bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective Copper Electrodeposition to a 3D Copper Nanostructure
Authors: Kobayashi Yuma , Arai Susumu 
Published: February 2020

Introduction
Three-dimensional (3D) copper nanostructures are expected to be applied as current collectors for lithium ion battery anodes due to their high electrical conductivity and large specific surface area. The production of 3D copper nanostructures usually requires complicated fabrication steps; however, we have developed a simple method for the production of 3D copper nanostructures.1) There is a disadvantage with this method in that the 3D copper nanostructure is likely to collapse due to low mechanical strength. Reinforcement of the 3D structures is thus considered to be one of the most effective methods to address this problem. This study aims to develop a reinforcement technology using a plating method that is applied after fabrication of the 3D copper nanostructures. The reinforcement technology employed here was viafilling plating technology. This technology is also expected to improve the adhesion to the substrate by selectively depositing copper to the bottom of the 3D nanostructure.
Experimental
A 3D copper nanostructure plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + 3×10-4 M polyacrylic acid) and a selective copper plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + additives) were prepared. A copper sulfate bath that does not contain additives was also employed for comparison. Pure copper and phosphorus-containing copper plates were used as the cathode and anode, respectively. Electrodeposition was conducted under galvanostatic conditions (1 A dm-2) without agitation at 25 °C. In addition, the influence of agitation on selective copper deposition was also investigated. Air agitation, magnetic stirring and a cathode rocker were used. The phase structure and microstructure of the deposits were analyzed using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively.
Results and discussion
Figures 1a and 1d show a surface and cross-sectional SEM images of the 3D copper nanostructure before selective copper electrodeposition. Figure 1b shows a surface SEM image of the 3D copper nanostructure after electrodeposition without additives. The 3D nanostructure was not observed, because copper was deposited on the surface of the 3D nanostructure. The 3D nanostructure seems to have been deformed by the copper deposited on the surface, according to cross-sectional observations (Fig. 1e).Figure 1c shows a surface SEM image of the 3D copper nanostructure after electrodeposition with additives. The surface morphology is almost the same as the bare 3D nanostructure shown in Figure 1a because copper deposition at the surface of the 3D nanostructure is suppressed. Thus, the 3D nanostructure was maintained, and copper was deposited selectively at the boundary of the 3D nanostructure and the substrate, according to cross-sectional observations (Fig. 1f). Agitation also affected the selective copper deposition, and the results of agitation tests will be discussed at the meeting.
References

S. Arai and T. Kitamura, ECS Electrochem. Lett., 3(5), D7-D9 (2014).

Figure 1
Synthesis of Atomically Thin Pt Monolayer on HOPG
Authors: Kuroiwa Eri , Takimoto Daisuke , Nutariya Jeerapat , Shen Zhongrong , Ayato Yusuke , Mochizuki Dai , Sugimoto Wataru 
Published: February 2020

High specific surface area is essential for Pt electrocatalyst. However, nanoparticles become less stable as the particle size decreases. Two-dimensional nanosheets are expected to have comparable or ever larger specific surface area than nanoparticles. Furthermore, nanosheets should be more stable than nanoparticles due to the two-dimensional bonding.
Synthesis of Pt nanosheets with 1 nm thickness has previously been reported1). However, non-reactive Pt atoms still exist in the core of nanosheets, thus the utilization of Pt may be low. The purpose of this research is the synthesis of Pt nanosheets with atomic-scale thickness (nanosheets with 1 or 2 Pt monolayers).
Highly oriented pyrolytic graphite (HOPG) was freshly cleaved using adhesive tape and then immersed into a diluted RuO2 nanosheet colloid for 2 minutes to coat RuO2 nanosheets on HOPG (RuO2 nanosheet/HOPG). Atomically thin Pt monolayer was deposited on the surface of RuO2 nanosheet/HOPG by vacuum evaporation2). Cyclic voltammetry was conducted to dissolve the RuO2nanosheets. The morphology and thickness were characterized by atomic force microscopy (AFM), and the chemical state of the nanosheets on HOPG was determined by X-ray photoelectron spectroscopy (XPS).
Redox peaks at ~0.1, 0.65, 0.8 vs. RHE, which are characteristic of RuO2 nanosheets, disappeared after potential cycling between 0.05 and 1.55 V vs. RHE for 50 cycles, suggesting the dissolution of RuO2 nanosheets. AFM observation showed that the thickness of RuO2 nanosheets were 1.11±0.18 nm and the thickness of the as-deposited Pt on RuO2 nanosheets were 0.34±0.25 nm. Taking into account of the diameter of Pt atom as 0.28 nm, 1-2 monolayer of Pt was deposited on RuO2 nanosheets. The thickness of the nanosheet after cycling decreased to 0.40±0.08 nm, agreeing with the dissolution of the RuO2 support. The chemical state of Pt and Ru before and after electrochemical dissolution was studied by XPS. Pt 4f5/2 and Pt 4f7/2 peaks were observed before and after cycling, while Ru 3p1/2, Ru 3p3/2 peaks disappeared after cycling. Based on CV, AFM and XPS analysis, it is concluded that a Pt monolayer with atomic thickness was successfully prepared on HOPG by using RuO2 nanosheets as a structure directing scaffold and subsequent dissolution of RuO2nanosheets.
1) A. Funatsu, H. Tateishi, K. Hatakeyama, Y. Fukunaga, T. Taniguchi, M. Koinuma, H. Matsuura, and Y. Matsumoto, Chem. Commun., 50, 8503 (2014).
2) Q. Liu, C. Chauvin, and W. Sugimoto, J. Electrochem. Soc., 161, F360 (2014).

