bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of Electrooxidation Products in Microfluidic Devices Using Raman Spectroscopy
Authors: Li Tianyu , Holm Thomas , Harrington David A.
Published: May 2020

Microfluidic devices combined with Raman Spectroscopy have great promise for in-situ and online detection of reaction processes with only a small volume of liquid required. This advanced method allows for flexible manipulation of fluids, micro/nano-particles, and biological samples1. Lab-on-a-chip applications are often used for chemical analysis, but Raman microscopy has also been used to monitor reactions within microreactors. The combination of the controlled mass transport in microfluidics with detection of soluble intermediate and product species by Raman offers the possibility of mechanistic kinetic studies of electrocatalytic reactions. We here show the feasibility of this method for studying electrocatalysis of oxidation of alcohols.

Two types of microfluidic flow devices were fabricated, which used glass slides and printed circuit boards (PCBs) as substrates, respectively. For glass-slide-based microfluidic devices, Raman spectra were used to monitor methanol oxidation catalyzed by a Pt mesh electrode, and calibration with known solutions enabled quantification of methanol and formate concentrations. A comparative study of catalytic oxidations of glycerol, ethanol, ethylene glycol and 1-propanol using electrodeposited Ni on carbon paper showed that under strong alkaline conditions, glycerol and ethylene glycol principally gave formate and carbonate products, while ethanol and 1-propanol did not give formate. Acetate was found to be the major oxidation product of ethanol, with only a small amount of carbonate. For PCB-based microfluidic substrates, electroplated Ni on Cu pads gave planar working electrodes, which were used to catalyze the oxidation of glycerol. On-board PdH reference electrodes were incorporated2.

1. A.F. Chrimes, K. Khoshmanesh, P.R. Stoddart, A. Mitchell, K. Kalantar-zadeh, Microfluidics and Raman microscopy: current applications and future challenges, Chem. Soc. Rev., 42, 5880 (2013).

2. E.V. Fanavoll, D.A. Harrington, S. Sunde, G. Singh and F. Seland, A Microfluidic Electrochemical Cell with Integrated PdH Reference Electrode for High Current Experiments, Electrochim. Acta., 225 , 69 (2017).

Acknowledgement: This research was conducted as part of the Engineered Nickel Catalysts for Electrochemical Clean Energy project administered from Queen’s University and supported by Grant No. RGPNM 477963-2015 under the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Frontiers Program.

Figure 1
Online Monitoring Purification of Molten Salt Using Electrochemical Method
Authors: Zhang Yingchun , Han Wei , Li Mei
Published: May 2020

In the reprocessing spent fuel, the waste molten salt needs to be purified in order to solve the massive accumulation of rare earth elements (RE). In this paper, square wave voltammetry (SWV) was applied to on-line monitoring the concentration change of RE (III) (RE=La, Sm, Nd, Dy) during RE precipitation using Na3PO4 as precipitator. SWV curves were measured by varying RE (III) concentrations analyzed by ICP-AES. After the measurement, the calibration curves about the linear relationship of RE (III) concentrations and peak current densities were obtained. The reproducible measurement conditions in a molten salt were investigated in terms of the principal parameters such as a pulse height and a wave frequency for getting a proper calibration curve. It was found that the peak current densities of SWV and concentrations of RE(III) were linear with the addition of Na3PO4. It is feasible to on-line monitoring the precipitation reaction by SWV.

Acknowledgement

The work was financially supported by the National Natural Science foundation of China (11675044, 21790373, 21876034 and 11875116), and the International Exchange Program of Harbin Engineering University for Innovation−oriented Talents Cultivation.
Electrically Conductive 2D Metal-Organic Framework/Graphene Composite for the Electrochemical Reduction of Nitrogen to Ammonia Under Ambient Conditions
Authors: Hassan Mohamed H. , Andreescu Silvana
Published: May 2020

The conversion of N2 into ammonia is one of the most important processes in the chemical industry and the basis for the production of fertilizers necessary to maintain agricultural food production. The conventional Haber-Bosch process requires high energy input (1% of world energy supply) and suffers from harsh reaction conditions with an associated CO2 emission as a side product. More sustainable alternatives for ammonia synthesis are thus needed to sustain the growing demand. Electrochemical reduction of N2 (NRR) is an attractive approach that utilizes catalysts that can selectively favor one reduction product over the others at a lower reduction potentials. Despite the unprecedented efforts in utilizing metal-organic frameworks MOFs in the electrocatalytic N2 reduction, their powdery nature, high electrical resistance, poor product selectivity and low stability limits their use in catalytic applications. This presentation will describe a facile one-pot synthesis method that can modulate MOF’s conductivity via growing 2D ultrathin copper/palladium-tetrakis (4-carboxyphenyl) porphyrin Cu(PdTCPP) layers interconnected with graphene sheets giving Cu(PdTCPP)@G. This technique favors the formation of free-standing large sheets of MOF/graphene. The strong interaction between the MOF and graphene sheets allows direct electron transfer through the MOF matrix enabling them to become electrically accessible. Palladium atoms act as the main catalytic sites for NRR in a system that offers high activity and selectivity giving NH3 yield rate of 5.45 µg h-1 mg-1 MOF (52 µg h-1 mg-1 Pd ) at -0.091 V vs RHE and a Faradaic efficiency of 8.45% in 0.1 M phosphate buffer. This material showed a very promising photocurrent generation making it attractive for further development of a photocatalytic NRR that can run under sunlight, with potential to become fully sustainable.
Electrochemical Behavior of U3O8 in LiCl-KCl-NH4cl Under Air Atmosphere
Authors: Liu Yichuan , Li Mei , Han Wei
Published: May 2020

