bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Electroreduction of CO2 (CO2RR) on Pyrolysed Transition Metal Porphyrins
Authors: Kao Yi-Lin , Paul Stephen , Herrmann-Geppert Iris , Kramm Ulrike Ingrid , Bogdanoff Peter 
Published: May 2020

Pyrolysed transition metal porphyrins (MeNxC) were originally developed as alternative catalysts for the electrochemical reduction of oxygen (ORR). The catalytic centers were identified as base transition metal ions, integrated into graphene layers of a carbon matrix via nitrogen atoms. The carbon serves as a conductive support and influences the entire catalytic process with its variable electronic and chemical properties. Thus, this class of materials can be classified as hybrid-material between inorganic and molecular catalysts.
Meanwhile it is known that this type of catalysts are also active towards the CO2RR. Our presentation will show results of electrochemical studies on pyrolysed transition metal porphyrins (MeNxC) as catalysts for the CO2RR under variation of the metal ions (Me: Fe, Co, Ni, Sn, Zn, Cu , Mn). Their activities are determined in gas diffusion electrode (GDE) configuration using CO2, CO or Ar gas feeds. The product composition of the gas phase at the outlet of the cell is analyzed simultaneously by mass spectroscopy. Soluble products are analysed via ion-chromatography. It is shown that the product composition of CO2RR, as well as the respective onset potentials, partial current densities, formation rates, and Faraday efficiencies vary strongly with the type of metal ions investigated in the catalytic center. Fe-, Co- and Ni-based catalysts form predominantly CO and suppress the competing hydrogen evolution reaction. CO-formation rates of 4 mmol/(hcm2)at -2V NHE and 200 mA/cm2 (Faraday efficiency close to 100%) were achieved on not yet optimized GDEs. The formation of significant amounts of hydrocarbons from CO2 was observed only on the Cu- based material. The analysis of the potential dependence during product formation under different gases fed to the GDE allows initial conclusions about the underlying mechanisms of the CO2RR.

Figure 1
Protein Assisted Fabrication of Metallic Nanorings and Spherical Nanoparticles for Electrocatalytic and Organocatalytic Applications
Authors: Pan Yani , Mauzeroll Janine 
Published: May 2020

Inspiration from nature has driven the development and application of greener nanomaterials prepared using biotemplates in the field of nanoscience. Compared to traditional chemical routes, bioinspired nanomaterial synthesis has the advantage of mild synthetic conditions such as aqueous environment, ambient temperature, and no requirement for organic capping agent. In addition, the structures of some biomolecules make it possible to fabricate nanomaterials with complex and interesting morphology that are difficult to achieve through chemical methods. In this study, tobacco mosaic virus coat protein (TMV cp) was investigated as a versatile template to mediate the synthesis of nanorings and spherical nanoparticles under neutral and alkaline conditions, respectively. While the prepared silver nanorings displayed superior selectivity (95% Faradaic Efficiency) and stability of catalyzing CO2 electroreduction (CO2 RR) compared to free silver nanoparticles prepared by chemical methods, the platinum nanorings showed excellent electrocatalytic activity for hydrogen evolution reaction (HER). Spherical nanoparticles synthesized under alkaline conditions (Pt, Pd and Au NPs) were also investigated for their catalytic behavior towards organic transformations such as 4-nitrophenol reduction and alkyne hydrogenation.
References:
[1] Huang J. et al. Chem. Soc. Rev., 2015, 44, 6330.
[2] Pan Y. et al. Nanoscale, 2019, 11, 1895.
[3] Kim C. et al. J. Am. Chem. Soc., 2015, 137, 13844.

Figure 1
Double Approach Towards 3D Electrodeposited RuOx Porous Structure for High Energy/High Power Micro-Supercapacitors
Authors: Benali Karroubi Lotfi , Patnaik Sai Gourang , Tran Chau Cam Hoang , Guay Daniel , Pech David 
Published: May 2020

