bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Co-Doping Strategy for Enhanced Photoelectrochemical Water Splitting Performan
Authors: Jang Ji-Hyun
Published: December 2020

Titanium and heteroatom-codoped hematite photoanodes showed significantly increased photoelectrochemical (PEC) water splitting activity. The Ti and heteroatom co-doping in hematite not only suppresses the number of metal ions that cause electron hole pair (EHP) recombination at the hematite surface but also generates an internal electric field for easy hole extraction. The co-doped hematite converted the incident photons to EHPs with much reduced recombination and exhibited an excellent photocurrent density of greater than 2.5 mA/cm2 at 1.23 VRHE. Our co-doping strategy provides a straightforward way of addressing the chronic short-hole diffusion length issue that causes a high electron hole recombination rate, to potentially improve the performance of PEC devices.
(Invited) Extended Electrochemical Potential Range Induced By Plasmonic Electronic Excitation
Authors: Murakoshi Kei
Published: December 2020

Spectroelectrochemistry is powerful tool to investigate electronic sates and geometrical structures of electrified interfaces in-situ under the conditions where photonic and electronic energy conversion functionalities emerge. One can use plasmon-powered processes to expand the ability of the spectroscopy regarding sensitivities in space, time, and energy resolutions. As their characteristics on localization of surface plasmons into molecule scale, huge intensity gradient of electromagnetic field would break the limit of light-matter interactions via the modification of the selection rule of the electronic excitation process. I have discussed about the possibility for the surface-enhanced-Raman scattering (SERS) as the probe to monitor the exotic electronic excitation processes[1-8]. Based on the observation of a small number of molecules at the plasmonic metal nanostructures by SERS, possibilities leading to the future innovative photo-functionalities were demonstrated by showing improved properties at optical manipulation of electrons and molecules, and ions. In this presentation, we will show that the localized surface plasmons of the Au nanodimer structures prepared on defect-free graphene provide highly-confined electromagnetic field to generate holes and electrons of the electrochemical potentials beyond the limit of far field light illumination [7]. Novel non-zero wavevector excitation results in the generation of highly reductive and oxidative powers for electrochemical reactions. The present findings point to a novel approach to breaking the limit of opto-electronic interactions and photochemical reactions using various materials.

References

[1] K. Murakoshi and L. M. Liz-Marzán et al., ACS nano, 14, 28-117 (2019).

[2] T. Konishi et al., J. Am. Chem. Soc. 135, 1009-1014 (2013).

[3] F. Nagasawa et al., J. Phys. Chem. Lett. 5, 14-19 (2014).

[4] M. Takase et al., Nature Photonics, 7, 550-554 (2013)

[5] H. Minamimoto et al., Faraday Discuss. 205, 261-269 (2017).

[6] F. Kato et al., ACS Photonics 5, 788-796 (2018).

[7] J. Zhang et al., Nano Lett. 19, 7887-7894 (2019).

[8] K. Suzuki and X. Li et al., ACS Energy Lett. 5, 1252-1259 (2020).
(Invited) Photoelectrochemical Hydrogen Generation Derived from Water Dissociation Under Supercontinuum Solar Light (25)
Authors: Sakamaki Kenji , Honda Yume , Kobayashi Yumena , Yoshida Rina , Hiruta Erika , Ootomo Ryusei
Published: December 2020

We created a two-compartment cell (2CC) separated by a bipolar membrane (BPM1) sandwiched between through-holed electrodes (THEs) assembly (BPMTHEA-2CC) based on the Golden Role for sustainable water splitting derived from water dissociation (WD) with a dual chemical bias (CB).2-4 The BPMTHEA-2CC provides an infinite supply of active reaction species, H+ and OH-, from water with an opposite bidirectional charge separation under appropriate applied voltage conditions. We have achieved hydrogen generation derived from WD with BPMTHEA-2CC using an oxygen evolving reaction active TH dimensionally stable anode (De Nora Permelec Ltd) prepared on Pt gauze. Liberated gas was analyzed using a gas chromatograph equipped with a MS-5A column and a thermal conductive detector (TCD). We succeeded in detecting appropriate amounts of molecular hydrogen generated in the cathode of a large-sized BPMTHEA-2CC, anolyte (water)|TH anode|BPM|TH cathode|catholyte (water), by imposing a voltage with less than the theoretical 1.23 V for water splitting at room temperature. We disprove the theory of water electrolysis established for hundreds of years. However, we still require external voltage for water electrolysis. Instead of external voltage, we have harnessed supercontinuum solar light throughout by designing optical tandem, wavelength multiplexing. Zero-bias photocurrent was observed by applying TH n-type semiconductor photoanodes to BPMTHEA-2CC. WD at the junction of BPM is considered to be originated in second Wien effect. Thus Au nanoparticle (Au-NP) was introduced into the junction of BPM to carry out plasmon-induced (PI) WD. With mixing different sizes of Au NPs, a wide range of absorption wavelengths would be attainable. Preliminary results obtained using Au-NP modified BPMTHEA-2CC were reported with two plausible mechanisms.3 A simple 4-port chamber has been developed to measure hydrogen concentrations down to 7.5 ppm and was used to demonstrate PEC zero bias hydrogen generation with harnessing supercontinuum solar light.