In this work, the dissolution behavior of U3O8 in LiCl-KCl-NH4Cl melt was studied by electrochemical technique. The result of cyclic voltammetry (CV) indicated that the reduction/oxidation peaks of UO2
2+/UO2
+ , which meant U3O8 could dissolve in LiCl-KCl melt assisted by NH4Cl. Meanwhile, UO2
2+ was also measured by UV-vis absorption spectra and fluorescence emission spectra. Potentiostatic electrolysis was carried out at -2.4 V and -0.5 V for 2 h in LiCl-KCl-NH4Cl-U3O8 system, and the products were analyzed by scanning electron microscope and energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD). The results showed that U metal and UO2 were obtained on Mo cathode at -2.4 V and -0.5 V, respectively.

Acknowledgement

The work was financially supported by the National Natural Science foundation of China (11675044, 21790373, 21876034 and 11875116), and the International Exchange Program of Harbin Engineering University for Innovation−oriented Talents Cultivation.
An Investigation of Surface-Functionalized Electrocatalysts for Efficient CO2 Reduction to Multi-Carbon Products
Authors: Larrazábal Gastón O. , Chorkendorff Ib , Seger Brian
Published: May 2020

Despite rapid progress in the past few years, efficiently reducing CO2 to valuable multi-carbon products, such as ethanol and ethylene, remains a formidable challenge.[1] Overcoming the mechanistic hurdles in the path toward these compounds requires investigating new concepts in catalyst design while gaining fundamental insights into their mechanistic effect.

Several examples from (non-electrochemical) heterogeneous catalysis illustrate how adsorbed organic ligands can be used to tune activity and selectivity due to the emergence of electronic and geometric effects,[2] but this powerful strategy of using surface modifiers remains relatively unexplored in the context of CO2 reduction. Nevertheless, recent reports provide compelling evidence of its potential: for instance, Buonsanti et al. showed the promoting effect on CO evolution of imidazolium-based ligands anchored to the surface of silver nanoparticles,[3] and a recent publication by Sargent et al. demonstrated how N-aryl-pyridinium-functionalized copper electrodes attain high Faradaic efficiency for CO2 reduction to ethylene at elevated current densities.[4]

In this contribution, we show how the adsorption of sub-monolayer coverages of small organic ligands influences the eCO2RR selectivity patterns of well-defined metallic surfaces. In tandem with the characterization of the functionalized surfaces by x-ray photoelectron and infrared spectroscopies, these findings provide unique insights into the impact of adsorbed organic molecules on CO2 reduction, informing the development of a new strategy with the potential to achieve breakthrough advances toward the production of multi-carbon compounds.

[1] S. Nitopi, E. Bertheussen, S.B. Scott, X. Liu, A.K. Engstfeld, S. Horch, B. Seger, I.E.L. Stephens, K. Chan, C. Hahn, J.K. Nørskov, T.F. Jaramillo, I. Chorkendorff, Chem. Rev.
2019, 119, 7610-7672

[2] M.A. Ortuño, N. López, Catal. Sci.
Technol.
2019, 9, 5173-5185

[3] J.R. Pankhurst, Y.T. Guntern, M. Mensi, R. Buonsanti, Chem. Sci.
2019, 10, 10356-10365

[4] F. Li, A. Thevenon, A. Rosas-Hernández et al., Nature
2019, DOI:10.1038/s41586-019-1782-2
Electrocatalytic Urea and Ammonia Oxidation for Cell Voltage Optimization in CO2 Electrolyzers
Authors: Medvedeva Xenia , Medvedev Jury , Tatarchuk Stephen , Klinkova Anna
Published: May 2020

Considering the continuous growth of carbon dioxide emissions and resulting climate change, the electrochemical reduction reaction of CO2 (CO2RR) to fuels and other valuable compounds is a promising strategy for utilizing the emitted greenhouse gas. The most current CO2RR approaches rely on the oxygen evolution reaction (OER) as the anodic process, which requires high potentials (Eo = 1.23V vs SHE) and produces low-value O2 as a product. The electrochemical CO2 conversion to CO or valuable carboxylic acids coupled with an alternative useful anodic reaction with a lower energy requirement than that for OER, could be a good strategy for lowering the cell potential. Based on the thermodynamic calculations of standard reaction Gibbs free energies and standard cell voltages for various anodic reactions, we demonstrate that the anodic oxidation of urea (UOR) and ammonia (AOR) are excellent alternatives to the OER in the CO2 electrolyzers for reducing its energy consumption. At the same time, performing UOR and AOR along with CO2RR introduces additional environmental value to the overall process, as these anodic reactions can be used for wastewater treatment. We evaluate the performance of divided batch and flow electrochemical cells, with CO2RR at the Ag and Au cathodes coupled with UOR and AOR at Ni-based and Pt-based anodes. The replacement of OER with Ni3+-catalyzed UOR decreases the operating cell potential by ≈250mV at current densities of up to 100mA cm-2, while enabling high faradaic efficiencies of CO formation at the cathode. Further decrease in cell potential of [CO2RR | UOR] electrolyzer is challenging due to the relatively high thermodynamic potential of Ni2+ to Ni3+ oxidation (Eo = 0.49V vs SHE). However, we show that the replacement of OER with AOR at Pt/C can decrease the operating cell potential by ≈700mV at current densities of up to 2mA cm-2 limited by the poor activity of current state-of-the-art catalysts for AOR. Finally, we establish an electrochemical system for the efficient CO2 conversion to CO coupled with UOR and AOR that operates at lower cell potentials, than that of OER.
Gold-Copper Metal Alloys: Crystalline Materials for the CO2 Reduction Reaction
Authors: Adserias Albert , Leach Gary W.
Published: May 2020