Hydrous RuOx has been one of the well-studied materials for application in supercapacitors owing to its excellent properties (high conductivity similar to metals, redox activity capable of fast faradaic reactions and structural water enabling swift proton transfer and decreased diffusion distance). The main issue regarding supercapacitors is that, they suffer from low energy density compared to batteries. One way to overcome this problem is to increase surface area of the active material and hence the energy stored through 3D structuration of current collector. Multiple techniques have been used in this regard like 3D printing, pholitography methods...etc. However, these techniques are pretty complex, time consuming and have constraining conditions. Hence, it’s necessary to develop economic and simple routes for 3D structuration of electrodes for micro-supercapacitors. One simple, time efficient and easy to set up method that can be used under ambient conditions is the electrochemical structuration using dynamic hydrogen bubble template (DHBT). With this strategy, 3D scaffolds which can hold small quantities of intrinsic pseudocapacitve materials like RuOx can be fabricated. The challenge in this latter case is magnified, needing controlled decoration of active materials for efficient utilization and full benefit of the 3D framework. Hence, the pursuit of superior micro-supercapacitors not only needs controlled deposition, but also requires stable 3D scaffolds to maximize capacitance per footprint area1. We have previously shown electrodeposition of active RuOx on porous gold electrodes for micro-supercapacitors achieving a capacitance of 3 F/cm².2

One other approach would be to deposit the active material directly by the DHBT method. As RuOx is a good conductor this would not hinder its efficiency (this would not be the case for MnO2 for example). The difficulty here is that, not all metals can be deposited by the DHBT technique as other factors play a crucial role such as the exchanged current density towards H2 evolution and mechanical stability3.
In the current work, we report two different strategies for the 3D deposition of RuOx. The first is the successful fabrication of highly porous 3D platinum current collector using DHBT followed by a conformal coating of hydrous RuOx to achieve a specific capacitance as high as 7 F/cm². The second is the direct electrodeposition of the active material, RuOx, in a 3D porous structure. These two approaches are characterized and discussed within the framework of fabricating superior micro-supercapacitors with excellent capacitance and low internal resistance.

References

1. N. A. Kyeremateng, T. Brousse, and D. Pech, Nat. Nanotechnol., 12, 7–15 (2017)
2. A. Ferris, S. Garbarino, D. Guay, and D. Pech, Adv. Mater., 27, 6625–6629 (2015)
3. Plowman, B. J., Jones, L. A., & Bhargava, S. K. Chem. Commun., 51, 4331–4346 (2015)

Figure 1
Solar Desalination Using Dye-Sensitized Photoanode in a Redox Flow Desalination Cell
Authors: Mohandass Gowri , Trivedi Dhara , Kim Taeyoung , Krishnan Sitaraman 
Published: May 2020

Water desalination is a promising technological solution for assuring water security in many parts of the world. Although conventional desalination techniques, such as thermal desalination, reverse osmosis (RO), and electrodialysis (ED), are currently in use for supplying freshwater, it may not be a sustainable solution in the long term due to the heavy reliance on fossil fuels to power the process. The desalination driven by sunlight could be a potential, energy-conserving alternative to the existing techniques. Here, we demonstrated the use of redox-active photoanode to power the water desalination. We have used a dye-sensitized photoanode (of the Grätzel cell) as one of the electrodes of a water desalination cell, in which a redox couple (I−/I3
−) mediates light-to-energy conversion and sustains ion transport and ion separation in the cell. The cell consisted of electrode channels recirculating the redox couple and feed channels fed with 50 mM NaCl, which were divided by an alternative array of anion and cation exchange membranes. The short-circuit current (J
sc) achieved in the integrated solar desalination cell was 2.75 mA/cm2 using a Xenon lamp (100 mW/m2), which was significantly higher than previously reported DSSC-based solar desalination (J
sc = ~ 0.1 mA/cm2 [1]). This improved current density allowed for a reduction in NaCl concentration from 50 mM in the feed to 38 mM in the effluent, indicating that integrating photon-to-electron conversion and water desalination processes within a single device is a viable approach for solar-powered water desalination.
[1] Chen et al., Exploration of a photo-redox desalination generator, J. Mater. Chem. A, 2019, 7, 20169
Unraveling the Temperature Mediated Dual Band Edge in TiO2 Nanotubes with Improved Photocatalytic Property
Authors: Bhowmick Sangita , Saini Chetan , Gupta Mukul , Singhal Rahul , Sen Raja , Kanjilal Aloke 
Published: May 2020

