bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Bimetallic Electrocatalysts for Electrochemical CO2 Reduction
Authors: Ismail Ahmed Mohsen , Csapo Edit , Janáky Csaba
Published: May 2020

Bimetallic nanoparticles (NPs) offer great flexibility to tailor the activity and selectivity in electrocatalytic conversion of carbon dioxide (CO2) to valuable chemicals. Here, we report on the electrocatalytic behavior of Au-Sn, Au-Ag and Au-Pb NPs, to highlight the effect of the intermetallic phase formation and the bimetallic composition in CO2 electroreduction.

Firstly, a series of Au–Sn electrocatalysts with different intermetallic phases were obtained via tin incorporation into the gold lattice through gradual diffusion. Stoichiometric intermetallic phases were formed, and under optimal conditions, two high-value products formed with reasonable current density: formic acid in the liquid phase and syngas in the gas phase. Notably, the phase composition had a massive influence on both the activity and the product distribution. In situ Raman spectroelectrochemistry studies demonstrated that catalytic performance of the AuSn phase was superior to that its parent metals and other bimetallic counterparts.

Secondly, the correlation between the electrocatalytic activity and the composition of Au-Ag alloy NPs was studied. The CO Faradaic efficiency (and thus the forming CO:H2 ratio) was changed linearly by controlling the Au:Ag ratio in the alloy. This trend was attributed to the changes in the electronic properties, as there was a monotonous shift in the Fermi level away from the vacuum level with increasing Au content. This shift correspondingly reduces the binding energy of the intermediates (*COOH and *CO), resulting in the gradually enhanced CO2-reduction activity.

Finally, I will show results gained with Au-Pb electrodes, where the formation of methane (CH4) was demonstrated. Factors underpinning this unusual behavior were studied by both experimental and theoretical means.
(Invited) Highly Durable Platelet-Type Carbon Nanofibers for Oer in Alkaline Electrolyte
Authors: Sato Yuki , Kowalski Damian , Aoki Yoshitaka , Habazaki Hiroki
Published: May 2020

Porous anodic alumina films formed by anodizing of aluminum in acid electrolytes have a highly ordered, nanopore channels, which have attracted increased attention as template for various nanomaterials. Utilizing this template, platelet-type carbon nanofibers (pCNFs) have been successfully prepared by simply heating a mixture of the template and polymer powders, such as polyvinyl chloride and polyvinyl alcohol, in argon atmosphere via liquefied intermediate of the polymers (1, 2). The graphitization degree of pCNFs increases with annealing temperature, and interestingly, the neighboring reactive carbon edge sites at the sidewall of pCNFs form loops of several carbon layers at above 2000ºC. Here, we demonstrate that such pCNFs with high graphitization degree and loop structure exhibit extremely high oxidation resistance under oxygen evolution reaction (OER) conditions in highly alkaline electrolyte for a zinc-air secondary battery application.

During galvanostatic OER on the state-of-the-art highly active Ca2FeCoO5 electrode with a conventional carbon black conductive agent in 4 mol dm-3 KOH electrolyte consumed the carbon black almost completely within a few days, whereas that with pCNFs annealed at 2400ºC exhibited almost no consumption of the pCNFs even after one month. The carbon nanofibers with platelet structure and high graphitization degree are promising for the air electrode materials in a zinc-air battery.

Acknowledgment

This work was supported in part by the RISING2 (Research and Development Initiative for Science Innovation of New Generation Batteries 2) of the New Energy and Industrial Technology Development Organization (NEDO), Japan.

1. H. Konno, S. Sato, H. Habazaki and M. Inagaki, Carbon, 42, 2756 (2004).

2. H. Habazaki, M. Kiriu, M. Hayashi and H. Konno, Mater. Chem. Phys., 105, 367 (2007).
Electrocatalytic Metallic Nanostructures Prepared By Electrorefining and Cathodic Corrosion
Authors: Michalak Magdalena , Kalisz Justyna , Roguska Agata , Opallo Marcin , Nogala Wojciech
Published: May 2020

Metallic nanostructures (NS) due to their unique properties are often used as electrocatalytic electrode materials in energy conversion and storage as well as in sensing applications. Their common methods of preparation involve homogeneous synthesis and electrodeposition from solutions containing appropriate precursor and often reducing agent and capping agent (surfactant). The main drawbacks of these methods are restricted yield, waste production and often intrinsic contamination of the surface of obtained NS. Moreover, surface capping ligands affect electrocatalytic activity by hindrance of reactant access to the active sites.

We propose a versatile method of preparation of bare (non-capped) mono- and multi-metallic (Au,1 Cu,2 Ag, Fe) NS by localized electrorefining of polycrystalline raw metals at high efficiency in a controlled manner. Catalytic activities of obtained NS towards oxygen reduction reaction (ORR) in alkaline media, hydrogen evolution (HER) and carbon dioxide reduction (CO2RR) to easily electrooxidizable fuels (formic acid and carbon monooxide) were analyzed by feedback mode scanning electrochemical microscopy (SECM). The morphology and specific activity of obtained NS depend on used support material (indium tin oxide (ITO) and glassy carbon) and other electrorefining parameters such as electrodeposition potential, source velocity and the composition of the electrolyte. The last parameter determines stoichiometry of Faradaic processes. Both gold and copper electrooxidation and electroreduction can follow one electron stoichiometry. ORR in alkaline media and CO2RR occur effectively on NS with highly developed surfaces, containing large number of defects, corners and edges, whereas HER occurs efficiently at crystallographic Cu facets. Bare gold NS also exhibit outstanding plasmonic properties. They were applied as support for surface-enhanced Raman spectroscopy (SERS) of single molecules providing enhancement factor >106.1

Another method of preparation of metallic nanostructures is cathodic corrosion. This approach for platinum was studied by Koper group.3 We used this procedure for platinum ultramicroelectrode treatment. Obtained Pt NS exhibit unique catalytic properties towards electrooxidation of glucose.

