bluuebunny/crossref_metadata_2025_split huggingface dataset:
Voltammetric Study and Electrodeposition of Zinc from Room Temperature Ionic Liquid 1-Butyl-1-Methylpyrrolidinium Bis((trifluoromethyl)Sulfonyl)Imide
Authors: Chen Po-Yu , Wang Yu-Sheng 
Published: February 2020

Voltammetric behavior of Zn(II) introduced into the room temperature ionic liquid 1-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide (RTIL BMP-TFSI) via the addition of ZnCl2 or Zn(TFSI)2 salt was studied. It is surprised that ZnCl2 is highly soluble in this IL because many transition metal chlorides are insoluble in the TFSI-based ILs, leading to the retardation of applying the RTIL BMP-TFSI to electrodeposition. Two redox couples both associated to the redox reaction Zn(II) + 2e− ↔ Zn were observed in the ZnCl2 solution, which resulted from the nonchloride-coordinated and chloride-coordinated Zn(II) species, respectively. However, a single redox couple corresponding to Zn(II) + 2e− ↔ Zn was observed in the Zn(TFSI)2 solution (Figure 1). According to the experiments of voltammetric titration, it was supposed that TFSI anions exhibit much stronger coordinating ability towards Zn2+ ions than to other common transition metal ions, resulting in the high solubility of ZnCl2 in BMP-TFSI. A sufficient amount of chloride anion must be introduced in order to observe the chloride-coordinated Zn(II) species in the Zn(TFSI)2 solution. Afterwards, TFSI anions coordinated to Zn2+ ions were gradually replaced by chloride ions continuously introduced into the Zn(TFSI)2 solution. Finally, no zinc redox couple could be observed once Zn2+ions were completely coordinated with chloride ions.
Electrodeposition of Zn was achieved by potentiostatic electrolysis using copper substrates as the electrodes from the IL containing ZnCl2 and Zn(TFSI)2, respectively. Crystalline Zn could be obtained from the two different solutions. The crystallinity and surface morphology of the Zn electrodeposits depended on the applied potentials, and nanostructured Zn could be obtained at some particular electrodepositing potentials. An interesting current-vibration behavior was observed during the potentiostatic electrodeposition of Zn from ZnCl2 solution, and this vibration behavior obviously depended on the applied potentials. It was supposed that the current-vibration behavior was due to a chloride-releasing & chloride-combination mechanism accompanied with the diffusion-drove supplementary of electroactive Zn(II) species because the vibration phenomenon was only observed while the applied potentials were set at where the chloride-coordinated Zn(II) species was reduced in the ZnCl2 solution.

Figure 1
Nitrogen-Doped Hollow Carbon Spheres As a Sensitive Electrochemical Sensor for Simultaneous Determination of Pb (II) and Hg (II)
Authors: Liu Shantang 
Published: February 2020

Keywords: Electrochemical sensor; Hollow Carbon Spheres; Anodic stripping voltammetry (ASV); Heavy metal ions.
Heavy metal ions (HMIs) pose a detrimental risk to human health and environment due to their higher toxicity [1]. Among those ions, both mercury and lead are the well-known toxic and relatively widespread water pollutants that could damage to the brain, heart, kidneys, lungs, and the immune system [2]. The electrochemical method as a promising and elegant technique has been widely used for trace detecting of HMIs due to the excellent sensitivity, low cost, short analysis time, and easy portability [3-4].
We fabricated a nanostructured nitrogen-doped hollow carbon spheres (N-HCSs), which was a kind of modified carbon nanomaterials and used in HMIs detection with enhanced performance for the first time. As-prepared N-HCSs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption and desorption analysis, X-ray photoelectron spectroscopy (XPS). Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. Under optimized conditions, the anodic stripping voltammetric performance toward HMIs were evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detailed study of the enhancing electrochemical response in stripping voltammetry for the individual and simultaneous detection of ultratrace Pb2+ and Hg2+ in drinking water was described. The detection limits achieved (15 nM and 2.35 nM for Pb2+ and Hg2+) are much lower than the guideline values in drinking water given by the World Health Organization (WHO)[5]. In addition, an interesting phenomenon of mutual interference between Pb2+ and Hg2+was observed. When the concentration of Pb is fixed, the sensitivity to Hg lowers a little and the response current of Pd doesn't change with the increasing concentration of Hg. Meanwhile, when the concentration of Hg is fixed, the sensitivity to Pb lowers a little and the response current of Hg does increase with the increasing concentration of Pb. This study provides a novel nitrogen-decorated hollow spheres carbon-based material for the construction of sensitive electrochemical sensors that meet the needs of environmental control.

