bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tuning Binding Energy in Nanoporous Core Shell Alloys of Palladium to Suppress CO Poisoning in Electrochemical Reduction of CO2
Authors: Chatterjee Swarnendu , Li Yawei , Snyder Joshua David 
Published: May 2020

Electrochemical CO2 reduction reaction (CO2RR) has been extensively explored for conversion of dissolved CO2 into useful carbon based products e.g CO, formate/formic acid, alcohols etc. Formate/formic acid as a CO2RR product is drawing focus because of its high energy density and utility as a chemical precursor. Traditional formate producing metals e.g. Co, In, Bi, Sn etc. require high overpotentials, limiting their energy effectiveness. Pd on the other hand, originally known to produce CO at overpotentials above 600 mV RHE, has recently shown substantial formate FE’s at overpotentials below 200 mV. The gradual poisoning of Pd-based CO2RR electrocatalysts through the slow production of CO, even at near unity formate FEs, results in deactivation of the catalyst surface and limits the viability of Pd for sustained electrolysis.
Here, we report synthesis of core-shell nanoporous multimetallic Pd (np-PdX, where X = Co, Ni, Cu, Ag, Cu-Sn, Cu-Ti) alloys that show suppressed CO deactivation based on the subsurface composition of the alloy electrocatalysts. The Pd skinned nanoporous alloys have been obtained by electrochemical dealloying where the presence of less noble metal/alloy under the Pd shell changes the electronic structure of the Pd and consequently alters the CO adsorption strengths and subsequent catalyst deactivation. The tortuous pores (pore size: 5 – 10 nm) give rise to roughness factors above 200 which generates high geometric formate partial current densities (> 30 mA/cm2). Furthermore, the np-Pd electrodes are free standing and obviate the use of any binder and/or support which otherwise causes extra overpotential losses and morphological instability. The suppression of surface poisoning is explained on the basis of weakening of CO binding strengths due to electronic interactions of the alloying component that shifts the d-band center of Pd, as well as changes to the near surface hydrogen solubility which can also affect the adsorption strength of active/inactive intermediates and reaction selectivity.
Scanning Electrochemical Microscopy (SECM) for High-Throughput Screening of Tin Oxide Derived Catalyst Arrays for CO2 Electro-Reduction to Formate
Authors: Desilets Mayer Francis , Hosseini-Benhangi Pooya , Asselin Edouard , Gyenge Előd L. 
Published: May 2020

Formate produced from the electro-reduction of CO2 has been proposed as a safe liquid alternative to hydrogen gas in renewable energy storage schemes1 . However, catalysts for electro-reduction of CO2 to formate reaction still suffer from poor stability and activity2,3. Furthermore, the CO2 electroreduction catalysis discovery and screening process is generally hampered by slow, one catalyst sample at a time, experimental procedures. Our overall objective is to develop SECM as a reliable high-throughput technique for screening of electrocatalyst arrays. Here, using SECM, we evaluated the activity of three different tin oxide derived catalysts arranged in an array. Tin(IV) dioxide, has been previously shown to be one of the most promising catalysts for formate generation, while also being thermodynamically reduced to metallic tin at the potential at which CO2RR happens in an aqueous medium4,5. We created two different tin oxide derived catalysts by subjecting mirror-polished native tin oxide to electro-reduction at a constant potentials prior to the CO2 reduction experiments. Electro-reduction of the native tin oxide surface at -3.00 V vs. Ag/AgCl yielded a tin(IV) dioxide deficient surface covered in nanospheres (≈70 um) while electro-reduction at -1.25 V vs. Ag/AgCl create a slightly porous surface exhibiting high proportion of tin(IV) dioxide. Fine tuning the SECM technique to analyze three samples (the two electroreduced and one native tin oxide surface) in an array, we demonstrate the successful evaluation of the electrocatalytic activities of these catalysts and we discuss the advantages and challenges of using SECM to screen catalysts for CO2 reduction.
1. S. Fukuzumi, Joule, 1, 689–738 (2017) https://doi.org/10.1016/j.joule.2017.07.007.
2. C. E. Moore and E. L. Gyenge, ChemSusChem, 10, 3512–3519 (2017) http://doi.wiley.com/10.1002/cssc.201700761.
3. B. Khezri, A. C. Fisher, and M. Pumera, J. Mater. Chem. A, 5, 8230–8246 (2017) http://xlink.rsc.org/?DOI=C6TA09875D.
4. A. Dutta, A. Kuzume, M. Rahaman, S. Vesztergom, and P. Broekmann, ACS Catal., 5, 7498–7502 (2015).
5. S. Geiger, O. Kasian, A. M. Mingers, K. J. J. Mayrhofer, and S. Cherevko, Sci. Rep. (2017).