References:

1. W. Nogala, P. Kannan, S. Gawinkowski, M. Jönsson-Niedziolka, M. Kominiak, J. Waluk and M. Opallo, Nanoscale, 7, 10767 (2015).

2. M. Michalak, A. Roguska, W. Nogala and M. Opallo, Nanoscale Advances, 1, 2645 (2019).

3. T. Hersbach, Alexei. Yanson and M. Koper, Nature Communications, 7, 12653 (2016).

Figure 1
(Invited) Morphology and Conductivity of Copper Hexacyanoferrate Films
Authors: Hosseini Pouya , Wolkersdörfer Konrad , Wark Michael , Redel Engelbert , Baumgart Helmut , Wittstock Gunther
Published: May 2020

Metal hexacyanometallates (MHCMs) form a large family of coordination network compounds [1]. They have variable and tunable physical and chemical properties due to the three-dimensional framework of alternating metal knots connected by a non-innocent small bridging ligand forming interconnected channels that can accommodate solvent molecules and counter ions. Therefore, these materials have been comprehensively studied in several different fields, including, functional materials for charge storage, electrocatalysis, electrochromic devices or light harvesting. For the mentioned applications, conductivity is critical, to which i) electronic conductivity by electrons or holes [2], ii) ionic conductivity by mobile alkali ions in the channels of the MHCMs [3], and iii) proton conductivity [4] may contribute. In larger scale for real application, the conductivity depends not only on intrinsic material properties but also on the morphology. Morphology (particularly grain boundaries) plays an important role in determining the pathway of charge carrier transport (electrons and holes) in the film. From first principles it is expected that continuous compact crystalline films will have better electrical conductivity.

Here, we present results on copper hexacyanoferrate which demonstrate particularly well the variation of film morphology and its influence on conductivity as a key functional property. We succeeded in devising a simple method for preparation of metal hexacyanoferrates as a thin continuous film by a combination of sonication-assisted casting and vapor-assisted conversion, without the need for surface pre-treatment. This is especially helpful for coating substrates composed of different materials. Films obtained in this way show conductivities higher than that of powder pellets with equivalent crystal structure. Temperature-dependent and humidity-dependent measurements on powder pellets revealed the activation energies for charge transport as well as the role of zeolitic water in facilitating the charge transfer.

1. Paolella, A.; Faure, C.; Timoshevskii, V.; Marras, S.; Bertoni, G.; Guerfi, A.; Vijh, A.; Armand, M.; Zaghib, K. A Review on Hexacyanoferrate-based Materials for Energy Storage and Smart Windows: Challenges and Perspectives. Mater. Chem. A
2017, 5, 18919–18932.

2. Behera, J. N.; D’Alessandro, D. M.; Soheilnia, N.; Long, J. R. Synthesis and Characterization of Ruthenium and Iron−Ruthenium Prussian Blue Analogues. Mater.
2009, 21, 1922–1926.

3. Ishizaki, M.; Ando, H.; Yamada, N.; Tsumoto, K.; Ono, K.; Sutoh, H.; Nakamura, T.; Nakao, Y.; Kurihara, M. Redox-Coupled Alkali-Metal Ion Transport Mechanism in Binder-Free Films of Prussian Blue Nanoparticles. Mater. Chem. A
2019, 7, 4777–4787.

4. Ohkoshi, S.-I.; Nakagawa, K.; Tomono, K.; Imoto, K.; Tsunobuchi, Y.; Tokoro, H. High Proton Conductivity in Prussian Blue Analogues and the Interference Effect by Magnetic Ordering. Am. Chem. Soc.
2010, 132, 6620–6621.
(Invited) Controlling Free Charge Density Gradients in Ionic Liquid Media
Authors: Blanchard Gary J.
Published: May 2020

Room Temperature Ionic Liquids (RTILs) have found use in a variety of practical applications, including chemical synthesis and supercapacitor development, but many fundamental issues remain to be resolved in understanding dynamics, organization and the response of these materials to external forces. We have demonstrated that RTILs in contact with a charged surface can exhibit a free charge density gradient (ρf
) that extends over ca. 100 μm. The existence of such a free charge density gradient in a fluid medium is without precedent and needs to be understood. Experimental and theoretical investigations of RTILs have revealed organization of some type over a variety of length scales, ranging from ca. 10 nm to ca. 100 μm. The term “organization” is not well-defined, however. The existence of any type of organization over such a range of length scales is highly unusual for a liquid, particularly so for a macroscopic free charge density gradient in an ionic liquid. Achieving a deeper understanding of this phenomenon is important because of its implications in how we conceptualize and use this class of materials.

We report on experiments that have elucidated the spatial extent of the induced gradient, it's magnitude, and the chemical and structural factors that serve to determine these factors. We also present a model for understanding this gradient that draws on known physical properties of materials such as piezoelectrics. The optical and physical behavior of RTILs draw analogy to piezoelectric properties in solids and the demonstration of this correspondence provides a novel framework for the interpretation of the unexpected phenomena we have reported.
Dimethylenebis-(tetra-decyldimethylammonium Bromide)-Driven Au Nanoparticles: Hg2+ Sensing a Competency
Authors: Kim Hohyeong , Jae-Young Park
Published: May 2020

Heavy metal ions can cause severe threats to the environment and human health, and the potential sources of substantial metal ions are mining, agriculture, toxic wastes, electronic merchandise, and natural discharge from earth’s crust into the surroundings. This discharge from oceanic and volcanic emissions end up in the contamination of underground water resources and human beings get exposed to the same. Among aforesaid ions, mercury ions are incredibly fatal and may cause serious health problems if consumed by individuals, leading to numerous critical diseases such as harmful effects on immune systems, cancer, organ damage, nervous system damage, etc.