References

[1] L. Wang, W. H. Xu, R. Yang, T. Zhou, D. Hou, X. Zheng, J. H. Liu, X. J. Huang, Anal. Chem.2013, 85, 3984.
[2] L. Zhou, W. Xiong, S. T. Liu, J. Mater. Sci.2015, 50, 769.
[3] W. Xiong, L. Zhou, S. T. Liu, Chem. Eng. J.2016, 284, 650.
[4] Q. Guan, W. Xiong, L. Zhou, S. T. Liu, Electroanalysis. DOI: 10.1002/elan.201500481.
[5] R. X. Xu, X. Y. Yu, C. Gao, Y. J. Jiang, D. D. Han, J. H. Liu, X. J. Huang, Anal. Chim. Acta. 2013, 790, 31.

Figure 1
Toward Proper Understanding of the Nature of the Active Sites in Non-PGM Catalysts and the Redox Mechanism for ORR
Authors: Jia Qingying , Li Jingkun , Mukerjee Sanjeev 
Published: February 2020

Developing efficient catalysts based on inexpensive and abundant materials for the sluggish oxygen reduction reaction (ORR) constitutes one of the grand challenges in the fabrication of commercially viable fuel cell devices and metal–air batteries for future energy applications. Despite recent advances in developing active and durable non-platinum group metal catalysts as promising alternatives to Pt, a less empirical synthesis approach is still missing due to the lack of proper understanding of the mechanistic origin of the ORR and the underlying surface properties under working conditions that govern catalytic activity.
Here, by employing in situ x-ray absorption spectroscopy (XAS) together with complementary characterization techniques such as Mössbauer spectroscopy etc., we propose that the distorted Fe2+-N4-Cx moiety, in which the central Fe2+ ion is located out of the N4-plane and at low spin state without the fifth axial ligand, is the active site responsible for the high ORR activity of pyrolyzed Fe-based catalysts. The local structure of this active site under ex situ conditions is drastically different from that obtained under working conditions, and is thus disconnected from the ORR activity. In situ XAS studies further reveal that the ORR is mediated by the reversible Fe2+/3+ redox transitions with potential-dependent population of active sites.1 Accordingly, the high ORR activity of the distorted Fe2+-N4-Cx moiety is attributable to the out-of-plane Fe displacement with low spin state, which leads to high Fe2+/3+ redox transition potential that minimizes the site-blocking effect at the targeted potential, as well as appropriate number of eg-electrons that favors O2 adsorption.

Figure 1
Molybdenum Sulfide Films By Atomic Layer Deposition As Electrocatalysts in Hydrogen Evolution Reaction
Authors: Shin Hyunjung 
Published: February 2020

Control of the amounts of exposed edge sites of molybdenum disulfide (MoS2) is the key to develop the efficient catalyst for hydrogen evolution reaction (HER). Atomic layer deposition (ALD) method has been well-known for conformal coating of desired materials. However, application of ALD to control the amount of edge site of MoS2 remains exclusive. Here, we demonstrate that ALD was successfully applied to grow MoS2 films together with control the amount of edge sites and high porous morphology. Our data show that the non-ideal mode of ALD growth on planar surfaces could be used in controlling the relative fractions of active-edge sites of MoS2. In addition, the effect of amount of edge sites to the Tafel slopes and current densities in HER performance was also investigated. We achieved the best catalytic performance of the current densities up to 20 mA cm-2 at -0.3 V versus reversible hydrogen electrode, Tafel slope of 50 to 60 mV/decade, and onset potential of 143 mV vs RHE. Our results are indicative for the first time that ALD approach is a potential strategy in designing HER materials.
Heterojunction Electrode Designed for Saline Wastewater Electrolysis
Authors: Yang Yang , Hoffmann Michael R 
Published: February 2020

