bluuebunny/crossref_metadata_2025_split huggingface dataset:
Na3Zr2Si2PO12-Polymer Hybrid Composites for Solid-State Supercapacitor Applications
Authors: Dinachandra Singh Mayanglambam , Dalvi Anshuman , Phase D M 
Published: May 2020

Various Na+ ions conducting composite polymer electrolytes have been developed in last three decades, but their application is limited due to poor ionic conductivity near room temperature. Recently, we have demonstrated high ionic conductivity of ∼ 10-4 Ω-1cm-1 in NASICON-polymer hybrids and found these systems useful in energy storage applications. A high ionic mobility of ~ 10-1 cm2/V-s was also reported. Present work shows a possible application of these hybrids as electrolyte/separator in all-solid-state supercapacitor.
In this work, Na+ NASICON, viz. Na3Zr2Si2PO12 (NZSP) have been prepared by conventional solid state reaction route. Subsequently, their nanoparticles of size ~ 30 nm were obtained via mechanical ball milling. The nanoparticles were mixed with polymer in a ball mill until a homogeneous viscous slurry formation. Further the slurry was dried, hot pressed at ~ 80°C to obtain films of uniform thickness ~ 250µm. This way, composite films with composition (wt%) 10NaI-90(PEO1-xNZSPx), where 0 ≤ x ≤ 0.4, were obtained. Surface morphology, structural and thermal analysis were characterized using FESEM, XRD and DSC. A maximum ionic conductivity of ~ 4 x 10-5 Ω-1cm-1 at room temperature has been achieved for composite with x = 0.4. Impedance spectroscopy was used to understand mechanism of ionic transport. Further, to understand the role of ceramic fillers in enhancing the ionic conductivity, local structure of the composites was studied using x-ray absorption near edge structure spectroscopy (XANES) at Indus II Beamline 01, RRCAT, Indore. These results suggest a significant role of NASICON in providing pathways for Na+ ion transport.
The ionic conductivity at room temperature for composite with x = 0.4 were further modified with EMITf and EC+PC as plasticizer. A maximum ionic conductivity of ~ 2 x 10-4 Ω-1cm-1 at room temperature has been achieved with addition of 2 wt% of EMITf in the composite. To elucidate the capacity of these electrolyte as a membrane for all solid-state ionic devices, solid state super capacitors (configuration C|CPE|C) were fabricated. These composites have been found to be competitive candidates for energy storage. A maximum specific capacitance of ~ 26 F-g-1 is obtained for composite with 2 wt% EMITf at room temperature.
Integrating Multiple Advantages into 1 Nm Pt3Ni Bimetallic Alloy Nanowires for Oxygen Reduction Reaction
Authors: Deng Zhiping , Wang Xiaolei 
Published: May 2020

Exploiting highly active and durable oxygen reduction reaction (ORR) electrocatalyst is still imperative for clean and efficient energy conversion device, such as fuel cells and metal-air batteries. For this purpose and maximize the utilization of noble Pt, we present here a facile, scalable strategy for the high-precise synthesis of 1 nm thick Pt3Ni bimetallic alloy nanowires (Pt3Ni BANWs). The seed-mediated growth mechanism of Pt3Ni BANWs is identified by examining the morphology and composition of the intermediate products collect at different reaction stages. As expected, the Pt3Ni BANWs delivered enhanced mass activity (0.546 A mg-1
Pt, exceeding the DOE 2020 target) in comparison to Pt nanowires assembly (Pt NWA, 0.098 A mg-1
Pt) and Pt/C (Pt, 0.135 A mg-1
Pt) due to the rational integration of multiple compositional and structural advantages, such as alloy feature, ultrathin 1D nanostructure and high-index facets. Moreover, the Pt3Ni BANWs displayed enhanced durability (37% MA retention) than Pt NWA and Pt after 50,000 potential cycles. All these results indicate that the ultrathin Pt3Ni BANWs are potential candidates for catalyzing ORR with acceptable activity and durability. The present work could not provide a facile strategy but also a general guidance for the design of superb performance Pt-based nanowire catalysts for ORR.

Figure 1. Progressive formation mechanism of the ultrathin Pt3Ni BANWs.

