bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cathodically Deposited Birnessite As the Electrode Material
Authors: Pugolovkin Leonid V. , Levin Eduard E. , Arkharova Natalya A , Orekhov Anton , Presnov Denis E , Tsirlina Galina A. 
Published: May 2020

Various manganese oxides are considered as rather active ORR catalysts and/or supercapacitor materials for operation in alkaline medium. However all these oxides are thermodynamically unstable at high pH and undergo more or less slow transformations to non-stoichiometric oxides containing alkali metal cations M (MxMnO2*nH2O, known also as birnessite mineral). We report a possibility to deposit birnessite thin layers by means of permanganate cathodic reduction. We consider ORR activities and reversible recharging data for birnessite deposited at various potentials with account for XRD information on birnessite cell disordering and microscopic data on the morphology of the deposits.
Deposition is complicated by formation of soluble Mn(V) and Mn(VI) species and their disproportionation. However fortunately these by-side reactions appear to be strongly inhibited by forming birnessite solid, and the resulting current efficiencies are high enough. We compare deposition efficiency and adhesion for Pt, Ni, and glassy carbon supports. The best adhesion is found for Ni support.
Deposits morphology strongly depends on deposition potential. Thin deposits formed at low overvoltage demonstrate homogeneously distributed pores, and only starting from sub-mkm thickness branched flakes appear, which are typical for natural birnessite morphology. Contrary, at higher overvoltage the deposits start to branch from the very beginning, and consist from thin flakes exclusively. This morphology is unfavorable for electrode behavior because of too high material resistance. Deposition transients allow to monitor the morphology. For flakes formation, oscillatons at deposition transients are observed, which can be associated with layer-by-layer growth.
The recharging of all birnessite materials is reversible, but the specific capacity strongly depends on deposition potential and deposit thickness. The best results (ca. 500 mkF/cm2 at scan rates up to 0.1 V/s) are found for thin deposits fabricated at low overvoltage. ORR mass activity is comparable with observed earlier for MnO2, which is believed to undergo slow transformation to birnessite in alkaline solutions. The important advantage of electrodeposited birnessite as compared to the majority of chemically synthesized manganese oxides is a possibility to operate in the absence of conducting binder.
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
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
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.
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
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
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.
(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.
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.
(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