bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Keynote) Tuning the Selectivity of CO2 Electroreduction through Dynamic Catalyst Transformations Under Reaction Conditions
Authors: Roldan Cuenya Beatriz 
Published: December 2020

The utilization of fossil fuels as the main energy source gives rise to serious environmental issues, including global warming caused by the continuously increasing level of atmospheric CO2. Recently, the electrochemical conversion of CO2 (CO2RR) to chemicals and fuels driven by electricity derived from renewable energy has been recognized as a promising strategy towards sustainable energy.
In my talk I will provide examples of recent advances in the development of highly active size- and shape-controlled nanoparticle (NP) electrocatalysts (Cu, Cu-Zn, Cu-Ag) and how their structure (crystal orientation, atomic arrangement, size, shape, defects), oxidation state and composition influence their selectivity in CO2RR. I will also discuss how important morphological motives and chemical sites can be created and regenerated in pulsed electrochemistry experiments. Additionally, the determining role of the electrolyte in the surface restructuring, reaction activity and selectivity will be illustrated. Finally, the importance of in situ and operando characterization methods (e.g. EC-AFM, Liquid-TEM, XAS, XPS, XRD, LEEM/XPEEM) to gain in depth understanding on the structure- and electrolyte-sensitivity of real CO2RR catalysts under working conditions will be demonstrated. Our results are expected to open up new routes for the reutilization of CO2 through its direct selective conversion into higher value products such as ethylene and ethanol.
(Invited) Electrodeposition of Manganese Oxides Utilizing Hydrothermal Electrochemical Technique
Authors: Yamaguchi Akira , Otsubo Yoshiki , Kitadai Norio , Nakamura Ryuhei , Miyauchi Masahiro 
Published: December 2020

Hydrothermal electrochemistry can conduct electrochemical experiments under high temperature and pressure conditions and is one of the useful methods to fabricate size-controllable and highly crystalline materials. Although this technique has been applied to electrodeposition of metal oxides like BaTiO3 (Yoshimura et al., Jpn. J. Appl. Phys., 28, L2007, 1989), precise control and examination of electrochemical process was hard to be achieved in previous reactors because they adopted two-electrode systems. Moreover, reaction pressure was determined by temperature, so it is difficult to discuss their specific contribution to the electrochemical process.
Recently, we have developed hydrothermal electrochemical reactor in which three-electrode system was adopted in order to control and monitor the electrochemical process precisely. This system also achieves independent control of temperature and pressure so that we can discuss their contributions to the final products. Here in this work, we attempted to fabricate Manganese oxide thin film with electrodeposition technique under different temperature and pressure, and examined their electrochemical water oxidation activity. Manganese oxides are prepared in industry with electrodeposition technique, so they are good candidates as model compounds to examine the property of our home-made hydrothermal electrochemical reactor.
MnO2 was deposited on Ti substrate with galvanostatic condition of 10 mA /cm2 for 20 min utilizing 0.5 M MnSO4 / 0.2 M H2SO4 aqueous solution as a precursor. Based on XRD analysis, all deposited samples were ε-MnO2. When we increase deposition temperature, XRD peaks got sharpen, indicating the crystallinity increased. SEM observation clarified their morphological difference. Namely, MnO2 deposited at 160℃ possessed needle-like structure, while spherical structure was observed for sample deposited at 100℃. To examine the effect of pressure on deposition products, we conducted electrodeposition under different pressure from 0.1 to 4 MPa while maintaining temperature at 100℃. As a result, XRD peaks were slightly shifted depending on pressure. This means lattice constant is controllable by regulating deposition pressure.
Their electrochemical water oxidation activity also demonstrated the advantage of hydrothermal electrodeposition compared with conventional technique. After annealing at 200℃, 160℃-electrodeposited sample exhibited superior activity to 100℃-deposited sample. Although the elucidation of the reason for higher catalytic activity is future work, those results indicate our hydrothermal electrochemical technique is widely applicable to material synthesis such as metal oxides, metal sulfides, and so on.