V. J. Frilette, J. Phys. Chem.,
60, 435 (1956).

K. Sakamaki et al., AST2019, June 2-5, 2019, Awaji Yumebutai, Japan, O-24 (2019).

K. Sakamaki et al., 236th ECS Meeting, Oct. 13-17, 2019, Atlanta, GA, USA, I04-1896 (2019).

K. Sakamaki et al.,
J. Applied Electrochem. 49, 949-962 (2019). https://doi.org/10.1007/s10800-019-01337-8

Figure 1
(Invited) Ligands in Electroreduction of CO2: N-Heterocyclic Carbene-Capped Polymers to Promote Catalytic Efficiency
Authors: He Jie
Published: December 2020

N-heterocyclic carbenes (NHCs) are excellent ligands that bind to a variety of transition metals with extremely high binding strength via σ donation. In my talk, I will highlight the use of two polymeric N-heterocyclic carbenes (NHC) (polydentate and monodentate) to stabilize metal nanocatalysts (Au and Pd) for efficient CO2 electroreduction in aqueous solution. Compared with other conventional ligands including thiols and amines, metal-carbene bonds are stable under reductive potentials prevent the nanoclustering of nanoparticles, which is of key importance for any practical application. In particular, Au nanocatalysts modified by polymeric NHC ligands show an activity retention of 86% after CO2 reduction at -0.9 V for 11 h, while it is less than 10% for unmodified Au. We demonstrate that the hydrophobicity of polymer ligands and the enriched surface electron density of metal NPs through σ-donation of NHCs substantially improve the selectivity for CO2 reduction over proton reduction. As a passive coating on the surface of metal nanocatalysts, carbene-terminated polymers can control the accessibility of substrates, i.e., CO2 vs. H2O, as a means to improve the Faradic efficiency toward CO2 reduction. Our results provide guideline to improve catalytic efficiency and stability of metal nanocatalysts for CO2 electroreduction and, more generally, as cathodic materials for other electroreduction reactions.
Electrolytic Reduction of Bicarbonate into CO
Authors: Berlinguette Curtis P. , Li Tengfei , Lees Eric W. , Goldman Maxwell , Salvatore Danielle A. , Weekes David M.
Published: December 2020

Electrolyzers designed to convert CO2 into carbon products typically rely on a gaseous CO2 feedstock or CO2-saturated electrolyte. We show herein that aqueous HCO3- solutions can also be electrochemically converted into CO gas at meaningful rates in a flow cell containing a bipolar membrane (BPM) and a silver catalyst on a carbon support. Electrolysis upon a N2-saturated 3.0-M KHCO3 solution yields CO with a faradaic efficiency that is comparable to analogous experiment where the bicarbonate solution is saturated with gaseous CO2. This electrolytic process is made possible by reaction of protons, delivered by the BPM, with bicarbonate to form electrocatalytically active CO2. This reaction pathway offers the potential to use electrolysis to bypass the thermally-intensive step of extracting CO2 from HCO3- solutions generated in carbon capture schemes.
(Invited) Operando Characterization of Electrocatalysts and Semiconductor/Electrocatalyst Interfaces in Water-Splitting Devices
Authors: Boettcher Shannon W.
Published: December 2020

Electrocatalysts, particularly for the oxygen evolution reaction, are dynamic systems that evolve during operation with composition, structure, and morphology changing. These processes can have dramatic effects on electrocatalytic activity, electrical properties, and the electronic interfaces that form when electrocatalysts are deposited on semiconductors in solar photochemical architectures. I will discuss recent work from our team applying operando atomic force microscopy, x-ray absorption microscopy, and a suite of electrochemical techniques to understand this dynamic behavior. I will also describe new efforts to interrogate the properties of electrocatalyst/semiconductor interfaces under operating conditions with nanoscale resolution using potential-sensing atomic force microscopy.
Neutrons for Battery Research (in-situ and operando studies): An Overview
Authors: Gilles Ralph , Gasteiger Hubert A. , Gernhäuser Roman , Hattendorff Johannes , Jossen Andreas , Märkisch Bastian , Révay Zsolt , Seidlmayer Stefan , Trunk Markus , Werner Lukas , Weydanz Wolfgang
Published: December 2020

The further development of battery materials and cells must go hand in hand with improved in-situ and operando characterization methods. Such techniques provide a better and deeper understanding of the mechanisms to determine even minor changes in cell components and their impact on the overall performance of cells and their capacity or battery life.

The last ten years there has been a great deal of interest in scattering techniques for examining battery components and in particular complete cells [1]. Neutrons as a probe or techniques derived from neutrons play a special role in this development because their unique properties and possibilities are very well suited for battery research. On the one hand, neutrons can penetrate deep into materials and on the other hand, they are very sensitive to light elements as Li, H or N. In addition, neutron methods are non-destructive, which makes it possible to measure the inner part of a cell as well as to perform operando measurements. Improvements of neutron instrumentation including coatings of neutron guides, higher counting rates of detector systems and dedicated sample environments. Further the higher neutron flux of modern neutron large scale facilities accelerate the development of neutrons for battery research. In-situ and operando studies while changing external parameters such as charging/discharging or temperature change etc. are carried out to examine cells under real working conditions.