Figure 1
Atomistic Mechanisms of Single Atom Catalysis on Graphene for CO2 Reduction
Authors: Liu Yuanyue 
Published: May 2020

Single metal atoms embedded in N doped graphene have attracted extensive interest as catalysts for carbon dioxide reduction. Although DFT calculations based on computational hydrogen electrode mode have been widely used to study the atomistic mechanisms, these calculations fail to reproduce/explain some of the important experimental observations/results. Consequently, it is unclear what is the atomic structure of the active site.
We show that these problems are due to the neglect of surface charge and water molecules in the modelling, which play important roles [1,2] in electrochemistry at solid-water interface. By including these into the simulations, we can explain the experiments and identify the active site [2]. The activity is further explained in a general picture of electronic structure. [3,4]
[1] D. Kim, J. Shi, Y. Liu, JACS, 2018, 140, 9127
[2] X. Zhao, Y. Liu, in preparation
[3] Y. Liu, J. Wu, K. P. Hackenberg et al, Nature Energy, 2017, 6, 17127
[4] Y. Liu, Y. M. Wang, B. I. Yakobson, B. C. Wood, Phys. Rev. Lett. 2014, 113, 028304
Unifying Concepts in (Electro)Catalysis for Understanding the Direct Synthesis of H2O2
Authors: Kromer Matthew , Adams Jason , Zhao Yuanya , Flaherty David , Rodriguez-Lopez Joaquin 
Published: May 2020

Hydrogen peroxide (H2O2) is a sustainable and selective oxidant that is currently produced via the costly anthraquinone process from H2 and O2 gas.1,2 On-site production of H2O2 for various industrial applications would benefit from the direct synthesis of H2O2 using alternative highly selective and highly active catalysts. Recently, the mechanism of H2O2 production on metal catalysts was suggested to occur via an electron transfer between H2 and O2 mediated by individually addressable electrocatalytic steps.3 Understanding the manifestations of this electrocatalytic paradigm on (electro)catalysts would help design more selective and active H2O2 catalysts and create new opportunities for designing heterogeneous catalysts using electrochemical principles.
Here, we present an electrochemical model based on mixed potential theory for explaining and predicting the performance of H2O2 catalysts and its verification using high pressure electrochemistry, scanning electrochemical microscopy, rotating ring-disk electrode measurements, and matched electrochemical and heterogeneous catalysis reactor measurements. In our scheme, the H2 oxidation reaction (HOR) and the O2 reduction reaction (ORR) are treated as distinct half-cell reactions, allowing us to conveniently use electrochemical methods to determine reaction descriptors such as Tafel slopes and the number of electrons n transferred during the ORR. Several classes of catalysts were assessed towards their selectivity to form H2O2 via electrocatalysis and direct synthesis. Electrochemical kinetic parameters were used to obtain measures that relate the partial pressures of H2/O2 in direct synthesis to an equivalent operating potential. This operating potential was then used to predict the selectivity observed during thermochemical synthesis. We further generated guidelines to predict the characteristics of highly active catalysts.
Our model accurately predicted aspects of heterogeneous catalysis starting from purely electrochemical concepts. With the ability to directly predict H2O2 selectivities from electrochemical measurements, it is possible to rapidly screen materials to discover new low-cost and selective direct synthesis catalysts for H2O2 and for other reactions of interest. We hope the results presented here will seed new approaches for the discovery of heterogeneous catalysts using readily accessible electrochemical measurements.
1. Goor, G.; et al., 2007. Hydrogen Peroxide. Ullmann's Encyclopedia of Industrial Chemistry.
2. García-Serna, J.; et al.
Green Chem.
2014, 16, 2320–2343.
3. Wilson, N. M.; et al.
J. Am. Chem. Soc.
2016, 138, 574-586.
Electrochemical Modification of Ni-Rich Bimetallic Ni1-x Mx (M= Bi, Pd and Au) Nanoparticles for Glycerol Electro-Oxidation in Alkaline Media
Authors: Houache Mohamed S.E. , Shubair Asma , Hughesa Kara , Safari Reza , Botton Gianluigi A. , Baranova Elena A. 
Published: May 2020