Figure 1
Influence of Hydrogen Adsorption on Electrodeposition of Platinum from Chloro Complex Solution
Authors: Yokoyama Ayano , Hagihara Taizo , Fukumuro Naoki , Yae Shinji 
Published: February 2020

Platinum (Pt) is widely used as insoluble and catalytic electrodes for electrolysis, automotive catalytic converters, and fuel cells. We have been investigating hydrogen incorporation in electrodeposited metal films and its influence on crystal structure of metals (1-3). It was reported that large amount of hydrogen (content in atomic ratio: x = H/Pt = 0.1) is incorporated in the Pt films electrodeposited from a solution including dinitrosulfatoplatinate(II) (H2Pt(NO2)2SO4, DNS) as a metal source. In this study, an electrochemical quartz crystal microbalance (EQCM) method (4) is used to examine influence of hydrogen adsorption on the electrodeposition and hydrogen incorporation into deposited films of Pt from a chloro complex solution.
The current-potential and mass increase (Pt deposition rate)-potential curves in 0.024 mol dm-3 K2PtCl4solution adjusted at pH of 0.8 with HCl were measured using an EQCM system (Hokuto Denko, HQ-101D and HZ-5000). A quartz electrode coated with Au, an Ag/AgCl electrode, and a Pt wire were used as the working, reference, and counter electrodes, respectively. The hydrogen content of samples was measured by thermal desorption spectroscopy (TDS).
Figure 1 shows the current density and mass increase rate versus electrode potential curves for the chloro complex solution. In the first forward potential sweep toward negative potentials of Fig. 1(a), the cathode current and deposition rate of Pt started increasing at +0.3 V vs. Ag/AgCl. Peaks for cathode current and deposition rate appeared at -0.19 V. The current efficiency was 74% at this peak. Then, as the potential was swept to lower potentials, the deposition rate and current efficiency decreased. This decrease in the current efficiency of Pt deposition is caused by hydrogen adsorption. In the return potential sweep (Fig.1 (b)), the cathode current and Pt deposition steeply increased by hydrogen desorption from the Pt surface, and the current efficiency was 113% at the potential of -0.25 V. The hydrogen content of Pt-electrodeposited Au foil (Pt: 1 μm and Au: 20 μm in thickness) increased as the deposition potential of Pt decreased from 0 to -0.3 V, and was much lower than that deposited from the DNS solution.

Acknowledgements

The present work was partly supported by JSPS KAKENHI (26289276).