In order to confirm these, it is essential to investigate the influence of the shorter hydrocarbon chain length on the detection performance of metal nanoparticles. In view of that, we selected dimethylenebis-(tetra-decyldimethylammonium bromide) (14–2-14) GS with a shorter hydrocarbon chain length and further investigated sensitivity and selectivity of anisotropic nanoparticles.
(Invited) Hybrid Porphyrin – Polyoxometalate Copolymer for Photo(electro)Chemical Applications: From Flat to Mesoporous ITO Electrodes
Authors: Ruhlmann Laurent , Liang Yiming , Wang Jingjing , Bonnefont Antoine
Published: May 2020

The development of hybrid polymers incorporating polyoxometalates (POMs) is a promising approach to elaborate new functional materials. To expand the practical applications, their association to a visible-light photosensitizer is needed. In this context, we have developed a method of electropolymerization of POMs based on nucleophilic attack onto the electrogenerated porphyrin dications.
1-2
The formation of hybrid POM-porphyrin copolymeric films (Fig. 1, film I) can be obtained by the electro-oxidation of porphyrin in the presence of the hybrid POM bearing two pyridyl groups (Py-POM-Py)
3
. This process is feasible for various type of POMs such as Dawson, Lindqvist or Keggin type POMs
4-6
. A second methodology is also proposed to form hybrid POM-porphyrin films (Fig. 1, films II or III): first the formation of cationic polyporphyrin electropolymer. Then, by metathesis reaction, the (partial) exchange onto the surface of the initial counter ions by the POMn- or by the nanoparticles stabilized with POMn- (POMn-@M, M = Ag, Au, Pt, etc.).
7
The photovoltaic performances of these hybrid materials have been investigated by photocurrent transient measurements under visible-light illumination
8-10
given by now good efficiency. In order to increase the efficiency, mesoporous ITO electrodes (nanofiber formed by electrospun or porous ITO electrode obtained using a colloidal co-assembly approach) have been used and will be discussed.

1. L. Ruhlmann, A. Schulz, A. Giraudeau, J.-H. Fuhrhop, J. Am. Chem. Soc., 1999, 121, 6664.

2. Z. Huo, J.-P. Gisselbrecht, R. Farha, M. Goldmann, E. Saint-Aman, C. Bucher, L. Ruhlmann, Electrochimica Acta, 2014, 122, 108.

3. D. Schaming, C. Allain, R. Farha, M. Goldmann, S. Lobstein, A. Giraudeau, B. Hasenknopf, L. Ruhlmann, Langmuir, 2010, 26, 5101.

4. I. Azcarate, I. Ahmed, R. Farha, M. Goldmann, X. Wang, H. Xu, B. Hasenknopf, E. Lacôte, L. Ruhlmann, Dalton Trans.
2013, 42, 12688.

5. Z. Huo, I. Azcarate, R. Farha, M.Goldmann, H. Xu, B. Hasenknopf, E. Lacôte, L. Ruhlmann, J. solid State Electrochemistry, 2015, 19, 2611.

6. Z. Huo,D. Zang,S. Yang,R. Farha,M. Goldmann,B. Hasenknopf, H. Xu, L. Ruhlmann, Electrochimica Acta, 2015, 179, 326.

7. Z. Huo,A. Bonnefont, C. Bucher, L Ruhlmann, Electrochimica Acta, 2018, 274, 177.

8. I. Ahmed, R. Farha, M. Goldmann, L. Ruhlmann, Chem. Comm.
2013, 49, 496.

9. I. Ahmed, R. Farha, Z. Huo, C. Allain, X. Wang, H. Xu, M. Goldmann, B. Hasenknopf, L. Ruhlmann, Electrochimica Acta, 2013, 110, 726.

10. I. Azcarate, Z. Huo, R. Farha, M. Goldmann,H. Xu, B. Hasenknopf, E. Lacôte, L. Ruhlmann, Chem. Eur. J.
2015, 21, 8271.

Figure 1
(Invited) Optimizing Iridium Utilization for Oxygen Evolution Reaction – Viability of the Supported Ir Oxide Nanoparticles Strategy
Authors: Claudel Fabien , Abbou Sofyane , Chattot Raphaël , Sola-Hernandez Lluis , Beauger Christian , Peron Jennifer , Maillard Frédéric , Dubau Laetitia
Published: May 2020

Determining the relationships between structure, oxidation state and oxygen evolution reaction (OER) activity is fundamental to design improved anode catalysts for polymer electrolyte membrane water electrolyser (PEMWE) devices. To date, Ir-based electrocatalysts are the best compromise between activity and stability. According to the scarcity of Ir on the Earth crust, the deployment of PEMWE technology cannot overlook an optimized utilization of Ir loading. Following the successful approach in proton-exchange membrane fuel cells (PEMFC) consisting of using carbon-supported Pt nanoparticles instead of Pt-blacks, we investigated supported Ir oxide nanoparticles. The nature of the support appears to be crucial since high-surface area carbon supports are rapidly degraded in the operating conditions of a PEMWE anode (E > 1.6 V vs. the reversible hydrogen electrode, T = 80 °C). We opted for alternative support materials based on doped tin oxide. In this contribution, a wide and sound library of Ir oxide materials differing from each other by the presence/absence of support and by the Ir architecture has been studied by identical location transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma mass spectrometry and electrochemical techniques (Figure 1). It allowed us to establish trends on the viability of supported Ir oxide catalysts in the harsh PEMWE operating conditions [1].