Figure 1
Assessing pH and Voltage Effects on the Binding of CO to Model Copper Catalyst Surfaces Via a DFT-Continuum Theory
Authors: Weitzner Stephen Eric , Akhade Sneha A , Varley Joel Basile , Wood Brandon C. , Baker Sarah E , Duoss Eric B , Otani Minoru 
Published: December 2020

The electrochemical conversion of CO2 to commodity products such as hydrocarbons and oxygenates is an attractive approach for generating non-fossil derived chemical and fuel stocks and for the storage of energy in chemical bonds. To date, a number of studies have shown that the activity and selectivity of copper-based catalysts for the CO2 reduction reaction towards valuable higher order carbon products are highly sensitive to the local reaction environment. Furthermore, the local electrolyte concentration and local pH is intimately tied to the applied voltage and the mass transport of reactants and products within the interfacial region. In recognition of this, several recent efforts focused on engineering the design of electrochemical reactors to reduce mass transport limitations indicate a pronounced effect on the apparent selectivity of the copper catalyst. While these efforts have highlighted a new direction for improving the efficiency of the CO2 reduction reaction, the rational design of these reactors remains challenging due to the need to optimize features of the reactor across multiple time and length scales. In this talk, we will discuss recent efforts within our laboratory to address the influence of the local pH on the CO2 reduction reaction at the atomistic level. We focus the discussion on the binding of CO, a key reaction intermediate in the CO2 reduction pathway, whose preferential hydrogenation or dimerization leads to the production of C1 and C2 products, respectively. We additionally demonstrate how the use of hybrid approaches employing density functional theory (DFT) and continuum models can help bridge time and length scales within the context of atomistic CO2 electroreduction modeling.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Effects of Gas Diffusion Layers on a CO2 electrolysis Cell with an Anion Exchange Membrane for Ethylene Production
Authors: Kudo Yuki , Tamura Jun , Yamagiwa Masakazu , Kitagawa Ryota 
Published: December 2020

The concept of an electrolysis system, where CO2 is converted into hydrocarbons using renewable electricity, has been attracting much attention because it is expected to be one solution to achieve a decarbonized society. In order to realize an economical electrolysis system, it is important to produce high-value products such as ethylene with high reaction rate (i.e. the operating current density of CO2 electrolysis), and high efficiency (low operation voltage).
The anion exchange membrane (AEM) CO2 electrolysis cells using gas diffusion electrodes (GDEs) are more advantageous than the traditional flow cell using a solution purged with CO2, both in terms of higher current density and lower voltage operation. This is because of the efficient CO2 reduction occurring at the three-phase interface of a GDE (i.e. CO2 is directly fed to the vicinity of the electrocatalysts though a gas diffusion layer (GDL)), increasing the current density, and of the cell electrodes being closely spaced, lowering the voltage. However, there are only several studies of the AEM CO2 electrolysis cells for high rate of ethylene production [1].
Here, we investigate ethylene production performance of an AEM CO2 electrolysis cell consisting of copper and copper oxide nanoparticles coated on GDL as a cathode, iridium oxide-coated titanium support as an anode, and an AEM. Among these components, the GDL can play a crucial role in the efficient transport of CO2 and water management, therefore we focus on understanding the effects of GDL properties such as thickness, porosity and density on ethylene production. We evaluated the electroreduction characteristics of the cells under ambient condition by a constant current method in which a constant current is supplied for a period of time. The faradaic efficiency (FE) and partial current density (PCD) of gas products such as ethylene, carbon monoxide, methane and hydrogen are examined as a function of the total current densities (TCD). We found that the FEs and PCDs depended on the density and the thickness of the GDLs. The low density and thick GDL showed high FE and PCD of ethylene due to high gas diffusibility. The FE and the PCD of ethylene at the TCD of 600 mA/cm2 reached a maximum of 50 % and 300 mA/cm2, respectively.
References
[1] Christine M. Gabardo, Colin P. O’Brien, Jonathan P. Edwards, Christopher McCallum, Yi Xu, Cao-Thang Dinh, Jun Li, Edward H. Sargent, and David Sinton, Joule 3, 1–15, November 20, 2019
Interplay between Mesoscale Architecture and Catalytic Output in CO2 Gas-Diffusion Electrolyzers
Authors: Raciti David , Braun Trevor Michael , Xu Heng , Cruz Mutya A. , Wiley Benjamin J. , Moffat Thomas P. 
Published: December 2020