Keywords: Oxygen Reduction Reaction, Pt-Ni alloy, Nanowires, Seed-mediated growth

References:

[1] Stamenkovic, V. R.; Fowler, B.; Lucas, C. A.; Marković, N. M. Improved oxygen reduction activity on Pt3Ni (111) via increased surface site availability. Science
2007, 315, 493-497.
[2] Xiao, W.; Gong, M.; Xin, H. L.; Wang, D. Recent advances of structurally ordered intermetallic nanoparticles for electrocatalysis. ACS Catal.
2018, 8, 3237-3256.

Figure 1
Electrolyte Concentration Variation during Pulsed Potential Electrochemical CO2 reduction to Control Product Selectivity
Authors: Casebolt Rileigh , Kimura Kevin Wayne , da Silva Jessica Akemi Cimada , Kim Jiyoon , Suntivich Jin , Hanrath Tobias 
Published: May 2020

One of the grand challenges in electrocatalysis is to better understand the factors that determine activity and selectivity to control the precision of electrochemical reactions.1 Electrocatalytic CO2 reduction (eCO2R) is a prototypical example of such a reaction, where control over product selectivity would completely transform electrosynthesis processes. Beyond the pursuit of fundamentally understanding electrochemical catalysis, development of eCO2R is driven by growing concerns about global CO2 emissions and the quest for valorization of captured CO2. However, product selectivity and electrocatalyst longevity persist as obstacles to broad implementation of eCO2R. One possible solution to address this challenge is to apply a pulsed potential during eCO2R, which creates a stable reduction environment and tunable product selectivity.2 We leveraged this long-term product stability of pulsed potential eCO2R to examine the relationship between electrolyte concentration and composition with product selectivity for a copper electrode. Whereas constant potential experiments suffer from quick degradation as selectivity towards CO2 reduction products lasts only on the order of one hour, pulsing the potential maintains robust selectivity over 24 hours. This stability presents a unique opportunity to vary the electrolyte parameters while keeping experimental conditions consistent thereby eliminating electrode variability. We find the relation of electrolyte concentration and composition differs greatly for constant and pulsed potential eCO2R. In the case of constant potential eCO2R, increasing KHCO3 concentration is known to favor the formation of H2 and CH4. In contrast, for pulsed potential eCO2R, H2 formation is suppressed due to the periodic adsorption of surface hydroxides, while CH4 is still favored. In the case of KCl, increasing the concentration during constant potential eCO2R does not affect product distribution, mainly producing H2 and CO. However, during pulsed potential eCO2R, increasing KCl concentration suppresses H2 evolution and greatly favors C2 products, reaching 71% Faradaic efficiency. Collectively, these results provide new mechanistic insights into pulsed potential eCO2R in context of the ionic conductivity and higher presence of surface hydroxides which promote C-C bonding. More broadly, the techniques employed here can be used to understand and optimize other electrosynthesis processes.
[1] Bell, A. T.; Gates, B. C.; Ray, D.; Thompson, M. R. Basic research needs: catalysis for energy; Pacific Northwest National Lab.(PNNL), Richland, WA (United States): 2008.
[2] Kimura, K. W.; Fritz, K. E.; Kim, J.; Suntivich, J.; Abruña, H. D.; Hanrath, T., Controlled Selectivity of CO2 Reduction on Copper by Pulsing the Electrochemical Potential. ChemSusChem
2018,
11 (11), 1781-1786.
Rational Design of Copper Alloy Catalysts for Electrochemical CO2 Reduction
Authors: Akhade Sneha A , Weitzner Stephen Eric , Qi Zhen , Biener Monika M. , Varley Joel Basile , Baker Sarah E , Duoss Eric B , Wood Brandon C. , Biener Juergen 
Published: May 2020

Electrochemical conversion of CO2 is a potentially exciting route towards production of sustainable drop-in fuels and chemicals using renewable electricity. A key obstacle in the commercial scale-up and deployment of CO2 utilization and conversion is the lack of active and selective catalysts. Across all monometallic candidates, Cu exhibits distinctive ability to electrochemically reduce CO2 to several products including methane and ethylene, albeit its multifunctional nature makes selectivity control challenging [1]. Alloying offers a means to break scaling relationships and uniquely manipulate the reactivity and selectivity in ways that would be hard to achieve using monometallic compositions alone. Here, we employ a coupled quantum mechanics/molecular mechanics (QM/MM) scheme [2] to screen various copper alloys for their reactivity and selectivity towards key rate-limiting and selectivity-determining steps in CO2 conversion. The activity-selectivity screening is carried out under reducing conditions to thoroughly probe the influence of the electrolytic ions under the applied potential on the alloy stability and reactivity. The results of these studies show how alloying in conjunction with electrolyte tuning can non-intuitively alter the surface electronic and catalytic properties of the catalyst leading to changes in activity-selectivity towards CO2 conversion. This serves to provide a rationale for improved composition and environment driven design and screening, and allows the use of chemical computation using nuanced, dynamical models of the electrochemical double layer[i].
[1] Y. Hori, in Handbook of Fuel Cells: Fundamentals, Technology and Application (VHC Wiley, Chichester, 2003), Vol. 2, 720-733.
[2] J. Haruyama, T. Ikeshoji and M. Otani, Electrode potential from density functional theory calculations combined with implicit solvation theory. Physical Review Materials (2018), 2(9), p.095801.