Glycerol partial electro-oxidation to produce various chemicals has attracted a great amount of attention in the decade [1]. Glycerol is the main by-product of biodiesel production and could be converted into high value-added chemicals. The control of catalyst selectivity and activity could be achieved through formulation of novel, nano-structured electrocatalysts. Nickel (Ni) is an attractive material for glycerol electro-oxidation (GEOR) in alkaline media [2], due to its natural abundance, anti-poising and good stability in alkaline media. Designing inexpensive nano-structured 3D Ni electrodes could improve the catalytic activity of Ni, whereas its selectivity could be modified by adding second metal [1].
In the present work, GEOR was investigated on Ni-based mono and bi-metallic Ni x Au 1-x, Ni x Bi 1-x and Ni x Pd 1-x (x = 98, 95 and 90 at. %) nanoparticles in 1M KOH. Ni nanoparticles were synthesized by heatless chemical reduction in ethanol using sodium borohydride (NaBH4) as the reducing agent. Resulting Ni-based NPs were characterized using XRD, XPS, TEM, SEM, EDS mapping, HAADF imaging and EELS. Electrochemical measurements were carried out on Ni-based NPs using cyclic voltammetry (CV), chronoamperometry (CA) and linear sweep voltammetry (LSV) at room temperature. Results showed that Ni, NiAu and NiBi NPs are active for GEOR and that reaction proceeds through the formation of NiOOH active phase similar to bulk Ni electrodes [3]. Coupling CA with in-situ polarization modulation infrared-reflection absorption spectroscopy (PM-IRRAS) for the simultaneous analysis of products in the bulk electrolyte solution and on the Ni surface demonstrated that the main reaction products on Ni surface are glyceraldehyde, carbonyl and carboxylate ions. Whereas HPLC analysis reveals that Au, Bi and Pd adatoms strongly influence the reaction products by suppressing the pathways with C–C bond cleavage, hindering the formation of formate and enhancing the production of C2 and C3 products at different applied potentials (1.3, 1.4 and 1.55 V) and temperatures (25 and 50 oC).
The correlation of electrocatalytic activity and selectivity with nanoparticle will be discussed in terms of mass activities and product distribution during GEOR.

References

[1] M. S. E. Houache, K. Hughes, E. Baranova, Sustainable Energy & Fuels, 3 (2019) 1892-1915.
[2] M. S. E. Houache, K. Hughes, A. Ahmed, R. Safari, H. Liu, G. A. Botton, E. A. Baranova, ACS Sustainable Chemistry & Engineering, 7 (2019) 14425-14434.
[3] M. S. E. Houache, E. Cosar, S. Ntais, E. A. Baranova, J. Power Sources, 375 (2018) 310-319.
One-Pot Synthesis of Pt-Free 3D-Catalyst for PEMFC
Authors: Roiron Camille , Celle Caroline , Heitzmann Marie , Jacques Pierre-André , Simonato Jean-Pierre 
Published: May 2020

Pt-free catalysts for Oxygen Reduction Reaction (ORR) are broadly studied for Proton Exchange Membrane Fuel Cells (PEMFC) in order to widely develop hydrogen as a fuel for individual transportation. To reduce the performance gap between noble and non-noble catalysts, kinetics and thermodynamics are to be considered. The kinetics of the reaction is influenced by both the turn over frequency of the catalytic site and the density of said sites in the materials. The diffusion of gaseous reactants and liquid water produced is equally important as it modifies the thermodynamic of the reaction. For a long time now, Fe-C-N materials have been identified as the most promising Pt-free electrocatalysts for ORR despite the limited knowledge on the actual structure of the involved sites. Several approaches are currently studied to produce materials with high active site density and high porosity. Different carbon structures are modified to include active sites. The most reported and promising routes are Metal Organic Frameworks, polymers on carbon nanoparticles and silica templated organic structures.
In this new approach, carbon cryogels are chosen for their tunability and high specific surface area. Porous Fe-C-N catalysts are synthesized in one step by a modified resorcinol-formaldehyde aerogel method. Gelation, drying and pyrolysis steps are carefully studied and optimized to obtain a high density of accessible catalytic sites. The porosity of the formed materials is measured with nitrogen adsorption. Values of the Brunauer Emmett Teller (BET) surface area up to 800 m2/g are obtained. The impact of different synthesis parameters on catalytic activity is studied. To assess the catalyst’s performances toward ORR, rotating ring Disk Electrode measurements as well as Fuel Cell polarization curves will be reported.
Co-Based PGM-Free Catalysts for Oxygen Reduction in Proton-Exchange Membrane Fuel Cells
Authors: He Yanghua , Shi Qiurong , Wu Gang 
Published: May 2020