With the anticipated effects of global climate change upon us, induced by egregious CO2 emissions, it is imperative to implement technologies to close the carbon cycle. One potential technique to do this is storing the energy from intermittent sources (e.g. solar, wind, hydro) in the form of chemical bonds, such as the electrochemical reduction of CO2. By reducing CO2 to energetically and chemically useful products of CO2 (i.e. CO and C2H4) we can both reduce reliance on fossil fuels and mitigate atmospheric CO2 levels. However, controlling the selectivity towards which particular product is formed and preventing the parasitic hydrogen evolution reaction (HER) is a crucial challenge that must be overcome.1 Exploring fundamental mechanisms and new catalyst materials to overcome this challenge, can be skewed due to the low diffusivity (≈2x10-9 m2/s)2 of CO2 in the liquid phase causing inefficient utilization of catalyst active sites. Unlike the oxygen reduction reaction, use of a rotating disc electrode does not resolve the issue due to the competitive HER reaction. Therefore, it becomes imperative to study physical structure-function relations (e.g. catalyst layer thickness) in a cell that provides ample flux of solely CO2, such as a gas-diffusion electrolyzer (GDE) which greatly increases the diffusivity of CO2 and gas products by enabling transport through gas channels (≈1.6x10-5 m2/s). By filtering nanowires through a gas-diffusion electrode (Figure 1 a-b) we fabricated electrodes of varying thicknesses that were then applied as catalysts in a gas-diffusion electrolyzer (Figure 1c). Results show that even under high CO2 flux conditions there is an interplay between selectivity (Figure 1d), activity (Figure 1e) and catalyst layer thickness. Further exploration of this interplay in commercially relevant electrolyzers can expedite optimized implementation of catalysts in the industrial sector and hopefully aid in solving the global climate crisis at hand.
(1) Verma, S.; Kim, B.; Jhong, H.-R. “Molly”; Ma, S.; Kenis, P. J. A. A Gross-Margin Model for Defining Technoeconomic Benchmarks in the Electroreduction of CO2. ChemSusChem
2016, 9 (15), 1972–1979. https://doi.org/10.1002/cssc.201600394.
(2) Raciti, D.; Mao, M.; Ha Park, J.; Wang, C. Mass Transfer Effects in CO 2 Reduction on Cu Nanowire Electrocatalysts. Catalysis Science & Technology
2018, 8 (9), 2364–2369. https://doi.org/10.1039/C8CY00372F.
Figure 1: Electron microscopy images of Ag nanowires (a) top-down and (b) cross-section, on a gas-diffusion electrode. This electrode is than applied as a CO2 reduction catalyst in a (c) gas-diffusion electrolyzer. The thickness of the Ag nanowire catalyst layer influences both the (d) selectivity and (e) mass activity of the reaction.

Figure 1
Electroreduction of CO2 on Modified Graphene Supported Sn Nanoparticles in Half-Cell and Full Cell Configuration
Authors: Bera Bapi , Aaron Douglas , Mench Matthew M 
Published: December 2020

Electrochemical reduction of CO2 is a process that can reduce carbon dioxide from the atmosphere and simultaneously produce useful, value-added chemicals, specifically solar fuel [1]. Depending on the catalyst materials, CO2 can be reduced to single carbon or multi carbon products [2]. Sn nanoparticle was used to catalyze CO2 reduction to produce formate in alkaline medium. Sn nanoparticles were synthesized by the sol-gel method with different precursors at room temperature and supported with carbon black and conductive graphene nano-sheets. Graphene nano-sheets were synthesized by the conventional modified Hammer method [3]. X-ray diffraction (XRD) and transmission electron microscope (TEM) enabled insights into phase formation, shape, and size of the Sn nanoparticles. Reference materials included commercial Sn nanoparticles with carbon support (Sn:C_com), commercial Sn nanoparticles with graphene support (Sn:GN_com), Sn nanoparticle synthesised using Sn (II) 2-ethylhexanoate and Sn (II) chloride as tin precursor with carbon support as respectively (Sn:C_Tin-2-hexa) and (Sn:C_SnCl2). Three-electrode chronoamperometry showed that Sn:GN_com enabled high CO2 electrolysis current density (see Figure 1(a)). Electrochemical impedance spectroscopy (EIS) of the prepared catalysts in CO2-saturated 0.1 M KHCO3 was recorded in a three-electrode rotating disk electrode (RDE) configuration (see Figure 1(b)). The charge-transfer resistance was smallest for Sn:GN_com sample, as well. CO2 reduction was performed in a full electrochemical cell using the same architecture as a low temperature polymer electrolyte fuel cell (PEFC) in alkaline medium with anion exchange membrane. Polarization plots show a unique feature (two different slopes); this change in slope is dominated by a distinct change in the area specific resistance (ASR) value (see Figure 1(c)).
In this work, we mainly focus on the CO2 electroreduction to produce formate in a full cell with RDE (rotating disc electrode) measurements providing additional insights into catalytic properties. Our primary goal is to understand the basic underlying physical processes during CO2 reduction in the full cell set up and also find inexpensive and efficient catalytic active materials for the reduction process.