[i] This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
High-Throughput Screening of Hydrogen Peroxide (Electro)Catalysts Using Scanning Electrochemical Microscopy (SECM)
Authors: Zhao Yuanya , Kromer Matthew , Adams Jason , Flaherty David , Rodriguez-Lopez Joaquin 
Published: May 2020

Hydrogen peroxide (H2O2) is a powerful, versatile and environmentally benign oxidant that has gained relevance in industrial settings. Direct synthesis of H2O2 from O2 and H2, which is a method with low pollution and on-site production at potentially low cost, has attracted great interest. To realize this synthetic process, catalysts of high efficiency need to be developed to facilitate the reaction. In this study, scanning electrochemical microscopy (SECM) methods were used to conduct high-throughput screening of bimetallic nanoparticle catalysts (consisting of Au, Pt, Ni, etc.) for H2O2 generation from direct synthesis. In order to achieve high-throughput analysis, samples with multiple catalysts were fabricated. We used photolithography to produce wells that confined catalyst spots of a library of materials. Gold nanoparticles (AuNPs) were dispensed into these wells with a microdispenser, leaving the same amount of AuNPs at each spot. Droplets of corresponding metal salt solutions were added into the wells and then annealed to form bimetallic catalyst spots. The morphology and composition of fabricated spot arrays were characterized with SEM, TEM and EDS.
SECM measurements were performed to study the catalytic reactivity of the catalyst spots for H2O2 direct synthesis. From an electrochemical point of view, the entire process of H2O2 direct synthesis from H2 and O2 can be split into two half reactions, oxygen reduction and hydrogen oxidation. The first half reaction, oxygen reduction reaction (ORR), is a two-electron process reducing O2 into H2O2. The second half reaction, hydrogen oxidation reaction (HOR), converts H2 to protons. Only when a catalyst exhibits outstanding catalytic reactivity towards both two reactions, does it catalyze H2O2 direct synthesis efficiently in a thermocatalytic system. The catalytic reactivity for the two half reactions was investigated separately in a high throughput manner by SECM as the technique acquired information from the entire spot array in one scan and revealed catalytic performance for each spot in the array. SECM images were obtained to visualize catalytic reactivity of the spot array.
Finite element analysis simulation was done in COMSOL Multiphysics to acquire theoretical values for SECM experiments. The ultimate goal of this study is to identify a catalyst of a specific composition with the best catalytic reactivity for overall H2O2 direct synthesis. Such catalyst can be used in industrial H2O2 production to improve production efficiency and to reduce cost.
Accessing Catalytically Active Ordered Intermetallics Compounds Via Electrochemically Driven Phase Transformations
Authors: Hall Shoji 
Published: May 2020