Electrochemical oxidation is a promising candidate for decentralized wastewater treatment, due to its modular design, convenient operation, and small carbon footprint. In this process, pollutants are oxidized at the anode, while valuable hydrogen is produced at the cathode. Different from water splitting, the ideal anodes in EO process should have high activity toward oxidant generation rather than oxygen evolution. The need to develop highly efficient and durable anode material is a never-ending challenge. Chloride, as a ubiquitous component in wastewater, can be oxidized readily to reactive chlorine species (RCS = OCl­-, HOCl, Cl·, and Cl2·-) to remove pollutants such as organics, ammonium and bacteria. However the speciation of RCS in saline water electrolysis is lacking of quantitative description. The contribution of each RCS species to pollutant removal is still under debate.
The first approach of this study is to develop multi-layer heterojunction anode for RCS generation. IrO2 is an excellent catalyst for water splitting. By depositing a thin film of TiO2 on IrO2 (Ti/Ir), the oxygen evolution reaction is hindered while the selectivity toward chlorine production is greatly enhanced. The further deposition of Sb-SnO2 islands on TiO2layer (Sn/Ti/Ir) provides additional active sites for radical generation.
As our second approach, a computational kinetic model covering chlorine generation and radical production is established. Combing it with experimental data, chlorine evolution and the furuther oxidation of chlorine to ClO3- and ClO4
- on Ti/Ir anode can be simulated. It is found that Cl·and HO· is produced concomitantly with chlorine on Sn/Ti/Ir anode and Cl2·-is the dominant radical after reaching equilibrium. The rate constant of Cl· production is two to three orders of magnitude lower than that of chlorine generation. The model predicts that the increase of chloride concentration will enhance the chlorine production but quench more radicals, which is in consistance with experimental results.
The best performing Sn/Ti/Ir anode was applied to human wastewater electrolysis. Although Cl2·- is more oxidative than chlorine, chlorine is the major contributor to the removal of organics and ammonium due to its higher concentration.

Figure 1
Interactions of Metal Oxo Species with Platinum-Based Catalysts Toward More Efficient Electrooxidation of Dimethyl Ether: Comparison to Methanol
Authors: Kulesza Pawel J , Rutkowska Iwona Agnieszka , Sek Jakub P. , Zelenay Piotr 
Published: February 2020

Methanol is so far the most commonly considered fuel as an alternative to hydrogen. However, the practical performance is limited by several factors, which include the slow kinetics of methanol oxidation and crossover of methanol from the anode to the cathode side of the cell. More recently, there has been growing interest in dimethyl ether (CH3OCH3), a gas commonly used in aerosol propellants, solvents and coolants, as a possible alternative fuel for low temperature fuel cells. Dimethyl ether (DME) is non-toxic, non-teratogenic, non-mutagenic and non-carcinogenic gas. When oxidized to CO2, a CH3OCH3 molecule releases 12 electrons. The fuel has several advantages over typical organic fuels. Unlike ethanol (CH3CH2OH), the CH3OCH3 ether does not require breaking of the C-C bond. A fairly low CH3OCH3 dipole moment results in the lower ether crossover (through the membrane) in comparison to methanol. Dimethyl ether is much less toxic than methanol and can be readily stored and transported using existing technologies. In addition, the CH3OCH3 ether has potentially higher energy density relative to methanol (namely, 8.2 vs. 6.1 kWh kg-1).
Platinum is one of the typical catalysts for the oxidation of organic molecules. It is quite active toward the dehydrogenation step, but suffers from the CO oxidation step. The bimetalic catalysts (e.g. PtRu, PtSn) can lower the onset potential of DME oxidation peak from 0.5 V for Pt/C to 0.4 V vs. Normal Hydrogen Electrode (NHE), but the maximum current densities are obtained on Pt/C.
We propose here to study the electrooxidation of DME at Pt and PtRu nanoparticles that have been deposited onto nanostructured zirconium(IV) oxide matrix (thin film on electrode surface). Zirconia is known to act as a catalytic component capable of enhancing the reactivity of the electrocatalytic system by increasing the overall acidity at the reaction interface. When combined (as a support) with Pt or PtRu centers, the existence of large population of hydroxyl groups on ZrO2 surface is believed to facilitate desorption of CO adsorbates from Pt and to induce their oxidation to CO2. In the presence of nanostructured zirconia (existing in the vicinity of the catalytic metal), the transport of protons at the electrocatalytic interface is also favored. Synergistic interactions between ruthenium and zirconia components are also feasible. In the present report, we will not limit our results to DME, but similar effects have been observed during oxidation of methanol. We are also going to consider combination of Pt or PtRu with the other metal (Pd) or metal (W, Mo) oxo nanostructures.
The support from National Research Center (NCN), Poland under the MAESTRO Project No 2012/04/A/ST4/00287 is highly appreciated.
Rhodium-Containing Multi-Layered Mixed-Metal Oxides As Active Supports for Dispersed PtRu Nanoparticles during Electrooxidation of Ethanol
Authors: Rutkowska Iwona Agnieszka , Wadas Anna , Rogalinska Aleksandra , Kulesza Pawel J 
Published: February 2020