Neutron diffraction, small-angle neutron scattering, neutron imaging and neutron depth profiling are considered among the most suitable methods for battery research. This contribution presents typical applications of these different neutron methods, which are used on different length scales. Neutron diffraction and small-angle neutron scattering are suitable to investigate changes from the atomic scale up to the mesoscopic scale (~ 300 nm). Processes such as Li intercalation in graphite anodes during battery charging can be described in detail [2,3]. Neutron imaging is suitable to follow in-situ the electrolyte filling process in hard case cells [4]. The neutron depth profiling technique is applied for studies of the Lithium mobility at the different electrode interfaces to determine the Li concentration profile in approximately the first 50 mm [5], e.g. the SEI layer [6].

Reference
s
:

[1] R. Gilles, Journal of Surface and Investigations: X-ray, Synchrotron and Neutron Techniques (2020), in print.

[2] V. Zinth et al., Journal of Power Sources 361 (2017) 54-60.

[3] J. Hattendorff et al., J. Appl. Cryst. (2020), 53, 210-221.

[4] W. J. Weydanz et al., Journal of Power Sources 380 (2018) 126-134.

[5] M. Trunk et al., Materials Characterization (2018), 146, 127-134.

[6] S. Whitney et al., Journal of the Electrochemistry Society (2009), 156(11) A886.
Electrolyte Transfer at a Liquid-Solid Polypyrrole Interface Quantified By in Situ X-Ray Reflectometry
Authors: Lakner Pirmin Hubert , Brinker Manuel , Huber Patrick , Keller Thomas Florian
Published: December 2020

In situ characterization of the electrochemical (EC) intercalation mechanism of ions in conductive polymer films is one of the most important aspects in the development of novel organic supercapacitors. Compared to atomic force microscopy and quartz microbalance measurements, synchrotron-based in situ X-ray reflectometry (XRR) allows deeper and more detailed insights into electrically controlled transfer processes of electrolytes across liquid-solid interfaces. The low roughness of the layer system to be investigated, which is required for XRR, is a particular challenge: Electrochemically deposited polypyrrole (PPy) films naturally possess a rough surface, the typical cauliflower structure. In the present study, PPy was deposited on a silicon crystal with a fast-varying voltage to obtain a PPy film with a very smooth surface, which led in parallel to a significantly denser film, which also increases the XRR contrast. This 30 nm thin PPy film was measured in situ in a 0.1M HClO4 environment with XRR at different voltage levels between -0.2 and +0.5V vs Ag/AgCl and the film thickness and electron density were determined. A linear and reversible change in thickness and electron density was measured, which is typical for the potential-dependent intercalation process of anions. The number of electrons transferred across the electrolyte-PPy interface was determined from the change in thickness and electron density, from which the transport of matter was derived. The correlation with the electrically measured transferred charge resulted in a ratio that was significantly below the expected value for exclusive anion exchange. Considering all present and available matter, it can be deduced that proton transport partially compensates for the charge and that 2-3 water molecules per incorporated perchlorate anion are removed from the film. Fast XRR measurements on the same PPy film during applied cyclovoltammetry showed two intervals of different behavior of the PPy film: In the higher voltage range anion intercalation dominates, the PPy film shows a very high pseudo-capacity due to its high density, while in the lower voltage range proton exchange starts and reduces the pseudo-capacity. Electrochemical impedance spectroscopy confirmed these results: Above the transition of these two voltage ranges, the conductivity of the PPy film increases dramatically due to the intercalation of perchlorate anions. With the presented synchrotron-based, in situ EC-XRR setup the film thickness, the electron density, and the change of both, as well as the pseudo-capacitance and conductivity as a function of the applied voltage can be measured simultaneously on ultra-thin electrochemical polymer films. Especially for the development of new electrochemical systems this is a highly potent measurement technique for in situ characterization.
Quantitative Concentration Mapping with AFM-SECM
Authors: Mirabal Alex , Calabrese Barton Scott
Published: December 2020

Efficient transport of reaction intermediates between active sites can improve the efficiency of multi-site reactions.1–3 Experimental detection of these nanometer length scale transport mechanisms is enabled by Scanning Electrochemical Microscopy (SECM). Electrochemical measurements can allow for concentration profile mapping to elucidate the transport processes in experimental systems. SECM can correlate position dependent responses to properties of the system. There is a significant impact on the response profile due to the SECM tip’s presence at the nanoscale. Finite Element Analysis (FEA) has been used to understand and remove these in situ tip effects.

The calculated concentration, using current-flux relations, can be complex near sites generating flux through reactions and/or transport. Additionally, uncertainties such as tip positioning in relation to the interface site can further complicate the response. Quantitative concentration fields can more readily be interpreted through FEA, by matching the experimental tip response.