Chemical fixation of CO2 into fuels has been the focus of intense research interest due to growing energy demands and the cumulative environmental impact associated with fossil fuel consumption. Reduction of CO2 to CO and hydrocarbons therefore represents an opportunity to close the carbon cycle. Despite much progress, improvements in CO2 reduction activity, and catalyst stability are required to transform existing catalyst materials into viable candidates for this purpose. Here, we describe our efforts to develop new gold-copper alloy materials for application in CO2 reduction. We employ recent metal deposition technology developed in our laboratory that enables single-crystal epitaxial noble metal deposition from solutions containing their simple metal salts. The Au-Cu metal pair has been selected due to its chemical stability and catalytic properties. Co-deposition from solutions comprised of Au- and Cu-containing metal salts allows the fabrication of Au-Cu alloys of controlled composition. We describe the fabrication and characterization of Au-Cu alloy materials using a wide range of techniques including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and high resolution transmission electron microscopy. We have also investigated the alloy elelctrocatalytic activity through linear sweep voltammetry and chronoamperometry to establish catalytic activity and correlate the activity with catalyst structure and composition.
Spectroscopic Evidence for the C2O4
− Dimer Radical Anion during Electrochemical CO2 Reduction on Cu Electrodes in Aqueous Conditions
Authors: Moradzaman Mozhgan , Mul Guido
Published: May 2020

Understanding of reaction pathways and mechanism plays an important role in determining the kinetics of electrochemical reactions, and thus in the design of electrochemical processes. Attenuated Total Reflection - Surface Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) provides a very sensitive tool for analysis of surface-electrochemical transformations. One of the applications of this technique is operando study of the electrochemical reduction of CO2. However, there is still much uncertainty concerning the nature of the intermediates towards CO in the conversion of CO2, and the interpretation of the measured peak positions in the IR spectra.

In this study, ATR-SEIRAS allowed identification of notable intermediates of electrochemical CO2 reduction at moderately negative potential ranges using a surface enhanced ~12 nm thick sputtered Cu-film and isotopically labeled water (D2O) and CO2 (13CO2). By increasing the potential from -1.3 V (vs RHE) to 0 V, we could identify the transition in selectivity of surface-adsorbed species. At highly negative potential the formation of OH- and H2 is dominant, resulting in a relatively high concentration of carbonate in solution. When the potential is lowered, the rate of H2 formation decreases, which induces lowering of the concentration of carbonate and increased quantities of bicarbonates, a transition which is spectroscopically well resolved. To explain the formation of CO (clearly visible within the investigated potential range), alternatively or additionally to H+-assisted reduction of CO2, adsorbed CO2
- is shown to react with physisorbed CO2, forming the CO2 dimer radical anion. We could identify this CO2 dimer radical anion (C2O4
−) on polycrystalline copper electrodes, at moderately negative potentials. Decomposition of the dimer leads to CO and (surface) carbonate. Finally, at the lowest potentials investigated for reduction of CO2, the formation of (surface) formate is evident, which cannot be further reduced.
Highly Selective Electroreduction of CO2 to CO over Zinc Nanostructures
Authors: Xiao Jing , Gao Minrui , Luo Jing-Li
Published: May 2020

To mitigate CO2 emissions and enable the conversion of CO2 to carbon-neutral fuels, the research on electrochemical reduction of CO2 (CO2RR) is gaining momentum and so is the search for an earth-abundant electrocatalysts to achieve high catalytic activity and desirable selectivity for the target fuel. Herein, we synthesized hexagonal Zn nanoplates (H-Zn-NPs) and systematically explored its shape-dependent catalytic activity for CO2RR, so as to achieve a better understanding of the relationship between the morphology and the catalytic activity of non-noble metal catalysts. The prepared H-Zn-NPs are found to efficiently promote CO2RR toward CO production with improved catalytic activity, good stability and remarkably high CO selectivity of over 85% in a broad potential range. Theoretical results reveal that the unique hexagonal Zn nanostructure offers an increased number of catalytically active sites which are active for CO2RR to CO. The H-Zn-NPs undoubtedly hold a great potential as an alternative to noble metal for highly selective CO2RR to CO.
Porous Metallic Membranes As High-Performance Gas Diffusion Electrodes for CO2 Reduction in a MEA-Type Electrolyzer
Authors: Larrazábal Gastón O. , Laursen Asger J. , Chorkendorff Ib , Seger Brian
Published: May 2020

Combining the electrochemical reduction of CO2 (eCO2RR) with carbon-neutral energy sources creates groundbreaking possibilities for using CO2 as a raw material for the sustainable production of fuels and chemicals. Recent technoeconomic analyses have emphasized the importance of achieving high current densities (i.e., hundreds of mA cm‒2) for the eCO2RR to be practically viable,[1] leading to a growing awareness of the need to evaluate catalysts under industrially-relevant operating conditions.[2]