[1] F. Claudel, L. Dubau, G. Berthomé, L. Sola-Hernandez, C. Beauger, L. Piccolo, F. Maillard,

ACS catal.,
2019, 9 (5), 4688–4698.
Surface Engineering of Carbon Nanotubes with Inorganic-Organic Materials for Electrochemical Capacitors.
Authors: N'Diaye Jeanne , Siddiqui Shaheer , Lian Keryn
Published: May 2020

Composite electrodes comprised of inorganic-organic molecular materials are of great interest in applications such as electrochemical capacitors (ECs). ECs store and release charge via double layer capacitance (EDLC) or pseudocapacitance. The carbon materials used for EDLC has low capacitance, while pseudocapacitive materials such as redox active polymers or metal oxides have long term stability issues. Therefore, anchoring inorganic-organic materials on a carbon substrate can leverage the advantages of both EDLC and pseudocapacitance. Composite electrodes of kegging type polyoxometalates (POM) deposited on polydiallyldimethylammonium chloride (PDDA) via the layer-by-layer assembly has been well established and has shown great promise [1-3] . The issues are the limited operation window and the inert PDDA layer. Suitable alternatives that can complement the redox activity of POMs and enlarge the operating potential window are redox active polymers [4].

The objectives of this work are to: 1) develop and optimize an electroactive inorganic-organic composite electrode based on a carbon nanotube (CNT) substrate modified with polyluminol (CpLum) and H5GeMo11VO40.24H2O (GeMo11V); 2) study the electrochemical behavior of the composite electrode with and without PDDA for electrochemical capacitors; and 3) investigate the interactions between each layer.

GeMo11V was first deposited onto CNT using PDDA as an anchor. The vanadium atom in the kegging structure provided an additional electrochemical redox peak with improved capacitive behavior on the cyclic voltammogram (CV) as seen in figure 1. First, CpLum, and GeMo11V were applied on CNT (CNT-CpLum-GeMo11V), then co-deposited with PDDA (CNT-CpLum-PDDA-GeMo11V). For both composite electrodes, CpLum and GeMo11V contributed to the redox activity leading to a wider potential window. The CV of CNT-CpLum-GeMo11V showed more reversible redox peaks with a slightly reduced GeMo11V contribution compared to CNT-CpLum-PDDA-GeMo11V that had a smoother CV shape. The decrease in GeMo11V contribution was attributed to the smaller amount of positive charge within the CpLum chain needed to anchor the GeMo11V. Each layer had a distinct role in the inorganic-organic composite electrode. The CpLum polymer added additional redox activity in the higher potential range, while PDDA attracted and held the GeMo11V, which provided redox activity in the lower potential range. All three layers had a synergistic interaction and provided enhanced charge storage properties with good rate capability and cycling stability.

REFERENCES

1. M. Genovese, Y. W. Foong and K. Lian, Electrochimica Acta, 199, 261 (2016).

2. M. Genovese and K. Lian, Current Opinion in Solid State and Materials Science, 19, 126 (2015).

3. M. Genovese, Y. W. Foong and K. Lian, Journal of The Electrochemical Society, 162, A5041 (2015).

4. N. Casado, G. Hernández, H. Sardon and D. Mecerreyes, Progress in Polymer Science, 52, 107 (2016).

Figure 1
Neuronal Tau Protein Self-Assembly on Gold Surface: Electrochemical Impedance Spectroscopy and Cyclic Voltammetry Studies
Authors: Wallace William , Martic Sanela
Published: May 2020

Tau is a neuronal protein responsible for microtubule formation [1]. It is also the pathological protein active in the Alzheimer’s Disease (AD) pathway. When Tau begins to aggregate as a result of misfolding, the neuronal cells die due to the lack of microtubule formation and can take on prion-like properties [2]. Therefore, detection of aggregated Tau can serve as a powerful tool in the early diagnosis of AD and dementia related diseases. As has been previously demonstrated, Tau 441 can be detected with an electrochemical immunoassay based on the electrochemical impedance spectroscopy (EIS) by using gold electrode [3]. The EIS was also used to monitor interactions between Tau protein and Heparin [4]. Herein, we describe use of EIS and cyclic voltammetry (CV) to monitor and detect self-assembly of Tau protein on gold electrode. After modifying the surface of the electrode with Tau, the aggregation of Tau was performed using Heparin, as an aggregation inducer. The EIS and CV were measured as a function of Tau or Heparin concentrations, and incubation time and temperature. The control experiments included, Tau-free surface, Heparin-free solution, buffer solution in order to minimize aggregation. The charge transfer resistance, Rct, was determined by fitting the experimental data to the equivalent circuit. The Rct values for Tau-films on gold surface were compared prior and post aggregation. The Rct values were highly dependent on the experimental conditions used and that the electrochemical methods are promising sensing platforms for detection of neurodegenerative biomarkers which undergo self-assembly and aggregation.

References

[1] M.D. Weingarten, A.H. Lockwood, S. Hwo, M.W. Kirschner, A Protein Factor Essential for Microtubule Assembly, Natl. Acad Sci. 72 (1975) 1858–1862.

[2] F. Clavaguera, J. Hench, M. Goedert, M. Tolnay, Prion-like transmission and spreading of tau pathology, Neuropathol. Appl. Neurobiol. 41 (2015) 47–58.

[3] N. Carlin, S. Martic-Milne, Anti-tau antibodies based electrochemical sensor for detection of tau protein biomarkers, J. Electrochem. Soc. 165 (2018) G3018–G3025.

[4] H. Trzeciakiewicz, J. Esteves-Villanueva, R. Soudy, K. Kaur, S. Martic-Milne, Electrochemical characterization of protein adsorption onto YNGRT-Au and VLGXE-Au surfaces, Sensors (Switzerland). 15 (2015) 19429–19442.
Surface Design: Exploiting the Instability of Small Nanoparticles on Metallic Substrates
Authors: Awais Nashwa , Rodriguez Paramaconi , Albrecht Tim
Published: May 2020

Small metal nanoparticles (NPs) within the size range of 1-3 nm exhibit unique electronic and catalytic properties.1–3 Thiolated nanoparticles have been shown to undergo an entropically driven redistribution of the capping layer with a Ausurface-AuNP system. It has been postulated that different substrate and NP materials may be employed for surface design.4

The aim of this work was to investigate surface structure modification of different substrate-NP combinations, in alkaline media and via their performance in the electro-catalytic decomposition of glycerol (GlyOH).5 Ptsurface-AuNP and Ausurface-PtNP combinations were investigated, by immersion of the surfaces into solutions of the NPs. AuNPs were synthesised using a bottom-up metal reduction6, and PtNPs were synthesised via the cathodic corrosion method.7,8 Electrochemical responses were measured using cyclic voltammetry (CV).