Electrodeposited platinum nanoparticles were imaged topographically and electrochemically with a Bruker AFM-SECM (Figure 1). The positive response over the nanoparticles vs. the planar HOPG sites allows for kinetic response imaging. The model is parameterized through approach curves and verified though SECM mapping correlation.

We have previously applied FEA to correlate experimental in situ results to in operando conditions through a non-linear regression of approach curve responses. Here, we use this approach to generate corrected concentration profiles. We use Pt nanoparticle catalysts deposited on HOPG, to develop surface property correlations. In this way, a comparison can be drawn between in situ and in operando approaches.

References

(1) Schuhmann, W. Amperometric Enzyme Biosensors Based on Optimised Electron-Transfer Pathways and Non-Manual Immobilisation Procedures. Rev. Mol. Biotechnol. 2002, 82 (4), 425–441.

(2) Wheeldon, I.; Minteer, S. D.; Banta, S.; Barton, S. C.; Atanassov, P.; Sigman, M. Substrate Channelling as an Approach to Cascade Reactions. Nat. Chem. 2016, 8 (4), 299–309.

(3) Liu, Y.; Hickey, D. P.; Guo, J. Y.; Earl, E.; Abdellaoui, S.; Milton, R. D.; Sigman, M. S.; Minteer, S. D.; Calabrese Barton, S. Substrate Channeling in an Artificial Metabolon: A Molecular Dynamics Blueprint for an Experimental Peptide Bridge. ACS Catal. 2017, 7 (4), 2486–2493.

Figure 1
Scanning Electrochemical Cell Microscopy; Measurement Process Optimization to the Electrochemical Response Based on Experimental Parameters
Authors: Cho Sang-Joon , Kim Seong‐Oh , Goo Kyo-Suk , Kang Jihoon
Published: December 2020

As the development of scanning probe microscopy (SPM) continues, the spatial resolution and sensitivity for various material properties steadily improve. Therefore, SPM images morphological features as well as electrical, mechanical, magnetic, and chemical properties with a nanoscale resolution. Among the various SPM techniques, pipette-based SPM offers new possibilities and insights into the sample’s electrochemical properties. Since the invention of scanning electrochemical microscopy (SECM), the first-generation pipette-based SPM for electrochemical measurement, it has been extensively used in many research fields, e.g. for visualizing chemical reactions at surfaces and interfaces. However, the difficult distance control between the pipette probe and the sample surface limits the application of SECM.

Here, we introduce scanning electrochemical cell microscopy (SECCM): a latest pipette-based SPM method, which investigates electrochemical responses on target materials in a point-by-point approach using the ionic current for distance control. We present experimental and theoretical data on contributing factors to the electrochemical response, including pipette configuration, redox species, scan rate and choice of substrate. A variety of pipette inner diameters (range from ~150 nm to ~ 1 μm), buffer concentrations, and voltammetric sweep rates are reviewed using well-defined conductive substrates and electrodes. Based on our results, we propose optimized experimental parameters for various measurement conditions. We believe that SECCM has great potential in providing new insights to electrochemical properties of surfaces and interfaces required for research on chemical energy storage, among others.

Figure 1
(Keynote) Mechanistic Studies of the Electrochemical CO2 Reduction on Single Site, Metallic and Hybrid Electrocatalysts
Authors: Strasser Peter
Published: December 2020

The science and technology of the direct electrochemical CO2 reduction reaction on both model-type solid catalytic surfaces and Gas Diffusion Electrodes (GDEs) inside electrolyzers offer as many formidable challenges as intriguing opportunities. Controlling the selectivity (faradaic efficiency), while maximizing the energy efficiency by lowering the kinetic overpotentials remains key to turn this complex reaction into a practical process embedded in a process chain. To achieve this, deeper mechanistic understanding of surface catalytic reaction pathways by means of time-resolved kinetic characterization of the production rates of major and minor reaction products is needed.

In this talk, I will highlight some of our recent advances in the understanding of the chemical mechanism of the direct electrochemical reduction of CO2 and of related mixed feeds into value-added fuels and chemicals on metallic surfaces, on non-metallic, single metal-site electrocatalysts, and on metallic/non-metallic tandem catalyst schemes. Apart from in situ X-ray analytical techniques, focus was placed on new insights using time-resolved Differential Electrochemical Mass Spectrometry (DEMS) conducted in capillary inlet flow cells. These studies enable milli-second resolved analysis of reaction products under stationary and transient conditions, and thus provide access to accurate onset potentials of reaction products. Computational mechanistic predictions are tested by experiments and plausible reaction pathways and intermediates and their binding is discussed. Metallic catalysts comprise Cu and Cu-based alloys, while non-metallic single site catalysts include high surface-area solid carbons with atomically dispersed, nitrogen-coordinated metal atom moieties.
(Invited) Hybrid Mixed-Metal-Oxide-Based Catalytic Systems for Efficient Electroreduction of Carbon Dioxide
Authors: Rutkowska Iwona , Kulesza Pawel
Published: December 2020

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties. There has been growing interest in the electrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large over-potentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the electrochemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.