Recently, there has been growing interest in development of fuel cells (e.g. utilizing small organic molecules) as alternative technologies to hydrogen based electrochemical energy systems. For example, ethanol (biofuel) can be ideally oxidized to carbon dioxide thus delivering twelve electrons. But realistically the reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.
Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium. Also gold in combination with platinum has been demonstrated to produce novel high performance bimetallic catalysts.
We pursue a concept of utilization of mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of methanol and ethanol. Among important issues is incorporation of Rh nanostructures capable of weakening, or even breaking, the C-C bond in the ethanol molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol is partitioned (at Rh) to methanolic residues further oxidized at PtRu cannot be excluded.
Electrochemical Reduction CO2 to Formate on Cuxo Electrode
Authors: Qiao Jinli 
Published: February 2020

In recent years, CO2 conversion using electrochemical catalysis approaches has attracted great attention due to its several advantages such as the controllable electrode potentials, reaction temperature and the recycled supporting electrolytes1. But the low performance of the electrocatalysts (i.e., low catalytic activity and insufficient stability) hinders its practical application1.
Cu have been explored to catalyze CO2 electroreduction due to its low cost, abundant reserve and reasonable overall Faradaic efficiency towards fuel production(e.g. CO, CH4, C2H4, formate, alcohols)2. However, the energetic efficiency of Cu is limited by the large overpotential (>0.7 V) required for CO2 reduction to outcompete H2O reduction3. Furthermore, Cu electrode rapidly lose their CO2 reduction activity2. Achieving efficient Cu-catalyzed CO2 reduction requires preparing Cu particles whose surfaces have active sites that are different from those on the surface of a metallic Cu electrode4. Here, we prepared CuxO particles by a simple one-step hydrothermal synthesis, and applied them to the gas diffusion electrode, these electrodes exhibited good electrochemical performance of high catalytic activity and high selectivity.
The CuxO were prepared using a simple hydrothermal method as follows: 0.04 mol Cupric Acetate Monohydrate and 0.02mol hexamethylenetetramine were mixed under stirring to form a homogeneous solution. Then the mixture was transferred into a 100 mL stainless-steel autoclave and heated at 180℃ for 2 h. Then the precipitate was collected by centrifugation, washed with deionized water and absolute ethanol for several times, until the pH was neutral, finally dried at oven at 85℃ for 12h.
The crystal structure of the product was characterized by XRD and SEM. The catalyst electrode was prepared by CuXO powder bonded with Nafion solution and isopropanol, and spread over the gas diffusion layer (GDL). The catalytic activity of CuXO nanocatlyst supported on GDL as the cathode electrode was measured using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in 0.5M KHCO3 aqueous solution saturated with both N2 and CO2, respectively.
Figure 1 shows the CV curves on the CuxO/GDL electrode. It can be seen that the anodic peaks between 0V~ 0.85V and the cathodic peak between -0.6V~ 0.25V. The onset potential in 0.5M KHCO3 solution saturated with CO2 was found to be at 0.20 V, which is 250 mV more positive than that under N2 ( 0 V). At an potential of -1.25V, the current density in CO2-saturated 0.5M KHCO3
reached 17.1 mAcm-2 (Fig. 1). All the above reults indicates that participation of CO2 reduction contributes to the enhancement of cathodic current.
References
1. J. L. Qiao, Y. Y. Liu, Y. Y, F. Hong, J. J. Zhang. Chem. Soc. Rev., 43, 631 (2014 ).
2. Y. Hori, H. Konishi, T. Futamura, A. Murata, O. Koga, H. Sakurai, K.Oguma. Electrochimica Acta 50 (2005) 5354–5369.
3. Y.Hori, A.Murata, R.Takahashi. J.Chem. Soc., Faraday Trans. 1, 1989, 85, 2309-2326
4. W. Li Christina and W. Kanan Matthew. J. Am. Chem. Soc. 2012, 134, 7231−7234