Ptsurface-AuNP resulted in a lower current response, but no change in characteristic Pt peaks within the CV profile, indicating that the AuNPs remain protected by the thiol capping layer on the Pt surface. However, Ausurface-PtNP gave a CV displaying both Au and Pt characteristic peaks (Fig. 1), suggesting there is thiol surface diffusion from the PtNPs into the bulk.

1 S. Hrapovic, Y. Liu, K. B. Male and J. H. T. Luong, Anal. Chem., 2004, 76, 1083–1088.

2 R. Narayanan and M. A. El-Sayed, Nano Lett., 2004, 4, 1343–1348.

3 T. Albrecht, S. F. L. Mertens and J. Ulstrup, J. Am. Chem. Soc., 2007, 129, 9162–9167.

4 E. Pensa and T. Albrecht, J. Phys. Chem. Lett., 2018, 9, 57–62.

5 J. Monzó, Y. Malewski, F. J. Vidal-Iglesias, J. Solla-Gullon and P. Rodriguez, ChemElectroChem, 2015, 2, 958–962.

6 H. Qian and R. Jin, Chem. Mater., 2011, 23, 2209–2217.

7 A. I. Yanson, P. Rodriguez, N. Garcia-Araez, R. V Mom, F. D. Tichelaar and M. T. M. Koper, Angew. Chemie Int. Ed., 2011, 50, 6346–6350.

8 A. I. Yanson, P. V Antonov, P. Rodriguez and M. T. M. Koper, Electrochim. Acta, 2013, 112, 913–918.

Figure 1
Electrochemical Ammonia Recovery for Improving Efficiency of Food Waste Anaerobic Digestion
Authors: Wig Megan , Patricelli Colin , Chen Weikun , Stephan Aria , Kim Taeyoung
Published: May 2020

Anaerobic digestion is a biological process which is used to degrade organic material including food waste. Food waste anaerobic digestion (FWAD) is a sustainable way to reduce the waste going to landfills and produce methane which can displace fossil fuels. A major challenge of FWAD is that the microbes produce ammonia during the process, thus inhibiting microbial activities. Ammonia recovery can reduce microbial inhibition and improve the overall efficiency. The recovered ammonia can also be used as fertilizer. While the use of electrochemical approaches, such as electrodialysis (ED), can enable effective recovery of ammonia without the need for chemical input to elevate pH for stripping, it consumes high amounts of energy due to the cell voltage required for water electrolysis. A new electrochemical approach utilizing a redox (Fe(CN)6
3−/4−) was demonstrated here to minimize the energy consumption for ammonia recovery. To maintain a current density of 25 A/m2, the redox couple solution required 0.11 V, while the electrolysis under the same conditions required 2.17 V. With a 0.05 M redox couple solution and carbon paper, 50% of the NH4
+ was separated from a synthetic digestate (0.6 M NH4Cl) at a current density of 125 A m−2. Ammonia flux achieved (1300 g-N m−2 d−1) was 10 times higher than a previously reported value using ED with energy consumption (2.72 kWh kg-N−1) that was reduced to approximately a half. Additional experiments to further improve process efficiency were conducted using several carbon electrodes, including carbon paper, carbon cloth, and carbon felt, and the effect of surface treatment methods on electrochemical properties was evaluated using cyclic voltammetry. These results support the implementation of redox couples as an energy-efficient method for ammonia recovery during anaerobic digestions.
Theoretical Study of the Charge Transport Mechanism in a Sodium Selenide (Na2Se) Cathode for Sodium-Selenium Batteries
Authors: Park Sungwon , Paek Eunsu
Published: May 2020

Selenium (Se) is recognized as a promising cathode material for sodium-selenium (Na-Se) batteries because of its high electrical conductivity on the order of 10-3 S m-1 and facile sodiation kinetics. Although the terminal product, Na2Se, could limit the overall battery conductivity, fundamental understanding of the charge transport mechanism and the formation of final product remains largely unexplored. Based on density functional theory, we evaluate the influence of each type of defect and strain on conductivity in Na2Se by calculating the formation energy and mobility. We found that hole polaron (p+) can stably form on Se ion upon initial distortion. Our calculations also show that the negatively charged sodium vacancy (VNa
-) could be the major charge transport carrier with its lowest formation energy and fast mobility. While diffusion barrier of p+ is considerably smaller than that of VNa
-, the electronic transport related to p+ is suggested to be negligible due to its high formation energy. Once the vacancy-polaron (VNa
- ˗ p+) complex forms, the charge transport could be hindered mainly due to its charge neutrality and the relatively large binding strength of the complex. Lastly, we will also discuss the influence of compression which could be induced by significant volume change of Na-Se alloys on the conductivity of Na2Se.
Tuning Ion Diffusivity and High-Rate Cycling Performance Via Graphite Exfoliation for Rechargeable Aluminum-Graphite Batteries
Authors: Xu Jeffrey H. , Jadhav Ankur L. , Turney Damon E. , Messinger Robert J.
Published: May 2020

Rechargeable aluminum-graphite batteries using chloroaluminate-containing ionic liquid electrolytes store charge when chloroaluminate anions (e.g. AlCl4
-) intercalate into graphite1,2. Such batteries utilize electrodes that are globally abundant, low-cost, and safe, while exhibiting ultra-fast rate capabilities, high cycle life and discharge voltages of ca. 2 V. Recently, we elucidated the relationship between graphite structure and macroscopic electrochemical properties such as high-rate performance and the maximum intercalation composition.3 Variable-rate cyclic voltammetry (CV) revealed potential-dependent transport regimes that yield new insights into their ultra-fast rate capabilities. To directly observe the chloroaluminate species intercalated within the graphite electrodes, we performed solid-state 27Al MAS NMR measurements, which revealed their various local environments and populations. To aid the interpretation of the experimental results, DFT calculations were performed to compute the magnitude of 27Al NMR shift contributions due to varying graphite d-spacing, aromatic ring-current shielding, and quadrupolar interactions.