Cell designs that integrate selective eCO2RR catalysts into a membrane electrode assembly (MEA) are a promising approach to reduce ohmic losses and achieve high energy efficiency at elevated current densities.[2,3] In this context, we recently demonstrated that unmodified silver membranes—commonly used as porous filtration media in biotechnological applications—sustain high rates of CO2 reduction to CO (> 200 mA cm‒2) when used as gas diffusion electrodes (GDEs) in a zero-gap configuration.[4] These metallic electrodes are simple, highly stable, and cost-competitive vis-à-vis carbon-based GDEs. However, CO2 crossover across the anion-exchange membrane (AEM)—required to suppress the hydrogen evolution reaction—results in poor reactant utilization and in the early onset of mass transfer limitations. These findings highlight the importance of carrying out a carbon balance, in addition to traditional measurements of activity and selectivity, to adequately assess the performance and to identify the operational limitations of realistic devices for CO2 reduction.

We will also discuss how these porous silver membranes can be employed as templates for the synthesis of freestanding copper GDEs and, particularly, how different electrode morphologies and compositions can be targeted via the synthesis procedure to tune the resulting selectivity toward multi-carbon products. In addition, we will show how the homogeneous structure and uniform pore network of these porous metallic membranes provides insights into the influence of the GDE’s mass transport properties on CO2 reduction in a zero-gap configuration.

[1] M. Jouny, W. Luc, F. Jiao, Ind. Eng.
Chem. Res.
2018, 57, 2165-2177

[2] T. Burdyny, W.A. Smith, Energy Environ Sci. 2019, 12, 1442-1453

[3] D. Higgins, C. Hahn, C. Xiang, T.F. Jaramillo, A.Z. Weber, ACS Energy Lett.
2019, 4, 317-324

[4] G.O. Larrazábal, P. Strøm-Hansen, J.P. Heli, K. Zeiter, K.T. Therkildsen, I. Chorkendorff, B. Seger, ACS Appl. Mater. Interfaces
2019, 11, 41281-41288
Coupling of Various Aqueous Anodic Reactions with Direct and Indirect Electroreduction of CO2 in Organic Media
Authors: Medvedev Jury , Medvedeva Xenia , Li Feng , Klinkova Anna
Published: May 2020

The electrochemical reduction of CO2 (CO2RR) to useful chemicals such as hydrocarbons, alcohols, and carboxylic acids is a promising CO2 utilization strategy. However, CO2RR in aqueous media requires high electricity input due to the chemical inertness of CO2, its poor solubility in water, and the reliance on the sluggish oxygen evolution reaction (OER) at the anode. Here, we investigate how alternative reaction designs within a CO2 electrolyzer can address these issues. Specifically, we explore the effect of changing catholyte medium, cathodic reaction pathway, and oxidizing substrates at the anode on the electrolyzer performance and energy requirement. First, we perform CO2RR in aprotic electrolytes that not only increase the solubility of CO2, but also eliminate competing hydrogen evolution reaction. Second, we introduce organic precursors (organic halides) in aprotic media to produce electrochemically generated nucleophiles, which can react with CO2 at lower potential than required for direct CO2 activation, yielding a variety of useful carboxylic acid (indirect CO2RR). Third, we couple both direct and indirect CO2RR in organic medium with aqueous anodic reactions associated with wastewater treatment (urea and ammonia electrooxidation) that require a significantly lower energy input than OER. We investigate the advantages and limitations of ion-exchange membranes of different types that render efficient aprotic and aqueous compartment segregation to conduct these reactions within a single cell. We also elucidate the effects of the electrolyzer operating parameters (applied potential, organic precursor concentration, temperature) on the efficiency and selectivity of CO2RR. In addition, we propose a detailed mechanism of direct and indirect CO2RR in organic electrolytes based on density functional theory calculations and extensive experimental results.
Ammonia Thermal Treatment Toward Topological Defects in Porous Carbon for Enhanced Carbon Dioxide Electroreduction
Authors: Dong Yan , Gyenge Előd L.
Published: May 2020

Abstract

The design of specific active sites for the carbon dioxide electro-reduction reaction (CO2RR), is crucial for determining product selectivity and catalysis performance. Here, we present an efficient NH3 thermal treatment for thoroughly removing the pyrrolic-N and pyridinic-N dopants from 3D N-enriched graphene analogue particles, to create high density of topological defects as active sites for CO2RR.[1] Firstly we found that NH3 showed a pronounced effect of eliminating specific N-containing moieties at elevated temperatures, superior to Ar. The identification of topological defects (pentagonal carbon polygon and 585 defect) was investigated by near-edge X-ray absorption fine structure measurements and local density of states analysis, and its formation mechanism was revealed by reactive molecular dynamics simulations.The as-prepared catalysts exhibited excellent performance in flooded half-cell experiments in 0.1 M KHCO3 reaching current densities of 2.8 mA cm-2 and 4.4 mA cm-2 with FECO of 92.7% and 89.2% at -0.6 V and -0.7 V v.s. RHE, respectively at room temperature and atmosphere pressure. These results are among the best performances reported for metal-free catalysts.[2,3,4,5] Density functional theory calculations revealed that the edged pentagonal sites (penta-1 and 585-1 defects) are the dominating active centers with the lowest free energy barriers of CO2RR for CO production.[6,7]

References

[1] Zhu J.; Huang J.; Mei W. et al, Angew. Chem. Int. Ed.
2019, 58, 3859-3864

[2] Wu, J.; Liu, M.; Sharma, P. P. et al, Nano Lett.
2016,
16 (1), 466-70

[3] Wu, J.; Yadav, R. M.; Liu, M. et al, ACS Nano
2015,
9 (5), 5364-5371.