References

N. Fukumuro, M. Yokota, S. Yae, H. Matsuda, Y. Fukai, J. Alloys Compd., 580, S55 (2013).

N. Fukumuro, S. Kojima, M. Fujino, Y. Mizuta, T. Maruo, S. Yae, Y. Fukai, J. Alloys Compd., 645, S404 (2015).

N. Hisanaga, N. Fukumuro, S. Yae, H. Matsuda, ECS Trans., 50, 77 (2013).

T. Hagihara, K. Yaori, K. Iwakura, N, Fukumuro, S. Yae, Electrochim. Acta, 176, 65 (2015).

Figure 1
Electrocatalysts for Oxygen Reduction Reaction Synthesized from Co-Facial Cobalt Porphyrin and Graphene Oxide
Authors: Yoneuchi Tsubasa , Kato Masaru , Yagi Ichizo 
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are used as energy devices, which produce no CO2. Because the Oxygen reduction reaction (ORR) is slow, it limits performance of PEFCs. The ORR involves four-electron reduction (O2 + 4H+ + 4e- → 2H2O) or two-electron reduction (O2 + 2H+ + 2e- → H2O2). The ideal reaction is four-electron reduction. When hydrogen peroxide reacts metal ions in PEFCs, hydroxyl radicals are formed. The radical species induce decomposition of polymer electrolyte membrane in PEFCs. Thereby, the selectivity of the four-electron reduction is an important factor for electrocatalyst development.
In addition, electrocatalysts with higher ORR activity are needed. At the present, platinum group metal alloys (PGMs) are used as ORR electrocatalysts in PEFCs. Since PGMs are expensive and their reserves are limited, electrocatalysts based on earth abundant elements should be prepared. Non-PGM electrocatalysts for the ORR have been intensively studied. For example, Fe- or Co-based electrocatalysts prepared in pyrolysis from carbon and Fe- or Co-based materials.[1,2]These non-PGM electrocatalysts are known to exhibit high catalytic activity for the ORR.
Herein we report the synthesis of a non-PGM electrocatalyst with co-facial cobalt active sites and its catalytic activity and selectivity for the ORR. The catalyst was prepared in the pyrolysis process at 900oC for 45 s from two precursors: graphene oxide and a co-facial cobalt porphyrin ion pair. The co-facial cobalt porphyrin ion pair have high selectivity of the four-electron reduction.[3,4] To study the ORR catalytic activity and selectivity, linear sweep voltammetry of the electrocatalyst was recorded at three pHs (pH 1, pH 7, and pH 13) under oxygen. The ORR activity improved with increasing pH and the activity at pH 13 was higher than that of Pt/C. The electrocatalyst showed the highest four-electron selectivity (< 10% H2O2) at pH 13.
We conclude that the ORR activity and selectivity of the electrocatalyst are improved by pyrolysis process.
References
[1] K. Kamiya, K. Hashimoto, S. Nakanishi, Chem. Commun., 48, 10213-10215(2012).
[2] G. Wu, K. L. More, C. M. Johnson, P. Zelenay, Science, 332, 443-447(2011).
[3] J. P. Collman, P. Denisevich, Y. Konai, M. Marrocco, C. Koval, F. C. Anson, J. Am. Chem. Soc., 102, 6027-6036(1980).
[4] A. J. Olaya, D. Schaming, P. F. Brevet, H. Nagatani, T. Zimmermann, J. Vanicek, H. J. Xu, C. P. Gros, J. M. Barbe, H. H. Girault, J. Am. Chem. Soc., 134, 498−506(2012).
Fabrication of Electrochemically Controllable Micropumping System Based on Concentration Gradient of Protons Between Two Gold Microelectrodes
Authors: Fujiwara Hiroki , Shitanda Isao , Hoshi Yoshinao , Itagaki Masayuki , Motosuke Masahiro 
Published: February 2020

Design of a micropump is important topic for controlling solution flow in a microchip 1). In this study, we newly fabricated a new electrochemically controllable micropumping system which operates by creating a concentration gradient of protons on two gold microelectrodes. Figure 1 show a schematic illustration of the principle of the pumping system. When anodic and cathodic reactions of hydrogen peroxide occurs on the each gold electrode surface, protons generated on the anode flow thorough the cathode. The protons are normally hydrated in an aqueous solution. Thus, localized water flow generates near the gold microelectrode surfaces.
The gold microelectrodes (5 נ100 um2) were fabricated by photolithography. A microchannel in a microchip was formed by using polydimethylsiloxane (PDMS, 500 um width, 50 um height, 2.5 cm length). 5% hydrogen peroxide solution containing fluorescent substance- modified polystyrene (PS) particle was filled in the microchannel. A polarization curve was measured by using a potentiostat. Current increase was observed from 0 V. Current noise due to oxygenbubble generation occurred when applying the voltage of 0.6 V. Thus the moving direction of the polystyrene particles were observed using a fluorescent microscope while applying a constant voltage of 0.5 V between the gold microelectrodes. PS particles were adsorbed electrostatically on the anode surface when applied a constant voltage of 0.5 V. Next, when stopping the voltage application, the PS particles drastically moved opposite direction of the proton flow (Fig. 1). It is considered that the PS particles moved due to the reaction of water flow 2). We discussed in the moving principle more detail in our presentation.
Reference
1) H. Zhang, W. Duan, M. Lu, X. Zhao, T. J. Huang and A. Sen, Acs Nano, 8 (2014) 8537-8542.
2) J. Wang, Acs Nano, 3 (2009) 4-9.