The resurgence of photocatalytic activity of TiO2 is driven in past few decades owing to its potential to meet several contemporary global challenges, such as pollutant degradation, nonfossil fuel production from CO2, or H2 generation from aqueous solutions [1]. Among three TiO2 polymorphs anatase TiO2 (A-TiO2), rutile TiO2 (R-TiO2) and brookite TiO2, first two are the mostly investigated phases for photocatalytic application. However, the use of TiO2 photoelectrodes is limited owing to the recombination of photo-generated (e-h) pairs in the bulk, and also at the electrode/electrolyte interface. The overall efficiency associated with A-TiO2 is still considered to be higher with respect to R-TiO2 due to higher charge carrier mobility and slower charge recombination kinetics [2].Nevertheless, proper ratio of anatase-rutile phases (Degussa P25) is superior in photocatalytic activity than that of pure rutile or anatase phase. On the other hand, anodic TiO2 nanotubes TNTs have attracted wide interest due to their high surface-to-volume ratio with preferential electron transport towards the Ti back-contact, and a scalable synthesis by electrochemical anodization [3]. However, thermal annealing is needed to obtain anatase and rutile phases, besides achieving suitable ratio of mixed-phases for relatively high photocatalytic performance through efficient inter-granular charge transfer and minimizing the recombination processes. Temperature induced changes in surface morphology, grain size, crystal structure and composition also have significant influence on the photo-electrochemical properties of TNTs. Here, we report the synthesis of TNTs, and the correlation of optical band gap with structural transformation from anatase to rutile through intermediate mixed phases as a function of temperature and their corresponding effect on photocatalysis application. This is confirmed by means of UV-Vis spectroscopy, X-ray diffraction (XRD) and Raman Spectroscopy. X-ray Photoelectron Spectroscopy (XPS) analyses has also been carried out to understand the change in chemical behavior with annealing temperature, gives a clear evidence of sub-stoichiometric to stoichiometric TiO2 (Ti4+) phase transformation with increasing temperature via removal of the fluorine (F) species from the NT surface which eventually changes the crystallinity of the samples as observed in XRD patterns. Further, to comprehend the change in the local coordination environment of the constituent atoms in TiO2 nanotubes with annealing temperature, the samples have been characterized by X-ray Absorption Spectroscopy (XAS). Density functional theory (DFT) has also been employed to understand the underlying mechanism.

References

1. P.Roy et al., Angew. Chem., 50,13,(2011)
2. Yalavarthi, R., et al., Catalysts, 9,2,(2019)
3. J.M.Macak et al., Small, 3,2,(2007)
Electrochemical Reactivity of Flavonoids and Flavonoid-Metal Ion Complexes with the Superoxide Anion Radical
Authors: Lewis Tyra , Martic Sanela 
Published: May 2020

Reactive oxygen species (ROS), such as the superoxide anion radical, O2ׄ-, are by-products of aerobic cellular metabolism.1,2 ROS may serve as signaling molecules in some cellular processes, depending on the balance of ROS produced and ROS scavenging mechanisms at work.1 However, they may also lead to undesirable reactions in biological systems.1 Specifically, an excess production of ROS can cause oxidative stress, contributing to cellular death and the development of some pathological diseases, like cancer and Parkinson’s disease.1-3

Dietary flavonoids serve as antioxidant supplements to fight against ROS-induced damages in the system.4 Flavonoids are also known to play a role as metal ion chelators, in a biological environment, which subsequently modulates the antioxidant capacity of the flavonoid compound.1,4 Hence, greater understanding of flavonoid chemistry with ROS in the context of metal ions is needed.
In this work, a previously established three-electrode electrochemical assay was used to evaluate the reactivities of flavonoids and flavonoid-metal ion complexes with electrochemically-generated superoxide anion radical, O2ׄ-.5 Cyclic voltammetry (CV) was used with a glassy carbon working electrode, a Pt wire counter electrode and Ag/AgNO3 reference electrode immersed in DMF, in this assay. CV was used to measure the electrochemical signal associated with O2ׄ- and its modulation in the presence of a specific flavonoid and metal ion (Cu(II), Zn(II), Fe(III), Mn(II), Cd(II)). Data indicated that flavonoids depleted a signal associated with O2ׄ- and that this reactivity was regulated in the presence of metal ions.