We explore here the ability of polynuclear inorganic metal oxo systems to stabilize and derivatize metal and carbon nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, molybdenum or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ru), thus affecting their chemisorptive and catalytic properties. Metal oxide (WO3, MoO3, TiO2) nanospecies can generate –OH groups at electrocatalytic interface.

Our electrocatalytic results with copper-substituted polytungstates (or polyoxometallate-network-stabilized copper oxo assemblies)and with copper nanostructures over-coated with WO3 or MoO3 nanostructures imply improved selectivity toward CO2-reduction relative to the competitive hydrogen evolution as well as lower tendency of copper sites to undergo poisoning. We believe that the partially reduced WO3 or MoO3 are capable of sorption of hydrogen, or shifting the proton discharge toward more negative potentials, rather than inducing hydrogen evolution.
(Keynote) Electrodeposited Catalysts for High Efficiency CO2 Electrolyzers
Authors: Chen Xinyi S. , Gewirth Andrew A.
Published: December 2020

This talk addresses the reactivity associated with CO2 reduction. Electrodeposition of metals from plating baths containing 3,5-diamino-1,2,4-triazole (DAT) as an inhibitor yields highly porous materials exhibiting enhanced activity for electrochemical reactions. Electrodeposition of CuAg or CuSn alloy films from such plating baths yields high surface area catalysts for the active and selective electroreduction of CO2 to multi-carbon hydrocarbons and oxygenates. Alloy films containing Sn exhibit greater efficiency for CO production relative to either Cu along or CuAg at low overpotentials. In-situ Raman and electroanalysis studies suggest the origin of the high selectivity towards C2 products to be a combined effect of the enhanced stabilization of the Cu2O overlayer and the optimal availability of the CO intermediate due to the Ag or Sn incorporated in the alloy. Sn-containing films exhibit less Cu2O relative to either the Ag-containing or neat Cu films, likely due to the increased oxophilicity of the admixed Sn.

In order to further control surface oxygen content we developed a copper-polyamine hybrid catalyst that significantly increases the selectivity for ethylene production. The Faradaic efficiency for ethylene production is 87% ± 3% at -0.47 V versus reversible hydrogen electrode, with a full-cell energetic efficiency reaching 50% ± 2%. Raman measurements indicate that the polyamine entrained on the Cu electrode results in higher surface pH, higher CO content, and more stabilized intermediates relative to entrainment of additives containing little or no amine functionality. This work shows that polymer incorporation can install functional groups onto an electrode surface, alter surface reactivity, and lead to enhanced product selectivity.
Electrochemical Pumping Behavior of an Anion Exchange Membrane CO2 Separation Device
Authors: Muroyama Alexander Paul , Patru Alexandra , Pribyl Bernhard , Gubler Lorenz
Published: December 2020

Anion exchange membranes (AEM) are well studied in the context of fuel cells and water electrolyzers, as they permit the use of non-noble catalysts. However, such alkaline systems have a notable drawback of carbonation when they are operated using atmospheric air, which is known to reduce the anion conductivity of the membrane. The (bi)-carbonate ions are removed from the membrane through the migration of hydroxide ions, also known as the self-purging mechanism. This carbonation effect of AEMs can be utilized to selectively remove CO2 from a dilute gas mixture (e.g., flue gas or air) and transport it across the membrane, as shown in Figure 1.

Effective CO2 transport across the membrane can be enabled using hydrogen evolution and oxidation reactions in the presence of CO2 and alkaline media. This methodology differentiates itself from other membrane-based separation techniques, as it allows for low concentrations (<1%) of CO2 to be removed at a high fraction (>90%) from a gas stream. Significant developments are required to optimize such a system, reduce material costs and cell overpotentials, and allow for long-term operation.

We performed preliminary experiments proving the concept of an electrochemical CO2 separation device utilising AEMs. Steady-state galvanostatic experiments with on-line non-dispersive infrared gas analysis have demonstrated the clear relationship between current density, cell potential, and CO2 pumped across the membrane for a wide range of inlet CO2 concentrations. Faradaic efficiencies for CO2 transport are strongly dependent on the inlet CO2 concentration and current density. Considerations for further development are discussed.

Figure Caption: Schematic of AEM CO2 separator

Figure 1
(Keynote) Enhancing CO2 Electroreduction to Oxygenates
Authors: Yeo Boon Siang Jason
Published: December 2020

A fundamental question in the electrochemical CO2 reduction reaction is how to rationally control its catalytic selectivity, for example, how to convert CO2 to hydrocarbons or oxygenates. In this presentation, we shall share our latest work on this theme to make multi-carbon oxygenates such as ethanol, propanol, etc. We shall illustrate this with several examples. One of them is by creating highly defective Cu sites. The other is by adding a CO-producing metal like Ag to Cu. We found that the CuAg boundaries in the composites facilitate the coupling of carbon-containing species to give ethanol. Specifically, oxide-derived Cu nanowires mixed with 20 nm Ag particles reduce CO2 to ethanol with a current density of -4.1 mA/cm2 at -1.1 V vs. RHE and ethanol/ethylene Faradaic efficiency ratio of 1.1. These figures of merit are respectively 5 and 3 times higher than those for pure oxide-derived Cu nanowires. Extensive experimentations and DFT calculations shows selective ethanol evolution via Langmuir-Hinshelwood *CO + *CHx (x = 1, 2) coupling at CuAg boundaries. The formation of energy-intensive CO dimers can be circumvented.
(Invited) Electrochemical Treatment of Aquaculture Wastewater and Water for Irrigation in Off-Grid Locations
Authors: Greenlee Lauren Fay , Qing Geletu , Foster Shelby L , Anari Zahra , Thoma Greg , Matlock Marty , Low Todd
Published: December 2020

