-dependent performance of a Li<SUB>2</SUB>ZnTi<SUB>3</SUB>O<SUB>8</SUB> (LZTO) anode and the ultrafast-charging activity of a Li-ion battery were investigated. The LZTO anode operates at different temperatures between − 5 and 55 °C and in this work its sustainability is discussed in terms of storage performance. It delivered a discharge capacity of 181.3 mA h g<SUP>−1</SUP> at 25 °C, which increased to 227.3 mA h g<SUP>−1</SUP> at 40 °C and 131.2 mA h g<SUP>−1</SUP> at − 5 °C. The variation in the discharge capacity with temperature is associated with the reaction kinetics and the change in internal resistance. It showed a capacity retention of 64% and a coulombic efficiency of 98% over 500 cycles. Exhibiting a discharge capacity of 107 mA h g<SUP>−1</SUP>, the LZTO anode was sustainable over 100 charge-discharge cycles at an ultra-high charging rate of 10 Ag<SUP>−1</SUP>. The reaction kinetics estimated from a cyclic voltammetry analysis at high scan rates revealed a capacitive-type storage mechanism.</P> <P><B>Graphical abstract</B></P> <P>We developed an ultrafast rechargeable Li<SUB>2</SUB>ZnTi<SUB>3</SUB>O<SUB>8</SUB> (LZTO) anode for lithium-ion batteries. A half-cell LZTO battery delivered the highest reversible first discharge capacity of 181.3 mA h g<SUP>−1</SUP> at a current rate of 0.1 Ag<SUP>−1</SUP> and the maximum capacity of 106.97 mA h g<SUP>−1</SUP> was obtained when charged at an ultrafast charging rate of 10.0 Ag<SUP>−1</SUP>. The LZTO showed an excellent capacity-retention of 106.28%, suggesting excellent electrode sustainability, even at ultra-high-charging rates.</P> <P>[DISPLAY OMISSION]</P>