[4] Daiyan, R.; Tan, X.; Chen, R. et al, Acs Energy Lett.
2018,
3 (9), 2292-2298.

[5] Kumar, B.; Asadi, M.; Pisasale, D. et al, Nat. Commun.
2013,
4, 2819.

[6] Banhart F., Kotakoski J., Krasheninnikov A.V. ACS Nano,
2011
, 5, 29-41.

[7] Dong, Y.,zhang Q.J. et al, Ammonia Thermal Treatment toward Topological Defects in Porous Carbon for Enhanced Carbon Dioxide Electroreduction. (submitted)

Figure 1
New Materials for Electrocatalysis: Ionic Liquids and Metal Nanocrystals
Authors: Zeng Xiangqun , Liu Xiaojun , Tang Yongan
Published: May 2020

There have been two methods to generate electrocatalysts: one is by structural or chemical modifications of the electrode surface, another is by the interface reactions in the electrolyte. Ionic liquids (ILs) are liquids often composed of bulky organic cations or anions that have found wide applications in energy-related and gas-sensor technologies. Being composed entirely of ions and with a broad structural and functional diversity [i.e., hybrid (organic/inorganic), biphasic (solid/liquid), and bifunctional (solvent/electrolyte) materials], non-aqueous organic IL electrolytes can promote the formation of the radical catalysts for electron transfer reactions since ILs can stabilize radical cations and anions by electrostatic forces and van der Waals forces. In parallel, nanomaterials such as metal nanocrystals with controlled surface structures are able to maximize the sensitivity and selectivity of electrochemical interface reactions since metal nanomaterials could provide both high surface areas and high catalytic activity. This presentation will discuss the fundamental and applied ionic liquid (IL) and metal nanomaterials electrochemistry research in our laboratory to illustrate that new catalytic reactions can be generated in situ at IL-electrode interface utilizing the benefits of both nanomaterial electrode and the IL electrolyte catalysts for oxidation or reduction of important gaseous compounds (methane, oxygen, hydrogen, carbon monoxide, methanol etc).
Bio-Inspired Polydopamine Mimic Noble Metal Electrocatalysts in Hydrogen Evolution Reaction
Authors: Coskun Halime
Published: May 2020

The main electrocatalysts for the electrochemical hydrogen evolution reaction (HER) rely on platinum due to high efficiencies, low binding energy for hydrogen and high electroactive-site density, however the cost of platinum is a crucial limitation for the production of hydrogen by this rare metal.[1] Here, we establish a metal-free and bio-organic electrocatalyst platform that resembles the platinum surface by incorporating hydrogen-affine hydrogen bonds. We introduce keto-amine functional motifs, which act as selective reaction centres.[2, 3] The keto-amine-functionalized biopolymer shown in this work evolve hydrogen at the lowest overpotential in a non-metallic system. With excellent electrochemical stability and chemical robustness, we are able to present a scale-up continuous-flow electrolysis and produce 1 L net molecular hydrogen within less than 9 hours using 2.3 mg of biopolymer electrocatalyst.

[1] Y. Zheng, Y. Jiao, Y. Zhu, L.H. Li, Y. Han, Y. Chen, A. Du, M. Jaroniec, S.Z. Qiao, Hydrogen evolution by a metal-free electrocatalyst, Nature Communications, 5 (2014) 3783.

[2] H. Coskun, A. Aljabour, P. De Luna, D. Farka, T. Greunz, D. Stifter, M. Kus, X.L. Zheng, M. Liu, A.W. Hassel, W. Schofberger, E.H. Sargent, N.S. Sariciftci, P. Stadler, Biofunctionalized conductive polymers enable efficient CO2 electroreduction, Science Advances, 3 (2017).

[3] H. Coskun, A. Aljabour, L. Uiberlacker, M. Strobel, S. Hild, C. Cobet, D. Farka, P. Stadler, N.S. Sariciftci, Chemical vapor deposition - based synthesis of conductive polydopamine thin-films, Thin Solid Films, 645 (2018) 320-325.
The Stability of Sulfur Stabilized Pt Single Atom Electroatalyst
Authors: Paul Michael T. Y. , Speck Florian Dominik , Zepeda Francisco Ruiz , Gatalo Matija , Hodnik Nejc , Mayrhofer Karl J. J. , Choi Changhyuck , Cherevko Serhiy
Published: May 2020