The use of electrochemical processes and technology has been a focus for the energy conversion and storage fields, as technologies ranging from batteries to fuel cells and electrolyzers have received significant attention as cutting-edge and advanced next-generation technologies. To date, the application and development of electrochemical technologies for water and wastewater treatment needs have been limited to specific niches; for example, electrochemical technology has been a focus for non-membrane-based desalination (e.g., electrodialysis or capacitive deionization) and for electrocoagulation of metals and organics, as a replacement for chemically-driven coagulation. However, electrochemical processes and technologies offer a much greater range of possibilities for wastewater treatment needs and goals. From chemical-free disinfection to electrocatalytic conversion of contaminants to recovery of critical nutrients, electrode engineering, control of operational voltage and current windows, and optimization of device design can all be used to address key problems in wastewater treatment. In our research group, we focus the use of electrochemical approaches to address the removal of key contaminants and enable a chemical-free disinfection step for remote and rural wastewater treatment needs in the agriculture and aquaculture sectors. In this talk, I will discuss our ongoing work and recent results on electrochemical approach, electrode engineering, electrochemistry experiments, and device development for the off-grid treatment of aquaculture wastewater for the goals of ammonia removal and disinfection, as well as the off-grid treatment of surface water for irrigation uses, where the goal is on-demand disinfection. Electrochemistry studies for aquaculture wastewater treatment using graphite and graphite-supported PtRu films as the anode demonstrate that the presence of PtRu reduces the voltage required for ammonia oxidation. When graphite is used as the cathode, the disinfectant molecule hydrogen peroxide is produced, suggesting electrochemical disinfection is possible in parallel with ammonia oxidation. In addition, the electrode configuration can be used to generate chlorine on demand, providing an alternate route for disinfection. For both water scenarios, we investigate the roles of electrode type, electrochemical operating parameters, and water chemistry parameters. In addition, our research has included several field site studies to demonstrate performance of our flow electrochemical cells for natural water samples.
Sunlight Driven Desalination Coupled with Wastewater Treatment and Hydrogen Production
Authors: Kim Seonghun , Han Dong Suk , Park Hyunwoong
Published: December 2020

A novel sunlight-water-energy nexus technology is presented that combines the photoelectrocatalytic (PEC) desalination of saline water and desalination-driven wastewater remediation coupled with the production of molecular hydrogen (H2) from water. To accomplish this, morphologically tailored TiO2 nanorod (TNR) and hydrogen-treated TNR (H-TNR) array photoanodes are placed in an anode cell and Pt foils are located in a cathode cell, while a middle cell containing saline water (0.17 M NaCl) faces these cells through anion and cation exchange membranes, respectively. Upon irradiation by simulated sunlight (AM 1.5G, 100 mW×cm-2), the photogeneration of charge carriers initiates the transport of chloride and sodium in the middle cell to the anode and cathode cells, respectively, leading to the desalination of saline water. The chloride in the anode cell is converted to reactive chlorine species (RCS), which effectively decompose urea to N2 as a primary product (>80%), while the sodium in the cathode cell accelerates the H2 production from water with a Faradaic efficiency of ~80%. The PEC performance of the H-TNR photoanodes is superior to that of the TNR in the anodic and cathodic processes because of the reduced charge transfer resistance and sub-nanosecond charge transfer kinetics (~0.19 ns), leading to a specific energy consumption of 4.4 kWh×m-3 for 50% desalination, with an energy recovery of ~0.8 kWh×m-3. The hybrid system is found to operate for a period of ~60 h with natural seawater, and virtually all the photoanodes are shown to be capable of driving the hybrid process. Although tested as a proof-of-concept, the present technology opens up a novel field involving a sunlight-water-energy nexus, promising high efficiency desalination and the desalination-driven remediation of water with simultaneous H2 production
Development of Carbon Fiber-Based Ni(OH)2 Electrode for Application in Urea Wastewater Treatment/Hydrogen Production
Authors: Hung Chi-Han , Liu Yi-Hung
Published: December 2020

Introduction

Urea-containing wastewater is discharged every day from factories, agricultural fertilizers, and human/animal urine, etc. If we do not properly teat it in time, it will cause environmental pollution, health hazards and other problems. Conversely, treating urea-containing wastewater can produce H2 energy source through an electrolysis process [1], which is considered attractive due to its lower electrolysis voltage than that for water splitting. In the past, nickel hydroxide (Ni(OH)2) has been used as a catalyst material for urea oxidation reaction (UOR), because it has several advantages such as cheap and good catalytic effect on urea. However, UOR performance is still not satisfied due to poor material design for electrodes, and thus needs to be improved. In light of this, our research is committed to developing a composite electrode integrating Ni(OH)2, carbon nanotubes (CNTs), and carbon fibers (CFs). The electrode allows to enhance UOR performance, which can simultaneously benefit urea degradation and H2 production.