Figure 1
Screen-Printed Paper-Based Impedimetric Sensor Using Flexible Silver Ink for Sweat Conductivity Measurement
Authors: Watanabe Kazuki , Shitanda Isao , Hoshi Yoshinao , Itagaki Masayuki 
Published: February 2020

Recently, electrochemical wearable devices have been attracted attention as a device for evaluating the health condition. Flexibility of a substrate and conductive wiring with low cost is key point to attach the sensor on the human body . Our group has reported several paper-based biosensor and biofuel cells [1,2]. A printable paper-based devise is suitable for disposable wearable sensors.
In this study, we newly prepared a flexible silver ink as a conductive wiring, and a flexible electrochemical impedimetric sensor was fabricated by screen printing using Japanese paper with surgical tape as the substrate for measurement of sweat conductivity. Flexible silver ink was prepared by mixing a silver flakes (Fukuda Metal Foil Powder Co.) and a urethane resin (Dispercoll U42, Sumika Bayer Co. Ltd.) with a commercially available silver ink. Figure 1 shows the schematic illustration of the sensor. Silver wiring was prepared by printing of the flexible silver ink mentioned above on the surgical tape having two holes. The durability of the silver wiring was evaluated by bending test, in which the silver wiring was bended with a constant curvature at 50 times. Commercially available carbon ink was printed on the Japanese paper as a sensor part. It is noted that the carbon layer and silver wiring were connected through the holes on the surgical tape. A conductivity of a test solution (artificial sweat) in the paper was determined by electrochemical impedance measurement. The conductivity of the solution was compared with that estimated using a commercially available conductivity meter (Toa DKK made, CM-25G). The durability of the silver wiring using the silver flake and urethane resin was drastically improved, comparing with that using only commercially available silver ink. The increasing rate of the resistance of the silver wiring using the silver flake and urethane resin after the bending test was 260%. On the other hand, that using only the commercially available silver ink was 580%. Cracks on the silver wiring were found to be suppressed by using the urethane resin. The silver flakes have a role as a binder to connect between silver particles in the ink. The conductivity of the artificial sweat in the paper measured by the sensor was good agreement with that measured by the conductivity meter. Furthermore, in the present paper, we measured change in a human sweat conductivity during the exercise using our wearable sensor.
References
[1] S. Kato, et al.
Chem. Commun.
, 2013,49, 11110-11112
[2] T. Yamaguchi, et al. Chemistry Letters, 2013, 42, 1369-1370

Figure 1
Influence of Cathode Catalyst Layer Structure on PEFC Performance Using Two-Dimensional Carbon Support for Pt Catalyst
Authors: Kachi Kazuhiro , Shimada Iori , Osada Mitsumasa , Takahashi Nobuhide , Fukunaga Hiroshi 
Published: February 2020