Figure 1: CO2 electrolysis (a) and impedance spectra (b) in RDE configuration with different catalyst. (c) Polarisation plots for CO2 reduction in full cell configuration with different flow rate

References:

Wang, C. Niu, and D. Wang, Journal of Colloid and Interface Science 527 (2018) 95–106.

Zhao, and J. Wang, Chemical Engineering Journal 293 (2016) 161–170.

C.-T. Hsieh, and W.-Y. Chen, Surface & Coatings Technology 205 (2011) 4554–4561.

Figure 1
(Invited) Structural and Mechanistic Details on the Oxygen Evolution Reaction on Nife Layered Double Hydroxide and Ni(OH)2
Authors: Dionigi Fabio , Ferreira de Araujo Jorge , Merzdorf Thomas , Strasser Peter 
Published: December 2020

The incorporation of Fe3+ ions in Ni(OH)2 is responsible for a dramatic oxygen evolution reaction (OER) activity enhancement.1 NiFe based (oxy)hydroxides are among the most active electrocatalysts for the OER in alkaline electrolytes.2 Their crystal structure, known as layered double hydroxide (LDH), is composed of layers of edge sharing metal oxygen octahedra that are intercalated with water molecules and charge balancing anions (Figure 1).3 In contrast, Fe-free Ni(OH)2 can be synthesized in the well defined brucite-like crystal structure, which does not have intercalated species and is indicated as β-M(OH)2. Oxidative deprotonation and possibly the electrocatalytic OER reaction lead to reversible structural changes that are only observable with in operando or in situ methods.1, 4 Several reports investigated the oxidized phases, but key aspects of the catalytically OER active site remain elusive and more investigations are necessary.
In this contribution our results obtained using in operando wide angle X-ray scattering (WAXS) on crystalline NiFe LDH nanostructured catalysts and β-Ni(OH)2 catalysts will be presented.5 We identified the structure of the active catalyst state and observed that the lattice spacing under operating conditions changes reaching a similar value for both catalysts (Figure 1). Using a unique differential electrochemical mass spectrometry (DEMS) apparatus and isotope labelled experiments we further unravel mechanistic details on how the OER mechanism proceeds on these catalysts.
References

D. Friebel, M. W. Louie, M. Bajdich, K. E. Sanwald, Y. Cai, A. M. Wise, M. J. Cheng, D. Sokaras, T. C. Weng, R. Alonso-Mori, R. C. Davis, J. R. Bargar, J. K. Norskov, A. Nilsson and A. T. Bell, J Am Chem Soc, 2015, 137, 1305-1313.

M. Gong, Y. G. Li, H. L. Wang, Y. Y. Liang, J. Z. Wu, J. G. Zhou, J. Wang, T. Regier, F. Wei and H. J. Dai, J Am Chem Soc, 2013, 135, 8452-8455.

F. Dionigi and P. Strasser, Advanced Energy Materials, 2016, 6.

M. Gorlin, J. F. de Araujo, H. Schmies, D. Bernsmeier, S. Dresp, M. Gliech, Z. Jusys, P. Chernev, R. Kraehnert, H. Dau and P. Strasser, J Am Chem Soc, 2017, 139, 2070-2082.

F. Dionigi, Z. Zeng, I. Sinev, T. Merzdorf, S. Deshpande, M. B. Lopez, S. Kunze, I. Zegkinoglou, H. Sarodnik, D. X. Fan, A. Bergmann, J. Drnec, J. F. De Araujo, M. Gliech, D. Teschner, J. Greeley, B. Roldan Cuenya and P. Strasser, submitted 2019.

Figure 1. Shift of the (003) diffraction peak associated to the interlayer distance for NiFe LDH catalysts between the resting state (black) and OER active state (red).5 3D structural model of the as prepared NiFe LDH.