Single atom catalysts (SACs) are of great interest in recent scientific development because they possess the highest possible mass specific activity compared to conventional nanoparticle (NP) based catalysts. Therefore, the use of SACs is especially attractive for applications where noble metal catalysts are required. The enhanced mass activity can aid in reducing the metal loading, and thus the cost of these systems. Due to the reduction in metal loading, the stability of SACs is critical for ensuring their long-term electrochemical performance. In this study, the stability of high S content carbon supported Pt SACs was investigated by using electrochemcial accelerated stress tests (ASTs). The amounts of dissolved S and Pt were directly measured in relations to applied potentials. These dissolved ions were detected in-situ through the use of a scanning flow-cell (SFC) connected to an on-line inductively coupled plasma mass spectrometer (ICPMS). The morphological and elemental changes of the catalyst were also examined by identical location transmission electron microscopy and X-ray spectroscopy before and after the ASTs. The interactions between Pt SACs and S surface groups were probed by series of experimental designs. The results indicated that these S stabilized Pt SACs were significantly more stable when compared to their NP-based counterparts, and there exists a possible mutual interaction between S and Pt SACs.
Structure Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction
Authors: Li Jiazhan , Cullen David A. , Wang Guofeng , Feng Zhenxing , Wu Gang
Published: May 2020

FeN4 moieties embedded in partially graphitized carbon are the most efficient platinum group metal free active sites for the oxygen reduction reaction in acidic proton‐exchange membrane fuel cells. However, their formation mechanisms have remained elusive for decades because the Fe−N bond formation process always convolutes with uncontrolled carbonization and nitrogen doping during high‐temperature treatment. Here, we elucidate the FeN4 site formation mechanisms through hosting Fe ions into a nitrogen‐doped carbon followed by a controlled thermal activation. Among the studied hosts, the ZIF‐8‐derived nitrogen‐doped carbon is an ideal model with well‐defined nitrogen doping and porosity. This approach is able to deconvolute Fe−N bond formation from complex carbonization and nitrogen doping, which correlates Fe−N bond properties with the activity and stability of FeN4 sites as a function of the thermal activation temperature.
Metal–Organic Frameworks-Derived Ptm Intermetallic Nanoparticles for Oxygen Reduction in Proton Exchange Membrane Fuel Cells
Authors: Qiao Zhi , Wang Chenyu , Spendelow Jacob S , Wu Gang
Published: May 2020

Highly ordered PtM intermetallic alloy structures are proven effective to improve their catalytic activity and stability for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Here, we discuss our recent progress to prepare ordered PtCo intermetallic nanoparticles derived from atomically metal site-doped metal–organic-framework (MOF). In particular, the atomically dispersed Co sites, which are originally embedded into MOF-derived carbon, diffuse into Pt nanocrystals and form ordered Pt3Co structures. It is very crucial for the formation of the ordered Pt3Co to carefully control the doping content of Co into the MOFs and the heating temperatures for Co diffusion. In this presentation, detailed catalyst synthesis, extensive characterization, and comprehensive RDE tests and fuel cell evaluation will be discussed.
Electron Transfer of Shewanella Oneidensis MR-1 atClay-Modified ITO Electrode
Authors: Alshehri Reem , Fitch Alanah
Published: May 2020

The role of structural iron in clays to enhance the electron transfer of Shewanella Oneidensis MR-1 was investigated. Three types of clays containing different amounts of iron situated in the octahedral sites have been used to modify the ITO electrodes: nontronite NAu-1, montmorillonite (Wyoming) SWy-1, and synthetic montmorillonite SYn-1. The interaction between bacterial cells and the clay, which modified the ITO electrodes were studied by potential step, cyclic voltammetry, confocal microscope, and scanning electron microscope SEM. Experimental results showed that the current density generated using iron containing clays NAu-1 and SWy-1 to modify the ITO electrode was 19 and 3 times higher than that produced using the bare ITO electrode. Mechanism of electrochemical production deviated for the iron containing clay NAu-1

Keywords

Shewanella Oneidensis MR-1, Clay, Modified ITO electrode, MFC
(Invited) Nonaqueous Redoxmer Flow Batteries: New Opportunities for Size-Exclusion Using Nanoporous Separators
Authors: Helms Brett A. , Moore Jeffrey S , Rodriguez-Lopez Joaquin
Published: May 2020

Nonaqueous redox flow batteries (NRFBs) are attractive devices for energy storage due to an increased potential window and the manifold possibilities they offer in terms of redox-active architectures and chemistries available for increasing energy density and battery performance. Our collaborations in the context of the Joint Center for Energy Storage Research (JCESR) have shown that pairing commercial nanoporous separators with redoxmer architectures[1] such as Redox-Active Polymers (RAPs),[2] Redox-Active Colloids (RACs),[3] and Redox-Active Oligomers (RAOs),[4] effectively prevent crossover of the active component within the flow system. The choice of redoxmer size and chemical makeup impact profoundly the electrochemical dynamics of the NRFB, and it is clear that optimal performance is only attained with a balanced pairing between redoxmer and separator membrane. In this presentation, I will discuss the design principles underlying size-exclusion NRFBs and some current directions on how nanoporous separators enable new strategies for long-term performance in the flow battery. I will highlight how the progression from high polymers to oligomers modifies the charge transfer characteristics of NRFB electrolytes and the implications of the dynamics of these redoxmer solutions on the size-exclusion approach.[5] Unlike small molecules, the electrochemical reactivity of solution-phase redoxmers is strongly modulated by the properties of both surface confined and freely diffusing species. Building from this knowledge, the recent introduction of Polymers of Intrinsic Microporosity (PIM) separators[4] into the NRFB scene area allows new opportunities in the design of redoxmers with improved charge transfer characteristics and diffusivity without sacrificing their size-exclusion performance. Finally, the use of a size-exclusion approach enables advanced concepts for long-term maintenance of a battery system. I will discuss recent results where controlled de-polymerization reactions are used for maintaining the state-of-health of NRFB components, highlighting the role of component separation using our strategy. Altogether, the combination of novel structural motifs and the use of new nanoporous materials, results in new directions to make better NRFBs that exploit the versatility of a new type of reacting redoxmer fluids for energy storage.

