Electrochemical Desorption Research Articles

Anode process on gold in KF–AlF<sub>3</sub>–Al<sub>2</sub>O<sub>3</sub> melt

In the conditions of resource saving and carbon footprint reduction, the development of oxygen–releasing anodes for technologies of production of important metals and alloys by electrolysis of molten salts seems to be an urgent task. To determine the degree of “inertness” of a particular anode material, data on the kinetics and mechanism of the anode process on a material not subject to oxidation are required. In this connection, the anodic process on gold in the KF–AlF3–Al2O3 melt for electrolytic aluminum production was investigated by cyclic and square–wave voltammetry methods. The influence of temperature (715 and 775 оC) of the melt, the content of Al2O3 in it (from 0.1 to saturation), as well as the polarization rate (0.05–1 V/s) on the kinetics and some features of the mechanism of the investigated process was determined. An assumption is made that oxygen release on gold without dissolution of the substrate takes place in the region of overvoltages from 0 to 0.8 V. It is shown that the process includes the stages of electrochemical adsorption and desorption of the intermediate product, the first of which is limited by the diffusion of electroactive anions to the anode.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2% decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

Enhancement of direct electron transfer by aromatic thiol modification with truncated d-fructose dehydrogenase

A heterotrimeric membrane-bound d-fructose dehydrogenase (FDH) from Gluconobacter japonicus, composed of subunits L, C, and S, shows strong direct electron transfer (DET)-type bioelectrocatalytic performance in the two-electron oxidation of d-fructose. The electrode-active site of the enzyme is the heme c moiety in the subunit C. A previous study reported the construction of the subunit L/S subcomplex (ΔC FDH) lacking the subunit C. In this work, we attempted to realize the DET-type reaction of ΔC FDH using porous gold electrodes functionalized with several thiols, and investigated the influence of the thiols on DET. Kinetic analysis of the steady-state catalytic waves revealed that the electrode-active site of ΔC FDH is the [3Fe-4S] iron-sulfur cluster in the L subunit. The experimental results demonstrated that uncharged aromatic thiols on the electrode enhance the DET-type reaction of ΔC FDH. Based on the pH-dependent profile of the DET-type activity and the surface conditions of the modified thiols evaluated by electrochemical reductive desorption, we suggest an enhancement mechanism for DET by aromatic thiols.

A new look at metal–carbon hybrids: Molecular-scale study of covalently grafted gold

The reliable integration of new nanocarbons in future molecular and hybrid electronics requires mastery of chemical binding between dissimilar materials down to the individual bond. Here, we present a detailed study of covalent grafting of aryl radicals on single crystal Au(111), and investigate their electrochemical stability and oxidative desorption. Copper underpotential deposition and Gaussian deconvolution of its current–potential trace are used to map the thermodynamic and kinetic landscape of the modified Au surface. Scanning tunnelling microscopy in a high-boiling organic solvent suggests that grafting is accompanied by vacancy island formation on the Au surface, while iodide adsorption heals these vacancies and allows high-contrast imaging of individual covalent grafts.

Low-energy electrochemical CO2-amine desorption driven by the proton-coupled electron transfer reaction (PCET)

The CO2 desorption in amine-based carbon capture processing is accompanied by significant energy consumption, accounting nearly 70% of energy requirements of the entire process. Electrochemical CO2 capture and release are promising technologies to reduce the energy consumption. The characteristics and CO2 desorption performance of QH2 (Tiron) in tertiary amine systems are investigated in this research. The reducing ability of Q (Oxidized QH2) was improved by modifying the electrode to achieve low-energy electrochemical desorption. The CO2 electrochemical desorption achieved low-energy CO2 desorption of 0.7 GJ ton−1 CO2 against over 2.4 GJ ton−1 in a conventional and mature MEA-based system.