References

1 P. Sharma, A. B. Jha, R. S. Dubey, and M. Pessarakli, J. Bot., 2012, 1–26 (2012).

2 M. P. Murphy, Biochem. J., 417, 1–13 (2008).

3 C. L. Bourvellec, D. Hauchard, A. Darchen, J.-L. Burgot, and M.-L. Abasq, Talanta, 75, 1098–1103 (2008).

4 K. E. Heim, A. R. Tagliaferro, and D. J. Bobilya, J. Nutr. Biochem., 13, 572–584 (2002).

5 N. L. Zabik, S. Anwar, I. Ziu, and S. Martic-Milne, Electrochim. Acta, 296, 174–180 (2019).
Investigating the Mechanical Properties of Na Metal for Solid-State Batteries
Authors: Chang Jiun-Yeu , Wang Michael , Sakamoto Jeff 
Published: May 2020

In recent years, increasing power density and reducing cost has fueled interest in developing all solid-state batteries. Na metal anodes have garnered attention because of its abundance and high theoretical capacity (1165 mA h g–1) [1]. However, similar to solid-state Li-ion conductors, it has been reported that dendrite growth through Na-ion conductors also occurs. It has been hypothesized that dendrite propagation through the electrolyte is dependent upon the elastic and plastic properties of the alkali metal anode [2]. Therefore, a better understanding of the mechanical properties of bulk Na can promote the further development of Na-based solid-state batteries.
In this study, several analyses were performed to gain insight into the mechanical properties of Na metal. Tensile and compressive tests were performed by using a load frame contained in an inert atmosphere. From the resulting stress-strain graphs, the yield strength was determined to be 0.283 MPa. An acoustic technique was employed to determine that the elastic modulus of Na was 4.6 GPa. Because Na has a relatively low melting point (98°C), the deformation mechanism of Na during battery operation is likely dominated by creep. To investigate the creep behavior of Na, tension creep measurements were performed. The creep exponent of Na was determined to be n = 7.4. Lastly, to better understand the mechanical behavior of Na at the various interfaces in a solid-state battery, compression tests were performed on varying substrates. Three interfaces were examined: Oil/Na (simulating a frictionless interface), current collector/Na, and Na/Na-β’’-alumina.
We believe the mechanical measurements in this work will provide new insights into in the design requirements for solid-state batteries utilizing Na metal anodes.
REFERENCE
1. Sun, B., Li, P., Zhang, J., Wang, D., Munroe, P., Wang, C., ... & Wang, G. (2018). Dendrite‐Free Sodium‐Metal Anodes for High‐Energy Sodium‐Metal Batteries. Advanced Materials, 30(29), 1801334.
2. LePage, W. S., Chen, Y., Kazyak, E., Chen, K. H., Sanchez, A. J., Poli, A., ... & Dasgupta, N. P. (2019). Lithium Mechanics: Roles of Strain Rate and Temperature and Implications for Lithium Metal Batteries. Journal of The Electrochemical Society, 166(2), A89-A97.
Evaluation of Porous Ni(Zn) Materials As 3D Matrices for Li Metal Electrodes
Authors: Fatahine Mohamed , Guay Daniel , Roué Lionel 
Published: May 2020

Due to its very high theoretical capacity (3861 mAh g-1 or 2062 mAh cm-3) and low redox potential (-3.04 V vs standard hydrogen electrode), lithium metal is one of the most attractive anode materials for batteries. However, its use in rechargeable batteries such as Li-S and Li-air batteries is problematic due to the uncontrolled formation of lithium dendrites during charge/discharge cycling, which can induce cell short circuit, aggravated adverse reactions, dead Li formation, polarization increase and large volume changes, resulting in safety concerns and low coulombic efficiencies. Various strategies have been evaluated to prevent the growth of Li dendrites such as: (i) electrolyte engineering for modifying the physicochemical properties of the solid electrolyte interphase and better regulating the current distribution during Li deposition; (ii) interface engineering by covering the Li surface with a protective coating before cycling; (iii) use of solid electrolyte or reinforced separator to mechanically block Li dendrite propagation and (iv) development of 3D substrates inducing a more uniform Li-ion flux in addition to act as stable hosts that guide Li plating and minimize the electrode volume variation upon cycling [1-3].
According to this latter strategy, the present study is focused on porous Ni and Ni-Zn electrodes elaborated by the dynamic hydrogen bubble template (DHBT) method [4]. The Li wettability of these electrodes as a function of their porosity and composition will be presented. Their ability to better control lithium dendritic growth will be discussed on the basis of cycling experiments in Li/S batteries, electrochemical dilatometry experiments and operando optical microscopy analyses.