With this increased understanding of the elusive transport mechanism of sterically-bulky chloroaluminates, the current technological objective is to improve the high-rate capacity retention of synthetic graphite electrodes. To tune the ionic diffusivity within the graphite framework, we employed liquid-phase exfoliation and centrifugation to modify the c-axis thickness of the highly-ordered pristine graphites, generating few-layered graphene structures that we characterized using Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). In full-cell electrochemical tests of the exfoliated-graphite electrodes, variable-rate galvanostatic cycling revealed increased capacity retention (~75% @ current density of 960 mA/g, compared to ~43% for non-exfoliated synthetic graphite). Furthermore, galvanostatic intermittent titration technique (GITT) experiments revealed modified ionic diffusivity and ohmic resistances. These results are expected to aid the rational design of graphite electrodes for enhanced performance in aluminum-graphite batteries.

(1) Lin, M.-C.; Gong, M.; Lu, B.; Wu, Y.; Wang, D.-Y.; Guan, M.; Angell, M.; Chen, C.; Yang, J.; Hwang, B.-J.; Dai, H. An Ultrafast Rechargeable Aluminium-Ion Battery. Nature
2015, 520, 324–328.

(2) Sun, H.; Wang, W.; Yu, Z.; Yuan, Y.; Wang, S.; Jiao, S. A New Aluminium-Ion Battery with High Voltage, High Safety and Low Cost. Chem. Commun.
2015, 51, 11892–11895.

(3) Xu, J. H.; Turney, D. E.; Jadhav, A. L.; Messinger, R. J. Effects of Graphite Structure and Ion Transport on the Electrochemical Properties of Rechargeable Aluminum-Graphite Batteries. ACS Appl. Energy Mater.
2019, 2, 7799–7810.
Synthesis of Carboxylated Viologen Cations and Their CT Salts with 1,3-Bis(dicyanomethylidene)Indan Anion
Authors: Yamaguchi Hiroto , Saito Erika , Uno Koya , Yamakado Ryohei , Okada Shuji , Yoshida Tsukasa
Published: May 2020

Charge transfer (CT) salt by combination of ionic organic donor and acceptor can be an interesting alternative to eliminate large voltage loss in bulk-heterojunction organic solar cells. We have succeeded in synthesis of novel CT co-crystals of 1,3 bis(dicyanomethylidene)indane anion (TCNIH-) donor and N-alkyl substituted viologen cations acceptor to exhibit broad and intense light absorption from visible to NIR. However, it is not straightforward to employ heavily crystallizing organic salts in thin film devices. As an alternative approach to prove the concept, here we propose attachment of the CT pair as a dye to porous oxide semiconductor to dissociate its CT exciton and to harvest it as current in a dye sensitized solar cell (DSSC) fashion. In this work, carboxylated viologen derivatives, N,N’-bis(carboxymethyl)-4,4’-bipyridinium chloride (CE2V) and N-(2-carboxymethyl)N’-methyl-4,4’-bipyridinium iodide (CEMV) (Fig. 1) were synthesized for their attachment to porous ZnO. Their formation of CT salts with TCNIH- has also been studied.

CE2V was synthesized by carboxylation of 4,4’-bipyridinium with acrylic acid and subsequently converted to chloride with hydrochloric acid. CEMV iodide was prepared by monomethylating 4,4’-bipyridinium with methyl iodide and carboxylation with acrylic acid. The synthesized viologen was mixed with TCNIH- in 1 : 2 ratio in water, filtrated and recrystallized in ethanol to identify the structure of the co-crystals. Mesoporous ZnO film prepared by doctor blading was sequentially soaked in ethanolic solution of CE2V or CEMV, and acetone/toluene solution of TCNIH-, to obtain ZnO/viologen/TCNIH hybrid structure in the end. The attachment of respective molecules was checked by UV-vis absorption both for the film samples and the ammonia solution dissolving the entire film.

Formation of CT salts was confirmed by significant broadening of the absorption towards NIR as compared to that of the Na+ salt of TCNIH- (Fig. 1), so that the presence of the carboxylic acid anchor group in viologens do not disturb their intimate ionic interaction with TCNIH-. Triclinic single crystalline structure of the co-crystals was identified by XRD. CE2V and CEMV were adsorbed at high concentrations (500 μM and 500 μM, respectively) onto ZnO, so that the carboxylic acid group indeed acted as an anchor for their attachment to ZnO. The anionic TCNIH- in fact could directly be adsorbed onto ZnO to yield bluish films, whose spectrum, however, differed from those with pre-attached viologens (Fig. 1). Those of ZnO/viologen/TCNIH indicate clear broadening towards red, which can be attributed to the formation of CT pairs. Photoelectrochemical analysis in the presence of suitable redox system is expected to result in photocurrent from the CT state.

Figure 1
Synthesis of Poly-Neutral Red and Its Electrocatalytic Property Towards CO2 Reduction Reaction
Authors: Huang Xin , Harada Yuya , Nishiumi Nobuyuki , Coskun Halime , Aljabour Aziz , Stadler Philipp , Yoshida Tsukasa
Published: May 2020

Concentration of carbon dioxide (CO2) in the atmosphere has steadily increased since industrial revolution. Despite the recent significant cost reduction of renewable electricity by solar and wind, their intermittency hinders the total shift to renewable energy. It is urgently needed to develop technologies for fast conversion of electrical energy into storable chemical energy by electrolysis, e.g., by water splitting and CO2 reduction. Stable and high-performance electrocatalysts are essential but must be developed without depending on precious metals for the real use and sustainability of the technology.