Figure 1
Analysis of High Temperature Co-Electrolysis Cells Via Electrochemical and Surface Spectroscopy
Authors: Call Ann V , Tumilson Christopher , Cumming Denis J , Taylor S.F. Rebecca , Hardacre Chris , Elder Rachael H 
Published: February 2020

CO2 emissions are a significant environmental problem which has garnered global interest from both the scientific and political community. One method to reduce emissions is to capture CO2 and convert it to useful products, such as chemical feed-stocks. A method to achieve this is via co-electrolysis of CO2 and H2O, using a high temperature solid oxide cell, to produce synthesis gas – an important intermediate to the production of synthetic liquid fuels.
The potential to convert CO2 into synthetic fuel forms a major pathway for global CO2 utilization and could address the issues of depleting fossil fuel reserves and global warming, however, the reaction mechanisms occurring during cell operation for a co-electrolysis system are currently not well understood. This information is necessary to improve performance by engineering materials and operating conditions which are ideal for high gas conversion rates and long term cell performance. Previous studies have suggested that carbonate species may be an important intermediate to CO2 reduction during electrolysis and shows dependencies with temperature and applied potential.[1] This study investigates the electrochemical impedance of electrolysis cells to determine potential rate limiting mechanisms occurring during cell operation. Results correlating cell performance to surface species detected in-situ using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) obtained under varying fuel and temperature conditions will be discussed.

[1] D.J. Cumming, C. Tumilson, R. Taylor, S. Chansai, A.V. Call, J. Jacquemin, C. Hardacre, R.H. Elder,
Faraday Discuss., 2015, 182, 97-111
(Science for Solving Society’s Problems Challenge Grant Winner) SPEED: Sanitation and Processing for Energy with Electrochemical Devices
Authors: Reguera Gemma 
Published: February 2020

In Nature, highly efficient and diverse consortia of microbes process organic matter, such as agricultural and human wastes, while generating energy for growth and recycling carbon and other vital elements. Driving these reactions are organisms with the ability to extract electrons from the chemical substrates and transfer them to redox-active minerals. One group in particular, Geobacter bacteria, can couple their metabolism to the reduction of insoluble minerals such as iron and manganese oxides. This natural process can be mimicked in electrochemical devices, which provide a poised electrode as electron sink to drive the growth and catalysis of the bacteria. The SPEED technology capitalizes on the synergistic interactions between Geobacter bioelectrodes and targeted bioprocessing microbes to simultaneously sanitize and harvest energy from wastes. The partnership between the two microbes in such Nature-inspired reactors promotes the processing of agricultural, industrial, and human wastes while generating added-value products and enabling water reuse. The versatility of the SPEED technologies is illustrated with scaled-up reactor prototypes which simultaneously process human urine while harvesting energy from waste substrates as biofuels and industrial chemical precursors. Furthermore, SPEED processes can be adapted to any reactor vessels and use inexpensive electrode materials to promote the microbial catalysis. They are deployable and scalable and can be customized to adapt to the needs of the target market, from decentralized systems for sanitation and water reuse to industrial reactors for bioenergy applications.