The conversion of O2 to H2O is an important fuel cell reaction for the recovery of renewable electricity from chemical fuels. Alloys of Pt-group metals (PGMs) with transition metals have emerged as catalysts with enhanced activity and durability for the oxygen reduction reaction (ORR). To date, most studies focus exclusively on alloys that adopt a Face-centered cubic (FCC) or Face-centered tetragonal (FCT) crystal lattice. Under ORR operating conditions, these materials evolve from alloys to Pt core-alloy shell materials, in this case both the alloy core and Pt shell retains the CCP type crystal structure; indicating that materials can dynamically change during catalysis.
Here we present the synthesis of Pd-Bi based ordered intermetallics by partial dealloying of a Bi rich alloy. We found that under ORR operation conditions, ß-PdBi2 which adopts a tetragonal lattice, transforms to Pd3B orthorhombic crystal structure; this transformation is mediated by oxidative Bi corrosion under potential cycling, and reconstruction of the atoms in the bulk. To the best of our knowledge, this is the first report of a material that exhibits an electrochemically driven, non-congruent phase transition among materials with different crystal structures. The resulting phase-converted Pd3Bi is stable and exhibits high performance for ORR. Phase-converted Pd3Bi outperform Pt and Pd metal, reaching mass activities of 2.6 A/mgPd, which is nearly 10X higher than Pt/C (~0.3 A/mgPt) and Pd/C (~0.2 A/mg) at 0.9 V vs the Real Hydrogen Electrode (RHE). The mass activity of Pd3Bi decreases by ~38% after 10,000 cycles, indicating that it is stable. Activation energy (Ea) determined by temperature dependent electro-kinetic measurements indicates that the activity enhancement on phase-converted Pd3Bi originates from anion-poisoning resistant behavior. These results establish that PGMs-based ordered intermetallics with low-symmetry crystal structures can be highly active and durable electrocatalysts.
Bio-Inspired Heterogeneous Catalytic Cascades
Authors: Atanassov Plamen 
Published: May 2020

Bio-electrochemistry research in our group has been focused on building suitable materials and design of interfaces to accommodate biocatalysts, both enzymatic and microbial for most advantageous utilization in sensing, energy harvesting and water treatment technologies. Over the years we have demonstrated several enabling materials design approaches to address critical challenges in bio-electrocatalysis: facilitating charge transfer through tethering immobilization, enzyme orientation, hierarchically structured nano-materials integrated into device design, immobilization by encapsulation in polymer and silica matrixes and development of hybrid microbial/enzymatic and microbial/platinum group metal-free bio-electrochemical devices.
A critical challenge in building complex bio-nano-devices is the ability to combine several catalytic reactions into a “cascade” with channeling as underlying principle for effective multi-step catalysis.1One particularly complex area of our research over the last yeas has been in development of materials solutions for catalytic cascades, which would integrate bio-catalysis with molecular and heterogeneous catalytic steps.2-4We are currently engaged in a large program directed towards bringing together functional catalysts from the most distinctly different types: enzymes, molecular catalyst and metallic nanoparticles into a singular functional interface for realization of cascade reactions catalyzed by all these different species/moieties. We will illustrate the approach by discussing the synthesis of a hybrid enzyme/metal nano-particle/atomically-dispersed nano-material functional catalyst cascade.
This bio-inspired catalytic cascade aims to demonstrate the possibility of assembling heterogeneous catalytic reactions in sequence while the catalysts of three dissimilar classes are all immobilized on a 2D nanomaterial (graphene). The paper aims to bring a vision of building bio-electrochemical devices, where enzymatic catalysis will be enhanced by the heterogeneous and molecular one, with all catalytic moieties co-present at a single “designer interface” based on graphene-like carbonaceous material. This material allows ease of integration by printing into a paper-based microfluidic analytical platform designed for a confocal Raman microscope with in situspectro-electrochemical detection.5,6

1. Wheeldon, I., et al., Nature Chemistry,8 (2016) 299–309
2. Abdellaoui,S., et al., Chemical Communications, 53(2017) 5368-5371
3. Xia, L., et al., ACS Energy Letters., 2 (2017) 1435-1438
4. Perry, A., et al., ChemElectroChem, 4 (2017) 2336-2344
5. Andersen, N., et al., ChemElectroChem, 6 (2019) 246-251
6. Andersen, N., et al., ChemElectroChem, 6 (2019) 2448–2455

Figure 1
Magnetic Filling of Microporous Silicon: An Interlink of Optical and Magnetic Behavior
Authors: Granitzer Petra , Rumpf Klemens , Reissner Michael , Michor Herwig 
Published: May 2020