Recently, we have demonstrated high and stable electrocatalytic properties of conductive organic polymers, such as polydopamine (PDA) and polyguanine (PGA) for hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR)1,2). Hydrogen bonding N and O atoms introduced to these polymers are expected to stabilize the reaction intermediates for their high catalytic activities. In this study, a phenazine dye, neutral red (NR) was employed as the monomer to obtain a metal-free catalyst. NR bears many amino functions to make it electropolymerizable just like poly-aniline (electropolymerization deposition, to be called EPD). Also, oxidative chemical vapor deposition (oCVD) was employed to obtain PNR. Synthesis, characterization and comparison of the catalytic activities of PNR by EPD and oCVD are discussed.

EPD of PNR onto carbon felt (CF) was carried out by cycling potential between -1 and +1 V vs. Ag/AgCl for 100 cycles in an aqueous solution containing 0.2 mmol/L NR and 0.5 mol/L KNO3 (pH 5) at 50 mV/s. oCVD of PNR was performed in a three-zone quartz tube furnace under N2 flow, while setting the temperature for NR, sulfuric acid and CF at 375, 220 and 100ºC, respectively, for 240 min. PNR-modified as well as bare CF electrodes were measured under N2 and CO2 in a 1 M KNO3 (pH 7) for their catalytic activities for HER and CO2RR.

While bare carbon felt (CF) electrode does not show any catalytic activity towards CO2RR, showing about -3 mA cm-2 current at –1 V vs. Ag/AgCl, supposedly dominated by that for HER, the PNR coated CFs show enhanced current (Fig. 1a). That by EPD gives about -5 and -6 mA under N2 and CO2, respectively, indicating its moderate catalytic activity for HER and CO2RR. PNR prepared by oCVD, on the other hand, gives -6 and -12 mA, to demonstrate its superior activity, especially for CO2RR. Chronoamperogram measured during long term electrolysis for 17 h at the oCVD PNR electrode indicates reasonable stability of the catalysis (Fig 1b). These results already nicely confirm catalytic activity of PNR for its conductivity and hydrogen-bonding ability.

References:

1. H. Coskun et al., Sci. Adv., 2017, 3, e1700686.

2. H. Coskun et al., Adv. Mater. Interf., 2019, 10, 1901364.

Figure 1
Carbon Fiber Microelectrodes Modified with Polymers for Enhanced Neurochemical Detection of Dopamine and Metabolites
Authors: Wonnenberg Pauline M , Zestos Alexander George
Published: May 2020

While different electrochemical sensors have been introduced over the past thirty years, carbon-fiber microelectrodes (CFMEs) are considered to be the standard electrodes for neurotransmitter detection. Fast-scan cyclic voltammetry (FSCV), an electroanalytical method, primarily uses CFMEs and has the ability to follow neurochemical dynamics in real time. In conjunction with FSCV, CFMEs have the capability to accurately measure the oxidation of several crucial neurotransmitters, like dopamine, to produce specific cyclic voltammograms. Improvements in neurochemical detection with CFMEs were previously made through the coating of polymers onto the surface of the carbon-fiber. Polymers such as PEI, PEDOT, and Nafion were electrodeposited onto the surface of the electrodes to enhance neurochemical detection. This work demonstrates applications for enhancements in co-detection of similarly structured neurochemicals such as dopamine, DOPAL, 3-methoxytyramine, DOPAC, and other neurotransmitters. Manipulating the charge and surface structure of the carbon electrode allows for the improvement of sensitivity and selectivity of neurotransmitter detection. The analytes are detected and differentiated by the shape and the peak positions of their respective cyclic voltammograms. In addition, ex-vivo measurements and qualification of several neurotransmitters in zebrafish brain models are shown.
High-Performance Li-Se Batteries Enabled Via All-in-One Designed Cathode
Authors: Kim Soochan , Cho Misuk , Lee Youngkwan
Published: May 2020

As an alternative to Li-S battery, a Li-Se battery is promising due to its high volumetric energy density. However, practical applications have been limited by complex fabrication and undesirable electrochemical process during charge-discharge which leads to poor cycling performance and low rate capability. To overcome these obstacles, we demonstrate a new design of “all-in-one” Se cathode, which is a one-piece body combined with a cathode and a solid polymer electrolyte. It is simply prepared by electrodeposition of Se on Ni-foam and subsequent coating of the solid polymer electrolyte without using any binders or conductive additives. All-in-one Se cathode can provide facile manufacturing process, prohibit undesirable electrochemical reaction, enhance ion pathway, and secure safety from advantages of solid polymer electrolyte. Li-Se batteries assembled with all-in-one Se cathode and Li-metal anode exhibited highly stable performance with a low capacity decay of 0.003% per cycle at 1 C over 3000 cycles.
Phosphoric Acid Doping Levels in PBI-Based Membranes for the Application in High Temperature Fuel Cells: A Comprehensive Evaluation of Different Measurement Techniques
Authors: Arslan Funda , Böhm Thomas , Kerres Jochen A. , Thiele Simon
Published: May 2020

Alternative energy studies are crucial since the energy demand in the world increases rapidly. Nowadays, due to limited reserves of fossil fuel and CO2 emission, environmentally green energy is the most promising and desirable energy source for the future. In this context, fuel cells becoming one of the most promising alternative energy conversion devices. Especially polymer electrolyte membrane fuel cells (PEMFCs) are of great research interest.

Theoverall efficiency of PEMFCs is strongly influenced by the polymer membrane placed between the anode and cathode. The current state-of-the-art perfluorosulfonic acid (PFSA)-based membranes used in PEMFCs, such as Nafion, rely on the presence of water as the charge carrier for an efficient proton conductivity, and operate usually only up to 80 °C. Therefore, Nafion-based systems require water management, which can be avoided by using polybenzimidazole (PBI)-based membranes instead; operating at higher temperatures (up to 180 °C). Nevertheless, pristine PBI-based membranes need to be doped with acid in order to produce a highly proton conductive system. In this context, phosphoric acid (PA) is the most promising acid as the proton conduction medium. PA doping levels are essential as they govern conductivity, while an excess acid doping can deteriorate mechanical and thermal properties of the membrane. Therefore, the optimization and determination of the doping levels are important for high temperature polymer electrolyte membrane fuel cells. Commonly, titration or weighing of the membranes are used for the determination of the acid doping level, but they suffer from low accuracy and precision.