Introduction
Polymer electrolyte fuel cell (PEFC) has been attracting much attention due to its high efficiency at low operating temperature. However, since platinum (Pt), which is used for the electrode catalyst in the cathode, is a metal of low abundance and high cost, reduction of the Pt usage is required. Generally, nano-size Pt particles supported on carbon black are used to increase the mass activity. However, nanoparticles have problems in durability. Moreover, since some Pt particles are located inside the pore of the support, diffusion of supplied oxygen and produced water are suppressed. Recently, nanostructured thin film (NSTF)1) and Pt thin film fabricated by atomic layer deposition (ALD)2) are reported as alternative catalysts. However, they are fabricated on non-conducting materials. Takenaka et al. fabricated metal oxide nanofilms using graphene oxide (GO) as a template to form two-dimensional (2-D) catalysts3). 2-D catalysts are expected to show high mass activity due to the high surface area, and high conductivity during power generation due to the reduced GO and/or metal oxide. In this study, membrane electrode assembly (MEA) was prepared using Pt/GO catalyst, and the relationship between the performance and the structure of the electrode catalyst layer using 2-D carbon support for Pt catalyst was investigated to obtain information towards low Pt loaded PEFC.
Experimental Catalyst inks were prepared by mixing Pt /Graphene oxide (Pt/GO), carbon black (CB), n-Propyl alcohol, and distilled water, and then the mixture was sonicated. 5 wt.% Nafion® solution was added to the mixture which was sonicated again. Catalyst ink was mixed by rotation revolution mixer. Then it was coated onto polytetrafluoroethylene (PTFE) sheet using doctor blade method to fabricate catalyst layer (CL). CL and Pt/carbon paper were hot-pressed onto each side of the Nafion® membrane. After the PTFE sheet was peeled off, carbon paper was hot-pressed onto CL to fabricate the MEA. Terminal voltage vs. current density of the MEA was measured at 80 ˚C.
Results and Discussion
Terminal voltage vs. current density of MEA with various ionomer/carbon ratios (I/C) using Pt/GO are shown in Fig. 1. As it can be seen in the figure, the cell performance in the low current density region was higher when I/C was higher. This indicates that reactive sites have increased due to the coating of catalyst by ionomer. On the other hand, MEA prepared with low I/C showed higher cell performance in the high current density region. It is considered that ohmic resistance was reduced due to the thin coating of catalyst by ionomer.
References
1) M. K. Debe, J. Electrochem. Soc, 160 (6), F522-F534 (2013)
2) M. Inaba, T. Suzuki, T. Hatanaka, Y. Morimoto, J. Electrochem. Soc, 162 (7), F634-F638 (2015)
3) S. Takenaka, S. Miyake, S. Uwai, H. Matsune, M. Kishida, J. Phys. Chem. C, 119 (22), 12445-12454 (2015)

Figure 1
Novel Ir@Pt Core@Shell Nanoparticles As Catalysts for Ethanol Oxidation
Authors: Slaby Jachym , Ketabi Sanaz , El Sawy Ehab , Birss Viola 
Published: February 2020

Ethanol is a promising fuel for transportation applications, given its low toxicity and easy access from feedstock fermentation. However, the combustion of ethanol to regain the stored energy is highly inefficient and thus a non-combustion process, such as the electrochemical oxidation of ethanol in a fuel cell, is desirable for utilizing the stored energy. To achieve high conversion efficiencies, an appropriate catalyst for ethanol oxidation must be developed. While Pt is a good material for this purpose, it is prone to poisoning by strongly adsorbed intermediates, e.g., CO. To address these shortcomings, Pt can be nanostructured and combined with other metals, resulting in superior activity and longer lifetimes.
In the present work, Ir core@Pt shell nanoparticles (NPs) were synthesized, with varying Pt shell coverages (less than one monolayer), ensuring that some Ir is exposed and thus allowing the bifunctional effect [1], electronic [2], and strain effects [3] to all play a role in the catalysis of the ethanol oxidation reaction. The core@shell NPs were synthesized using the polyol method [4], producing a core that was ca. 3 nm in diameter and then loaded (10 mass %) onto Vulcan Carbon powder. These catalysts were then characterized by wavelength-dispersive X-ray spectroscopy (WDS) and thermogravimetric analysis to determine the relative percentage of each metal present in each nanoparticle and to confirm the metal loading onto the carbon, respectively, while TEM analysis confirmed the expected NP size and distribution.
The electrocatalytic activity of these materials was evaluated using a three electrode system, all in 0.5 M H2SO4 + 0.01 - 1 M ethanol at room temperature. Overall, it is shown that these Ir core@Pt shell NPs are notably more active than Pt NPs of the same size and also produced using the polyol method. The activity of the catalysts increases with ethanol concentration, but less than linearly, and sweep rate studies revealed the presence of electroactive surface-bound reaction intermediates. The stability of the catalysts has also been investigated using cyclic voltammetry and chronoamperometry experiments. By studying the effect of Pt shell coverage on the Ir core NPs, the mechanism by which Ir enhances the activity of Pt during ethanol oxidation is now being determined.
References:

El Sawy, E. N.; Molero, H. M.; Birss, V. I. Electrochimica Acta (EAST13-0480)
2013.

Chen, Y. M.; Yang, F.; Dai, Y.; Wang, W. Q.; Chen, S. L. Journal of Physical Chemistry C
2008, 112, 1645-1649.

Zhang, X. T.; Wang, H.; Key, J. L.; Linkov, V.; Ji, S.; Wang, X. L.; Lei, Z. Q.; Wang, R. F. Journal of The Electrochemical Society
2012, 159, B270-B276.

Alayoglu, S.; Eichhorn, B. Journal of the American Chemical Society
2008, 130, 17479- 17486.