Experimental

CFs were used as the electrode substrate, and Ni(OH)2 were deposited on the CFs surface together with carbon nanotubes (CNTs), through a one-step electrophoretic co-deposition method. Afterward, the composite was further experienced a hydrothermal reaction to complete the fabrication of the Ni(OH)2/CNT/CF electrode. SEM, XRD, Raman spectroscopy, and TGA were used to examine the material properties of the composite electrode. A three-electrode electrolytic system composed of the composite electrode, a Pt counter electrode, and a Ag/AgCl reference electrode was set up to treat the urea-containing wastewater. During the treatment, cyclic voltammetry and linear sweep voltammetry were applied to investigate the Ni(II)/Ni(III) redox reaction and UOR. Details about the electrode kinetics were also discussed.

Results and Discussion

The experimental results show that the Ni(OH)2/CNT/CF electrode has more favorable UOR performance compared to the Ni(OH)2/CF and CF ones. In addition, the α-Ni(OH)2-phase catalyst is found to present better electrocatalytic activity than the β-Ni(OH)2-phase catalyst. This could be due to larger d spacing of (001) plane in α-Ni(OH)2, allowing more inserted water molecules than those in β-Ni(OH)2. Accordingly, it expedites ion transport between the Ni(OH)2 sheets and repeated Ni(II)/Ni(III) transformation during continuous UOR [2], corresponding to better electrochemical performance. On the other hand, doping CNTs is found to benefit the increased reaction area and electrical conduction of the composite electrode. As a result, the required overpotential for UOR is reduced and the reversibility of Ni(II)/Ni(III) redox reaction is improved, leading to more efficient UOR.

References

[1] B. K. Boggs, R. L. King and G. G. Botte, Chem. Commun., 32, 4859–4861 (2009).

[2] C. Lin, Z. Gao, F. Zhang, J. Yang, B. Liu and J. Jin, J. Mater. Chem. A, 6, 13867–13873 (2018).
Photo-Electro Catalysis for Reduction of Halogenated Disinfection By-Products and Mechanism of H+/H• Confined Transfer and Transformation
Authors: Dai Yunrong , Liu Shuang , Duan Cunxu , Yin Lifeng
Published: December 2020

Halogenated disinfection by-products (HDBPs) produced during the traditional disinfection process are bringing potential water quality safety risks due to nerve, reproductive, and genetic toxicity. In this study, the graphene oxide (GO) coated photo-electrode with strong charge carriers separation capacity was prepared for the dehalogenation and detoxification of HDBPs in aqueous solution. Under the irradiation of xenon lamp with bias voltage less than 0.25 V, parachlormetaxylenol (PCMX), methenyl trichloride and dichloroacetic acid were found to be readily dehalogenated and decomposed over GO coated TiO2, WS2, MoS, and C3N4 in aqueous solution. Especially, the dehalogenation efficiency of HDBPs on GO coated TiO2 was higher than that on the other GO coated semiconductors. Based on the simulation and characterization, the transfer/conversion mechanism of proton (H+) and hydrogen (H•) in the confinement space of GO coated semiconductor interface was proposed, and the dehalogenation and detoxification mechanism of HDBPs under the attack of H• was also evidenced based on the in-site surficial analysis.
Study of Hydrogen Thermal Treatment IrxTa1-XOy/Nano-TiO2 Catalyzing Ammonium
Authors: Wang Miao
Published: December 2020

With the rapid development of the industrialization process in the world, wastewater's inorganic nitrogen concentration could not be ignored simply. Composite semiconductor materials have been used for many years in electrocatalysis, Titanium dioxide, a semiconductor, is an inactive oxygen evolution electrocatalyst because of its low conductivity and poor reactivity. This study prepared three-electrode configuration, which.represents double-layered nanoparticle titania electrocatalyst (Ti / IrxTa1-xOy / nano-TiO2; denoted as n-TEC) as anode and platinum foil as cathode. The main anodic reactions are the formation of chlorine and decomposition of Ammonia. Through EPMA, SEM, XRD, XPS, EPR, Raman etc., combine with electrochemical test on anode cell (mediate the decomposition of ammonia and electrocatalytic oxidations of chloride), respectively. Hence stability and durability of electrocatalyst materials are major challenges that need to be optimized, hundreds hours of catalytical experiment has been prepared, characterization of the electrodes was compared before and after experiment as well. On the basis of original electrode (raw n-TEC), we did hydrogen thermal treatment. The electrodes show great differences under different retreatment conditions, free chlorine’s faraday efficiency promoted by 6%, which leads to a discussion of the effect of oxygen vacancies on the material. Conductivity should be taken into consideration with electrochemical impedance spectroscopy (EIS) test, after hydrogen thermal treatment charge transfer resistance has been increased 46%. In view of the influence of different constituent materials on electrochemical or electrocatalytic properties, new sights for the engineering and other aspacts of electrochemical are provided.
Electrochemical Desalination System Accompanying Wastewater Treatment and CO2 Reduction Reaction
Authors: Kim Byeong-ju , Park Hyunwoong
Published: December 2020