Figure 1
(Invited) Electrochemical Extraction and Conversion of CO2 from Seawater
Authors: Digdaya Ibadillah A. , Sullivan Ian , Lin Meng , Han Lihao , Cheng WenHui , Atwater Harry A. , Xiang Chengxiang("CX") 
Published: December 2020

Capture and conversion of CO2 from anthropogenic emission is becoming an increasingly important social responsibility as the concentration of atmospheric CO2 continues to rise above record high levels. To achieve carbon negative conditions in the long term, capture and extraction of CO2 directly from air and seawater will likely play a much bigger role. The concentration of the present CO2 in the atmosphere is ~400 ppm, or 0.00079 kg m−3. As a result, a large volume of air needs to be processed in direct air capture processes. In contrast, world ocean constitutes the largest carbon sink, absorbing about 40% of anthropogenic CO2 since the beginning of industrial era with an effective CO2 concentration of 2.1 mmol kg−1, or 0.095 kg m−3 in seawater, which is a factor of 120 times larger than in the atmosphere. Thus, extraction of CO2 from seawater provides an alternative and unique approach in the global carbon removal technological landscape.
Herein, a new bipolar membrane electrodialysis (BPMED) cell design, in which the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at the electrodes were replaced with reversible redox couple reactions with minimal thermodynamic and kinetic voltage losses, was designed, constructed and evaluated. At an operating current density of 3.3 mA cm−2, and a seawater flow rate of 37 ml min−1, a record low electrochemical energy consumption of 155.4 kJ mol−1 or 0.98 kWh kg−1 of CO2 was achieved. The demonstrated BPMED cell also exhibited a high CO2 extraction efficiency of 71% of total dissolved inorganic carbon (DIC). We also demonstrated, for the first time, the direct coupling between the CO2 extraction from seawater via BPMED and electrochemical CO2 reduction (CO2R) into fuels and chemicals. The outlet CO2 stream from the BPMED was fed into tandem custom-built vapor-fed GDE cells to first perform the oxygen reduction reaction (ORR) using a nanoparticle Ag-based catalyst followed by CO2R using Cu or Ag as the electrocatalyst. This configuration allowed us to convert CO2 from seawater to fuels and valuable chemicals such as carbon monoxide, ethylene, ethanol, and propanol with total Faradaic efficiency (FE) of up to 73% at current densities of 58 mA cm−2 using CO2R Cu electrocatalyst and to carbon monoxide with selectivity of up to 95% at current densities of 11.15 mA cm−2 using CO2R Ag electrocatalyst.

Figure 1
Pd Shape-Controlled Nanoparticles Decorated with Metals for Electrochemical Nitrate and Nitrite Reduction
Authors: Lim Jeonghoon , Park Jinho , Lee Seung Woo , Hatzell Marta C. 
Published: December 2020

Nitrate (NO3
-) pollution of groundwater occurs due to anthropogenic activities such as the overuse of nitrogen-rich agriculture fertilizers. Furthermore, nitrite (NO2
-) causes adverse effects on human health such as methemoglobinemia (“blue baby syndrome”) and cancer. Currently, physicochemical technologies such as reverse osmosis or ion exchange are used for nitrate removal, but these approaches are not sustainable as waste disposal of the brines remains a critical challenge (requiring the use of expensive post-treatment processes). Electrochemical NO3
- remediation; however, offers several advantages when compared to physiochemical approaches for nitrate removal as NO3
- is directly converted to harmless dinitrogen (N2) gas resulting in no waste production. The main challenge with electrochemical NO3
- reduction is the low activity and selectivity of the NO3
- to N2. The activity is limited by the rate-determining step (NO3(ads)
- to NO2(ads)
-), and selectivity is determined by the reduction of NO2(ads)
-to N2 and/or ammonium (NH4
+).
To achieve an efficient activity and selectivity for the electrochemical denitrification, we develop Pd shape-controlled nanoparticles and introduce secondary metals on the surface of Pd electrocatalysts by chemical reduction methods. The decorated metals promote the reduction of NO3
- to NO2
- (rate determining step) and the Pd facets enhances the selectivity of NO2
- to N2. Rotating ring disk electrode (RRDE) tests enabled the measurement of improved activity and selectivity of NO3
- to N2 using shape-controlled Pd that contain surface modifications (metal atoms). This study demonstrates that electrochemical nitrate reduction is an important approach to reduce environmental impacts associated with removing NO3
- from water.