References

[
1
] X.B. Cheng, R. Zhang, C.Z. Zhao, Q. Zhang, Toward safe lithium metal anode in rechargeable batteries: a review, Chem. Rev 117 (2017) 10403-10473.

[
2
]X.B. Cheng, J.Q. Huang, Q. Zhang, Review-Li metal anode in working lithium-sulfur batteries, J. Electrochem. Soc. 165 (2018) A6058-A6071.

[
3
] D. Lin, Y. Liu, Y. Cui, Reviving the lithium metal anode for high-energy batteries, Nat. Nanotechnol. 12 (2017) 194-206.

[
4
] M. Hao, V. Charbonneau, N. N. Fomena, J. Gaudet, D. R. Bruce, S. Garbarino, D. A. Harrington, D. Guay, . Hydrogen Bubble Templating of Fractal Ni Catalysts for Water Oxidation in Alkaline Media. ACS Appl. Energy Mater. 2 (2019) 5734-5743.
Electroactive Molecularly Imprinted Polymer for Selective Detection of 4-Nitrophenol
Authors: Ren Tianyu , Si Bo , Chen Yuan , Halpern Jeffrey M , Seitz William Rudolf 
Published: May 2020

We propose to develop a reusable electro-chemical sensor for selective detection of 4-nitrophenol (4-NP), based on molecularly imprinted polymer (MIP) technology. MIP technology is the design of an artificial receptor with high selectivity for a specific analyte. Our approach combines N-isopropylacrylamide (NIPAM) backbone polymer with different functional monomers to improve the selectivity and sensitivity of 4-nitrophenol (4-NP) detection.
The key points of our sensor polymer are:1) reduced amount of covalent crosslinker methylene bis-acrylamide (MBA) to increase rebinding kinetics and affinity and 2) modified polymer backbone with an electroactive block deposited on a gold surface. To get rapid high affinity template rebinding, we used a reduced amount of covalent crosslinker and used noncovalent crosslinking based on acid-base and hydrophobic interactions. To form acid-base crosslinking, we used 4-vinylpyridine (4-VP) as the basic monomer and methacrylic acid (MAA) as acidic monomer.
In MIPs synthesis part, our strategy takes the advantage of reversible addition fragmentation-chain transfer (RAFT) polymerization to control the polymer chain length and modify the terminus as poly-ferrocene methyl methacrylate (FMMA), an electroactive block. The RAFT agent contains R group and Z group which are at different ends of polymer. The Z side is reduced to a thiol and deposited on gold. The PolyFMMA block is on the R side. RAFT agent, FMMA monomers and initiator were added to a batch system to synthesis the first electroactive block. Then, all chemicals including backbone monomers, functional monomers, crosslinkers and templates (4-NP) were added to form the major polymer block. After synthesis, templated-MIPs were dialyzed to remove the template for further target selective detection.
One of the major challenges of our sensor is polymer tangling which affect measurement stability. To reduce polymer tangling effects, we dissolved the template-removed MIPs into tetrahydrofuran (THF) and controlled the gold electrode surface coverage. We deposited MIPs on an additional flat gold chip and used atomic force microscope (AFM) to characterize the surface coverage distribution.
The modified gold electrode can be used in electrical impedance spectroscopy (EIS) or cyclic voltammetry (CV) to measure charge transfer distance before and after template rebinding to detect unknown concentration target analytes.
Synthesis and Modification of TiO2 nanostructured Materials for Energy Storage
Authors: van der Zalm Joshua , Salverda Allison , Chen Aicheng 
Published: May 2020

Increasing energy demand is inexorably linked to the need for efficient energy storage techniques. For practical applications, it is highly desirable to decrease the size of electrical components and to increase the storage capacities while maintaining power, stability, and charging-discharging speeds. Much focus has been directed towards the development of supercapacitors. These are often fabricated from carbonaceous or metal oxide materials with high surface areas to maximize electrode/electrolyte interactions. The use of nanostructured TiO2 electrodes has been explored for this application due to their low cost, high stability, and highly tunable morphology.
Here we present the fabrication of nanostructured TiO2 films via a facile anodic process. Characterization of the films was carried out by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Electrochemical reduction of the formed TiO2 film was further performed to increase its capacitance, which was confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. The performance of the symmetric capacitor constructed with the modified TiO2 films will be presented.