References:

[1] Acc. Chem. Res. 2016, 49, 2649.

[2] J. Am. Chem. Soc. 2014, 136, 16309.

[3] J. Am. Chem. Soc. 2016, 138, 13230.

[4] Chem. Mater. 2018, 30, 3861.

[5] J. Electrochem. Soc. 2017, 164, A1688.
On the Performance and Structural Stability of Cathodic Electrocatalysts with Complex Nanoscale Morphology
Authors: Li Feng , Medvedeva Xenia , Medvedev Jury , Ahmed Aftab , Klinkova Anna
Published: May 2020

Increasing complexity of nanosynthesis has produced a variety of intricate nanoparticle shapes which have attracted significant attention for applications in electrocatalysis. These complex nanoelectrocatalyst shapes not only introduce high surface areas and high energy active sites, but also improve electrocatalytic performance by altering electric field at the surface thereby concentrating reagents and accelerating electrocatalysis. However, long-term structural stability of complex nanoelectrocatalysts necessary for their industrial implementation often remains unknown and difficult to predict. Here, we study structural stability in cathodic reactions (CO2 and water electrolysis) of noble metal nanoparticles with star- and core-cage structures that collectively cover major structural nanoscale features including extrusions, holes, voids, and nanogaps. Based on structural and surface analysis, density functional theory and finite element method calculations, we demonstrate that uneven electric field and current density distributions in these morphologies influence metal mobility resulting in their structural degradation. Our results revealed that extrusions and holes facing the anode form electric field hot spots for electrolysis, that also facilitate surface reconstruction. The holes and voids perpendicular to the direction facing the anode form current crowding spots within the metal that facilitate electromigration via local Joule heating, while being blind spots for electrolysis due to low local electric field in these areas. Finally, structural features within nanocages are electrically shielded resulting in them being blind spots for both electrolysis and electromigration. This study provides guidelines for the structural design of electrocatalysts, highlighting that it should not only be dictated by the surface atomic organization and the generation of electric field hotspots, but also by current distribution within the electrode itself, to ensure not only high material performance but also improved stability.
Microstructure and Transport Phenomena
Authors: Kuss Christian
Published: May 2020

Lithium ion mobility is one of the key properties that all battery materials need to exhibit for a Li-ion battery that functions reversibly and effectively. Within the battery, active materials are responsible for reversible intercalation, that requires the transport of Li-ions within the solid lattice. Outside the active material, the electrolyte shuttles Li-ions between the two electrodes. In between those materials, ion transport phenomena at the interfaces has been reported as having potentially significant impact on battery performance.

We are here reporting our efforts in tracking Li+ transport in LiFePO4 and solid electrolyte composites. Having found a significant role of microstructure in ionic transport, this presentation is further dedicated to our recent exploration of microstructure and improved electrode interfaces. Using active microscopy techniques, new methods are being developed in the imaging and quantification of microstructural properties. These techniques are applied to the comparison of a new conductive binder system to the traditional PVDF/C electrode matrix. These studies are contributing to the underexplored issue of microstructural effects on battery performance, and highlight alternatives to composite electrode composition and microstructure control.
Coconut Shell-Derived Activated Carbon: A Promising Electrode for High-Performance Capacitive Deionization (CDI) System
Authors: Le Viet Hai , Huynh Le Thanh Nguyen , Vo Anh Tuan , Nguyen Hoang Thai
Published: May 2020

Capacitive deionization (CDI) is a potential technique for water treatments such as brackish water desalination, seawater desalination, wastewater remediation, and water softening. CDI has more advantages over other desalinating processes: (i) the technique works by the process of electroabsorption, and is even more energy-efficient, as it does not require any high-pressure pumps; (ii) as the module works in 0.8–2.0 V. An ideal electrode for CDI system requires the following characteristics: (i) large surface area; (ii) high porosity (both meso and micropores); (iii) high electrical conductivity; (iv) electrochemical stability; (v) bio-inertness; (vi) fast adsorption-desorption kinetics; (vii) good wetting behavior; (viii) low cost; and (ix) scalability. In Vietnam, coconut shell-derived activated carbon is produced by a calcinated process under nitrogen gas, which exhibits a high surface area (800-1000 m2/g). In this work, we prepared the CDI composite electrode based on coconut shell-derived activated carbon and high conductive carbon like CNTs or carbon black in the pilot scale. CDI systems with a capacity of 1 m3 per day were fabricated and monitored the desalination performance in Mekong Delta.
(Invited) Understanding Dynamical Stability of Batteries and Catalysts with First-Principles and Ex-machina Computations
Authors: Kozinsky Boris
Published: May 2020

Electrochemical stability windows of electrolytes largely determine the limitations of operating regimes of lithium-ion batteries, but the degradation mechanisms are difficult to characterize and poorly understood. Using computational quantum chemistry to investigate the oxidative decomposition that govern voltage stability of multi-component organic electrolytes, we find that electrolyte decomposition is a process involving the solvent and the salt anion and requires explicit treatment of their coupling. We find that the ionization potential of the solvent-anion system is often lower than that of the isolated solvent or the anion. This understanding of the oxidation mechanism allows to formulate a simple predictive model that explains experimentally observed trends in the onset voltages of degradation of electrolytes near the cathode. This model opens opportunities for rapid rational design of stable electrolytes for high-energy batteries.