Fe-Based atomically dispersed single site catalysts are the state of the art platinum group metal (PGM)-free catalysts in proton exchange membrane fuel cells (PEMFC). However, due to the Fenton reactions potentially causing degradation of ionomers and membranes, Fe content in PGM-free catalysts must be minimized. Therefore, development low-Fe or Fe-free cathode catalysts are urgently needed for durable and inexpensive PEMFCs. Based on our previous effort to develop nitrogen‐coordinated single Co atom catalyst derived from Co‐doped metal‐organic frameworks (MOFs) [1,2], in this presentation, we will further discuss our recent effort to elucidate the formation mechanisms of CoNx sited driven by thermal treatment. Also we will introduce our new progress to prepare electronspun Co catalysts and binary CoFe catalysts for oxygen reduction in acidic electrolytes. Detailed synthesis procedure, extensive characterization, and RDE activity and fuel cell performance will be discussed.

References

(1) Wang, X. X.; Cullen, D. A.; Pan, Y.-T.; Hwang, S.; Wang, M.; Feng, Z.; Wang, J.; Engelhard, M. H.; Zhang, H.; He, Y.et al. Nitrogen-Coordinated Single Cobalt Atom Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells. Advanced Materials 2018, 30 (11), 1706758.
(2) He, Y.; Hwang, S.; Cullen, D. A.; Uddin, M. A.; Langhorst, L.; Li, B.; Karakalos, S.; Kropf, A. J.; Wegener, E. C.; Sokolowski, J.et al. Highly active atomically dispersed CoN4 fuel cell cathode catalysts derived from surfactant-assisted MOFs: carbon-shell confinement strategy. Energy & Environmental Science 2019, 12 (1), 250.
Microbial Biocathode Catalyzing Oxygen Reduction and Processing Nitrification
Authors: Barrière Frédéric , Flinois Thomas 
Published: May 2020

Oxygen biocathodes with electroactive biofilms on graphite electrodes were developed consistently and reproducibly from wastewater inoculum under a high ammonium content selective pressure in a batch microbial fuel cell configuration using ferrocyanide at the anode. The microbial biocathodes process nitrification reactions and catalyse the reduction of molecular oxygen with an onset potential of 0.0 V vs. Ag /AgCl, and a current density at -0.28 V of j = -296 μA/cm2 at pH 7 and 20 °C under oxygen saturation (Cf. Figure).These biofilms also reduce hydrogen peroxide (not shown) at +0.25 V, the potential of an electroactive species in the biofilm (Cf. Figure). The nitrification reactions performed by the biofilm are found to be associated with the catalytic reduction of dioxygen. Nitrification reactions were studied by assaying the nitrogen species (ammonium, nitrite and nitrate) and the effect of adding hydroxylamine, an intermediate of the enzymatic oxidation of ammonium. Metagenomic studies via 16S rRNA gene sequencing of the biofilms onto the colonized electrodes were performed 4 week after inoculation. These studies show that the cathodic biofilms were significantly enriched with Cupriavidus, a proteobacteria genus, that is likely to be responsible for the catalytic properties of the microbial biocathode.
The Figure shows the reduction of molecular oxygen by a colonized electrode at pH 7 and 20 °C in a 0.1 M fresh phosphate buffer as recorded with slow scan rate cyclic voltammetry. Scan rate: 1 mV/s. Green: abiotic graphite electrode under oxygen saturation. Black: biocathode under argon saturation. Red: biocathode under air. Blue: biocathode under oxygen saturation. Note also the chemically reversible system found at +0.25 V and assigned to the biofilm. Catalytic hydrogen peroxide reduction (not shown) occurs at the potential of this system.

Figure 1
(Invited) Structural Characterization of Nanoporous Materials Via Gas Sorption
Authors: Cychosz Struckhoff Katie 
Published: May 2020