The configuration of the hybrid electrochemical desalination system with ion exchange membranes is presented. Ion exchange memebranes (anion exchange membrane, cation exchange membrane) was alternately inserted into the system chambers and induce electrochemical desalination with transport of anions and cations toward the anode (nano-TiO2) and cathode (Bi-foam), respectively. Simultaneously, reactive chlorine species (RCS) was produced with the anodic reaction of chloride ion supplied by its transport from the desalination chamber. the produced reactive chlorine species initiated decomposition reaction of urea in anolyte. the Bi-foam cathode converted the dissolved carbon dioxide into formate, the simplest carboxylate anion with one carbon atom. the Faradaic efficiency of formate production was >95%. Additionally, small solar panel (0.5 x 3.5 cm2, 4 V) was wired to examine the solar-to-formate energy efficiency of the hybrid electrochemical desalination system. More details of experiment results will be presented and discussed.
Electrochemical Oxidation of Guanines of DNA Loaded on Carbon Nanomaterials
Authors: Kim Jinheung
Published: December 2020

Investigating the interactions of biomolecules DNA/RNA with carbon nanomaterials is very important for applications in bioassay and bioanalysis. Graphene and graphene oxide (GO) and carbon nanotube have been successfully adopted by exploiting the binding affinity difference between single-stranded oligonucleotides (ssDNA) and double-stranded oligonucleotides (dsDNA) to graphene sheets. In this work, we describe the electrochemical DNA oxidation with [Ru(bpy)3]2+ to understand the interaction between dsDNA (and corresponding ssDNA) and reduced graphene oxide (rGO). The electrochemical oxidation rate of guanine bases of ssDNA bound to rGO by electrochemically generated [Ru(bpy)3]3+ was much slower than that unbound to rGO. Our study revealed that ssDNA constrained on rGO was significantly protected from the electron transfer to [Ru(bpy)3]3+ because of π,π-stacking interaction between nucleobases and rGO. On the other hand, the oxidation rates of 11-, 20-, and 27-mer dsDNA bound to rGO increased relative to those of dsDNA alone, demonstrating that the guanine bases of dsDNA on interacting with rGO became more accessible to [Ru(bpy)3]3+. Our electrochemical data illustrated that dsDNA could be totally or partially dehybridized and bind to rGO to form ssDNA/rGO. Furthermore, absorption, circular dichroism spectra, and fluorescence measurements of ethidium bromide using ssDNA and dsDNA with rGO supported the dehybridization of dsDNA in the presence of rGO and CNT.
Optical Trapping Raman Spectroscopy As a Sensor / Actuator / Treatment System
Authors: Bertz Morten , Molinnus Denise , Schoening Michael J. , Homma Takayuki
Published: December 2020

In recent years, Raman spectroscopy has evolved into a broadly used analytical method in chemistry, life sciences, and medicine. Here, we combine Raman spectroscopy with optical trapping and optical microscopy to isolate and investigate individual micron-size biological particles from a sample. In this setup, Raman spectroscopy provides a label-free chemical fingerprint while light microscopy reveals the sample morphology. In addition, elastic light scattering as well as observation of diffusive movement in the optical trap’s potential offer information on particle size and refractive index. Single particles can be captured and manipulated for tens of minutes. During this time, the stably trapped particles can be exposed to a variety of chemical and physical stimuli such as heat, light of different wavelengths, or changes in the chemical composition of the particle environment through microfluidics (Fig. 1A).

In this work, we employ this optical trapping Raman spectroscopy sensor / actuator / treatment system to study the effect of hydrogen peroxide (H2O2) on individual spores of Bacillus atrophaeus, an important model system to assess the efficacy of industrial sterilization processes. Interestingly, we find B. atrophaeus spores to be stable for more than 30 minutes while optically trapped even at elevated temperatures (> 70 °C). Exposure to H2O2 results in spore degradation in a concentration-dependent manner within several minutes and is accelerated by high temperatures. Raman spectroscopy indicates that spore degradation is characterized by the rupture of the spore core resulting in the fast release of dipicolinic acid, a major spore biomarker that is considered key for spore resistance to environmental stress (Fig. 1B). Oxidative degradation of the spore shell starts before core rupture and continues after dipicolinic acid release. Simultaneous observation of spore morphology corroborates this two-phase model. Illumination with shorter (< 550 nm) wavelength light exposes the spores to oxidative stress via the generation of reactive oxygen species in the spore environment by light, thereby mimicking the H2O2 sterilization process. In the presence of small amounts (0.5%) H2O2, spore lifetime is reduced to several seconds.

With the presented system, we address spore activity down to the single cellular level in a multimodal manner: trapping and manipulation of single spores over several tens of minutes (actuator functionality), stimulation of single spores by temperature, illumination, and H2O2 exposure (treatment functionality) as well as on-line monitoring of spore activity (sensor functionality).

Figure 1