In this work, the acid doping level (ADL) of PBI-based membranes was studied by Raman, impedance, and energy-dispersive X-ray (EDX) spectroscopy, gravimetric and thermogravimetric analysis, and titration. The use of Raman spectroscopy is of great interest due to its non-destructive nature. It can be performed on the sample prior or post application in a HT-PEMFC. This study presents a new measurement protocol for ADLs by using Raman spectroscopy, which is a helpful tool for choosing the optimal ADL for a PBI-based membrane. Thus, the manufacturing process of high temperature fuel cells and their overall efficiency can be optimized.

Keywords: Acid Doping Level (ADL), Fuel Cells (FCs), High Temperature (HT), Polymer Electrolyte Membrane (PEM), Phosphoric Acid (PA), Polybenzimidazole (PBI)
Characterization of Europium Doped Silicon Oxide, Silicon Oxynitride, and Silicon Nitride Films Prepared By Integrated Ecr-PECVD and Magnetron Sputtering
Authors: Azmi Fahmida , Gao Yuxuan , Khatami Zahra , Mascher Peter
Published: May 2020

The compatibility of Si-based light sources with mainstream metal-oxide semiconductor technology has become very interesting over the past decades due to their potential in integrated optoelectronics circuits of monolithic Si [1]. A very promising approach to improve the light emission from silicon-based materials is doping silicon with rare earth elements, and numerous research is involved in this field [1]. However, there are only a few works on europium (Eu) doped silicon-based matrix. In this work, Eu doped silicon oxide, silicon oxynitride, and silicon nitride thin films were deposited on P (100) Si substrates using integrated electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) and magnetron sputtering. Silane (SiH4), oxygen (O2), and Nitrogen(N2) gases were used as precursors and solid Eu as the sputtering target. The integrated ECR-PECVD and sputtering system allows tunable and highly consistent Eu doping concentration, better control of the layer stoichiometry along with less hydrogen incorporation in the deposited film compared to conventional CVD systems [2]. Several thin films were investigated using room temperature photoluminescence (PL) and X-ray diffraction (XRD). A detailed investigation of the effect of annealing on the PL was performed. The annealing temperature was varied from 500 OC to 1200 OC in nitrogen and a mixture of nitrogen and hydrogen atmospheres. It was observed that the intensity of the PL spectra increased with increasing annealing temperature. Besides, the hydrogen passivation effect has been studied in this work, which shows that hydrogen passivation increases the intensity of the peak. Based on the XRD measurements, we have found that the amorphous silicon oxide structure changes to a crystalline structure by adding nitrogen in the film. Interestingly silicon oxynitride and silicon nitride films do not show any luminescence at room temperature. The influence of the precursors' gases in the atomic percentage of the thin films was analyzed by Rutherford Backscattering spectrometry (RBS). In addition to it, the thickness and the index of refraction were characterized by variable angle spectroscopic ellipsometry (VASE).

Reference:

1. Lin, Z., Huang, R., Wang, H., Wang, Y., Zhang, Y., Guo, Y., ... & Li, H. (2017). Dense nanosized europium silicate clusters induced light emission enhancement in Eu-doped silicon oxycarbide films. Journal of Alloys and Compounds, 694, 946-951.

2. Miller, J. W., Khatami, Z., Wojcik, J., Bradley, J. D. B., & Mascher, P. (2018). Integrated ECR-PECVD and magnetron sputtering system for rare-earth-doped Si-based materials. Surface and Coatings Technology, 336, 99-105.
Optoelectronic Properties of Ce3+ Doped Silicon Oxide and Oxynitride Electroluminescent Devices
Authors: Gao Yuxuan , Abdelal Aysegul , Azmi Fahmida , Khatami Zahra , Mascher Peter
Published: May 2020

In this work, we propose a new type of silicon-based electroluminescent device. The thin film emitting layers of the device were deposited using Electron-Cyclotron-Resonance Plasma Enhanced Chemical-Vapor Deposition (ECR-PECVD) with in-situ Ce3+ doping on a P-type silicon substrate. Oxygen was gradually substituted by nitrogen to produce silicon oxynitride thin films with different layer compositions. Refractive indices extracted from variable-angle spectroscopic ellipsometry (VASE) measurements classified the thin films into two main groups, silicon oxide (SiOx) and silicon oxynitride (SiOxNy). The thin film composition was studied by Rutherford Backscattering Spectrometry (RBS), verifying the gradual increase in oxygen content. Photoluminescence (PL) spectroscopy of the emitting layer was obtained using a 375 nm laser as an excitation source. All samples were subjected to the post-deposition annealing treatment for 1 hour at different temperatures varying from 600 to 1200°C in 95% N2 and 5% H2 ambient gas environment, yielding considerably stronger blue PL emission than as-deposited ones. PL intensity of SiOx showed a sudden increase due to the formation of Ce2Si2O7 clusters when annealed at 1200°C. Internal Quantum Efficiency (IQE) and External Quantum Efficiency (EQE) were measured using an integrating sphere and a UV-Vis-NIR spectrometer. The optimum layer composition and annealing condition to produce SiOxNy thin films with maximized Ce3+ excitation efficiency were obtained. To further investigate the electrical performance of the produced samples, the thin films were coated with indium tin oxide (ITO) and aluminum (Al) on the top and bottom side of the thin film respectively. Current-Voltage (I-V) measurements showed improved charge injections in SiOxNy compared to SiOx, due to the reduction of the bandgap upon the incorporation of nitrogen.