In the frame of this work microporous silicon (mPSi) is filled with magnetic metals (Ni, Co) resulting in a composite system with specific magnetic properties. The results are compared with mesoporous silicon (PSi) loaded with Ni nanoparticles (NPs) of comparable size. The mPSi offers luminescence in the visible, whereat this behavior is due to the small structure size in the range of a few nanometers (2 – 5 nm) [1]. The morphology of mesoporous silicon shows straight pores with a diameter up to 50 nm.
The mPSi samples are fabricated by anodization of a moderately doped p-type silicon wafer in a 10 wt% hydrofluoric acid solution. The challenging metal filling of these pores is carried out under cathodic conditions by pulsed electrodeposition. As electrolytes aqueous NiSO4 and CoSO4 solutions are employed. The microporous silicon offers a branched morphology and thus also the deposited nanosized metal structures are interconnected. The structure size of the porous samples is estimated by photoluminescence measurements to 5 nm which also determines the size of the deposits. Mesoporous silicon is produced by anodization of a highly n-doped silicon wafer resulting in straight pores of about 50 nm in diameter [2]. The loading of these samples with Ni NPs is also performed by electrodeposition.
Magnetic filling of meso- and microporous silicon, respectively means a change in the morphology as well as in the structure size of the magnetic precipitations and both influence the magnetic behavior of the composite system drastically. In the case of mPSi also the luminescence is influenced in its intensity and wavelength by the magnetic filling. The magnetic properties are investigated with a Vibrating Sample Magnetometer (VSM) and a SQUID, respectively. A luminescence spectrometer is used to measure the intensity and the peak position of the photoluminescence spectrum. The structure is investigated by SEM and TEM.
Field dependent magnetization measurements show a distinct difference between Ni filled mPSi and PSi loaded with Ni NPs. Considering mPSi filled with Ni and Co a strong magnetic anisotropy between the two magnetization directions applying a magnetic field perpendicular and parallel to the surface, respectively is observed, whereas in the case of Co this behavior is even more pronounced. Figure 1 depicts the hysteresis of mPSi and mesoporous silicon filled with Ni. The coercivities do not vary in a broad range between Ni and Co samples but the saturation field differs drastically between the two materials. In contrast mesoporous silicon loaded with Ni NPs offers only a small magnetic anisotropy caused by weak magnetic interactions between the Ni deposits.
Since the microporous silicon offers photoluminescence the huge magnetic anisotropy is of interest for magneto-optical applications.
[1] Handbook of Porous Silicon, Ed. L. Canham, Springer Int. Publishing, 2018.
[2] P. Granitzer, K. Rumpf, Semiconductor Science and Technology 31, 4004, 2016.

Figure 1
Hard Magnetic Composite: FePt Nanoparticles Grown within Nanostructured Silicon
Authors: Rumpf Klemens , Granitzer Petra , Gonzalez-Rodriguez Roberto , Coffer Jeffery , Reissner Michael 
Published: May 2020

In this work porous silicon (PSi) and silicon nanotubes (SiNTs) are presented as a platform for filling with FePt nanostructures which offer a hard magnetic behavior. The difference of the magnetic characteristics between the two systems is figured out.
The porous silicon is produced by anodization of a highly doped n-type silicon wafer in a 10 wt% HF solution [1]. The morphology offers separated pores of about 60 nm and a mean distance between the pores of 50 nm. The SiNTs are fabricated in using an array of ZO wires as template, subsequent silicon deposition and finally etching off the ZO [2]. The inner diameter of the tubes and also the wall thickness can be tuned by the fabrication process. In this work SiNTs with comparable inner diameter to the PSi structure are used. FePt nanoparticles (NPs) are chemically grown inside the pores and the tubes, respectively whereat the molar ratio of Fe is varied (Pt:Fe 1:1, 1:3 and 1:6). For this purpose a 3 component solution consisting of H2PtCl6, Fe(NO3)3 and citric acid is used, whereas the ratio of the components is modified.
Magnetic characterization of the samples is performed by VSM (Vibrating Sample Magnetometer), the structure is analyzed by SEM, TEM and EDX.
The magnetic response of the two different composite systems is investigated. PSi/FePt shows a higher coercivity and remanence than SiNTs/FePt and thus a higher hard magnetic performance. The variation of the coercivities between SiNTs/FePt and PSi/FePt is about 57%.
Considering the FePt deposits with different molar ratio of Fe the coercivities vary in a range of 5% in the case of both template types. Comparing FePt loaded samples with Co loaded samples in all cases an increase of the coercivity and of the remanence is observed for FePt, whereat in the case of PSi as template material the increase is significantly stronger than in the case of SiNTs samples. Figure 1 shows the comparison of the hysteresis of PSi and SiNTs filled with FePt NPs.
Hard magnetic materials within nanostructured silicon give rise for on-chip applications using 3 dimensional arrays of nanomagnets.
[1] K. Rumpf, P. Granitzer, H. Michor, NRL 11, 398 (2016).
[2] X. Huang, R. Gonzalez-Rodriguez, R. Rich, Z. Gryczynski, J.L. Coffer, Chem. Comm. 49, 5760 (2013).

Figure 1