Recently, much effort has been devoted to the development of nanoporous materials which exhibit hierarchical pore structure with the appropriate balance of micro- and mesopores, as well as advantageous pore connectivity. The network of interconnected micro- and mesopores facilitates efficient transfer of fluids to and from active sites within and through the material, leading to benefits in numerous applications. Detailed insights into the pore architecture (pore size distribution, pore volume, and pore interconnectivity) are important because they control transport phenomena, diffusional rates, and govern selectivity.
Gas sorption is well suited for this because it assesses a wide range of pore sizes, spanning the entire micro- and mesopore range. Additionally, an in-depth characterization of the pore network can also be obtained with a detailed understanding of the adsorption and phase behavior of fluids confined in such complex pore structures. Here, we discuss recommended experimental and state-of-the-art data reduction methods for a comprehensive study of the pore architecture of nanoporous materials which includes: choice of adsorptive, accurate BET area calculation, DFT for pore size and volume determination, hysteresis scanning, and interpretation of material phase transitions.
Recent examples of the structural characterization of novel carbons, mesoporous zeolites, and MOFs will be discussed.
FIB/SEM Nanotomography of a CO2 Electrolyzer Cathode Catalyst Layer
Authors: McLaughlin David , Thiele Simon 
Published: May 2020

Silver catalysts have demonstrated selective reduction of CO2 to CO. CO produced by this reaction could replace fossil fuel derived CO as a feedstock for fuels and value added chemicals. Furthermore, gas diffusion electrodes based on silver catalyst have additionally achieved high current density. Thus, the foundation for development of this promising defossilization strategy has been laid. In order to implement this strategy it is necessary to optimize catalyst layers to improve their durability and efficiency. At the same time, current density and selectivity need to be maintained. Detailed understanding of the electrodes is necessary to achieve these goals. In particular, the wetting parameters and the delicate balance of molecular and ionic transport needs to be investigated. We posit that in analogy to fuel cells, resolving the catalyst layers is essential.
Tomographic reconstructions have successfully resolved the catalyst layers of fuel cells and water electrolyzers down to the nanoscale. So far, CO2 reduction gas diffusion electrodes have been imaged using X-Ray microtomography. However, the applied X-ray tomography was insufficient in resolving the nano-porous structure of these catalyst layers. We have reconstructed a porous silver catalyst layer using focused ion beam scanning electron microscope (FIB/SEM) tomography. It is thus possible to resolve the pores down to the nanoscale. Using the geometric representation, obtained from the reconstruction, we calculated geometric structure and mass transport parameters. Finally, we modeled the effect of (partial) flooding of the catalyst layer. We present the tomography alongside results for the porosities, diffusivities and conductivities of the catalyst layer.
Overcoming the Selectivity-Permeability Trade-Off with Nanoporous Carbon Nanotube Membranes
Authors: Chen Chiatai , Li Yifan , Meshot Eric R. , Buchsbaum Steven F. , Herbert Myles , Zhu Rong , Kulikov Oleg , McDonald Ben , Bui Ngoc , Jue Melinda L. , Park Sei Jin , Valdez Carlos A. , Hok Saphon , Doona Christopher J. , Wu Kuang Jen , Swager Timothy M. , Fornasiero Francesco 
Published: May 2020

From energy storage to separation applications, performances of nanoporous membranes are typically limited by an inherent trade-off between transport rate and selectivity. For example, conventional protective garments sacrifice breathability to prevent exposure to harmful agents, and this trade-off severely hinders the duration of their active use. The discovery of enhanced fluid flow in single-walled carbon nanotubes (SWCNT) has provided a path toward combining the diametric properties of high selectivity and permeability into a single SWCNT-based material, yet successful demonstration of this promise remains elusive.
Using as example the design of novel materials for protective clothing applications, herein we demonstrate a smart, nanoporous, SWCNT membrane that overcomes the limitation of conventional protective garments. Specifically, we show that the adoption of nanometer-wide SWCNTs for ultrafast moisture conduction [1] enables a simultaneous boost in size-sieving selectivity and water-vapor permeability by decreasing nanotube diameter, thereby overcoming the breathability/protection trade-off [2].Our membrane platform can rapidly and selectively transition from a highly breathable state in a safe environment to a protective state when exposed to a chemical threat. Dynamic response to chemical stimuli is achieved through the physical collapse of an ultrathin copolymer layer on the membrane surface, which efficiently gates transport through the SWCNT membrane pores [2].Multifunctional SWCNT membranes such these present exciting opportunities in many other areas including energy-efficient separations, energy storage, and smart delivery.

References

1. N. Bui, E. R. Meshot, S. Kim, J. Peña, P. W. Gibson, K. J. Wu, F. Fornasiero, Adv. Mater., 28 (2016) 5871.
2. Y. Li, C. Chen, E. R. Meshot, S. F. Buchsbaum, M. Herbert, R. Zhu, O. Kulikov, B McDonald, N. Bui, M. L. Jue, S. J. Park, C. Valdez, S. Hok, C. J. Doona, K. J. Wu, T. M. Swager, F. Fornasiero, submitted (2019)
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.