Design of materials based on dynamical and transport properties, important for batteries and catalysts, involves systematic exploration of many structural and compositional variations and hence requires very fast and accurate computations of dynamical phenomena. I will present recent progress and challenges in “ex-machina” materials design, a new paradigm in which an automated closed-loop machine learning algorithm constructs non-parametric Bayesian force fields that combine first-principles accuracy with internal quantitative uncertainty and prior information of physical symmetries. We apply this method, implemented in the FLARE framework [1], to large-scale dynamics simulations of alloys, ion conductors, catalysts and 2D materials.

[1] J. Vandermause, S. B. Torrisi, S. Batzner, A. M. Kolpak, B. Kozinsky, “On-the-Fly Bayesian Active Learning of Interpretable Force-Fields for Atomistic Rare Events”, (2019), arXiv:1904.02042
Non-Monotonic Change of Hydroxide Ion Diffusion with Increasing Temperature in Anion Exchange Membranes
Authors: Zelovich Tamar , Vogt Leslie , Tuckerman Mark E.
Published: May 2020

The development of reliable, cost-effective polymer architectures for use as anion exchange membranes (AEMs) is an important challenge for emerging electrochemical device technologies. In this work, we present a fully atomistic ab initio molecular dynamics study of carefully designed idealized AEM models using nano-confined structures, in order to obtain a molecular-level understanding of the effect of temperature on hydroxide ion diffusion mechanisms in AEMs. We find that the hydroxide ion diffusion coefficient changes non-monotonically with increasing temperature. While this is consistent for all systems, the specific reasons underlying this behavior depends on the level of hydration. Furthermore, while the diffusion of water molecules and hydroxide ions do not necessarily share the same trends, we find that the water structure, distribution, and mobility have a major impact on the hydroxide ion diffusion at all temperatures. The results presented in this study enable us to define the optimal temperature requirements to achieve high hydroxide conductivity, for each setup of AEM model.
Lithium Bond Chemistry at the Interlayer for High-Performance Lithium Sulfur Batteries
Authors: Duangdangchote Salatan , Phattharasupakun Nutthaphon , Joraleechanchai Nattanon , Sawangphruk Montree
Published: May 2020

Lithium-sulfur battery (LSB) is a promising candidate as a conventional lithium-ion battery substitute due to its high theoretical specific capacity and high energy density together with additional advantages of low cost, abundance, and environment friendliness. However, LSB is still hindered from commercialize scale due to its many challenges including insulator of reactant sulfur (S8) and final product (Li2S), polysulfide shuttle effect, and volume expansion during cycling. These issues cause the capacity fading and low efficiency in the LSB. To overcome the mentioned above issue as well as improve performances of the LSB, the modified carbon fiber interlayer has introduced between the sulfur cathode and separator in order to suppress the lithium polysulfide intermediates (LPSs) diffusion through the lithium bond. The lithium polysulfide intermediate can occur the chemisorption with functionalized group on the interlayer which can fundamentally explain by density functional theory (DFT) calculations. More interestingly, we also prove that the performance of the LSB is in a correlation with strength of the lithium bond between the interlayers and LPSs. We hope that this study should be a useful information in term of the chemistry of lithium bond which can enhance performance and safe operation of LSBs.1-3

Keywords: Carbon fiber interlayer, Lithium bond, Li-S battery

REFERENCES

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Figure 1
(Invited) Black TiO2 Nanotubes As Functional Supports and Electrodes
Authors: Schmuki Patrik
Published: May 2020

TiO2 nanomaterials have over the last 30 years attracted tremendous scientific and technological interest. A main research direction for TiO2 in functional applications is its use in photocatalysis, e.g. for the direct splitting of water into H2 and O2 to generate the potential fuel of the future, hydrogen. In order to achieve a maximum reaction rate, high surface area substrates, usually nanoparticles are used either suspended or compacted to a photoelectrode. Over the past decades, various 1D and highly defined TiO2 morphologies were explored for the replacement of nanoparticle networks and were found in many cases superior to nanoparticles. However, in every case the kinetics of H2 generation is sluggish from a plain TiO2 surface and noble metal cocatalysts are needed to reach accelerated reaction rates. Only recently it has been shown that TiO2 can be intrinsically activated by generation of suitable surface defects. Such material of a “gray” or “black” color can be generated with various treatments of many titania polymorphs and morphologies. The presentation will focus on highly ordered nanotube arrays of TiO2 and discuss most recent progress in synthesis and modification for photocatalytic and photoelectrochemical H2 generation. Of special interest is the formation of black TiO2 nanotubes by various reductive treatments. Black titania produced by high pressure hydrogenation has been demonstrated to enable noble-metal-free photocatalytic H2 generation. TEM, EPR, and XPS investigations as well as photoelectrochemistry are used to characterize different degrees of surface hydrogenation, surface termination, electrical conductivity, and structural defects in the differently reduced titania nanotubes. These investigations find that the formation of intrinsic photocatalytic hydrogen evolution activity is induced by optimized and specific defect formation.