Effect of Ce replacing La on the electrochemical performance of amorphous grain boundaries Mg-Ni-based materials

Aiming at enhancing the electrochemical characteristic of RE-Mg-based composite, the partial substituting La with Ce experiment in the composites was conducted, and the surface modification treatment of the alloys was performed by mechanical coating Ni. By means of mechanical trituration, The La10-xCexMg80Ni5 (x = 0–2) + y wt% Ni (y = 50–200) compound materials which have the structures of nanocrystalline and amorphous were synthesized. In order to make sense of the principle action of Ce and Ni elements in structural and electrochemical properties of the material, some deep research were carried out. According to the final results, the as-milled composites have the electrochemical hydrogen absorption and hydrogen desorption abilities at room temperature. Having no use for activation, the as-milled composites can reach the maximum discharge capacities when the first cycling was carried out. With the Ni value x changed from 50 to 200, the discharge capacity was varied from 70.5 mAh/g to 902.1 mAh/g; moreover, the capacity retention rate at 20th cycle (S20) and high rate dischargeability (HRD) of the (x = 0) composite were heightened from 67.2 % to 82.3 %, from 50.6 % to 55.7 % respectively. The composites' (y = 100) discharge capacity has a maximum value 118.5 mAh/g when the Ce value x is 1. The capacity retention rate (S20) is enhanced from 53.3 % to 68.5 % by lifting Ce content from x = 0 to x = 2. what's more, the high-rate discharge ability (HRD), the electrochemical impedance spectrum (EIS), potentiodynamic polarization curves, and potential-step measurements all intimate that substituting La with Ce clearly promotes the composites' electrochemical kinetic properties, but maximum values emerge only when the x value is 1.

Biogenically synthesized palladium nanoparticles for hydrogen evolution study: An efficient catalyst for 4-nitrophenol reduction and C-C coupling reactions

Indian cork extract is employed for the greener production of palladium nanoparticles (Pd NPs) an effective heterogeneous catalyst with a concentration of 30.1%. Plant extract-mediated phytochemicals were found responsible for reducing Pd(II) to Pd(0) without the aid of an external reducing agent. XRD, UV–visible, and other analyses demonstrated the successful formation of Pd NPs. These NPs were evident to have better electrocatalytic activity in the hydrogen evolution reaction (HER) in an acidic medium. The Tafel slope (174 mV/dec) of the Pd NPs catalyst confirmed the Volmer-Heyrovsky mechanism for HER study and demonstrated the electrochemical desorption of hydrogen is the rate-determining step. In terms of synthetic organic chemistry perspectives, the applicability of Pd NPs has been subsequently demonstrated for the reduction of toxic 4-nitrophenol to synthetically important 4-aminophenol with a minimum catalyst loading at ambient conditions. Additionally, the outstanding catalytic activity of synthesized heterogeneous Pd NPs catalyst has been showcased for direct Heck and Hiyama cross-coupling reactions.

Nanostructured Black Silicon as a Stable and Surface-Sensitive Platform for Time-Resolved In Situ Electrochemical Infrared Absorption Spectroscopy.

Attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is a powerful method for probing interfacial chemical processes. However, SEIRAS-active nanostructured metallic thin films for the in situ analysis of electrochemical phenomena are often unstable under biased aqueous conditions. In this work, we present a surface-enhancing structure based on etched black Si internal reflection elements with Au-coatings for in situ electrochemical ATR-SEIRAS. Using electrochemical potential-dependent adsorption and desorption of 4-methoxypyridine on Au, we demonstrate that black Si-based substrates offer advantages over commonly used structures, such as electroless-deposited Au on Si and electrodeposited Au on ITO-coated Si, due to the combination of high stability, sensitivity, and conductivity. These characteristics are especially valuable for time-resolved measurements where stable substrates are required over extended times. Furthermore, the low sheet resistance of Au layers on black Si reduces the RC time constant of the electrochemical cell, enabling a significantly higher time resolution compared to that of traditional substrates. Thus, we employ black Si-based substrates in conjunction with rapid- and step-scan Fourier transform infrared (FTIR) spectroscopy to investigate the adsorption and desorption kinetics of 4-methoxypyridine during in situ electrochemical potential steps. Adsorption is shown to be diffusion-limited, which allows for the determination of the mean molecular area in a fully established monolayer. Moreover, no significant changes in the peak ratios of vibrational modes with different orientations relative to the molecular axis are observed, suggesting a single adsorption mode and no alteration of the average molecular orientation during the adsorption process. Overall, this study highlights the enhanced performance of black Si-based substrates for both steady-state and time-resolved in situ electrochemical ATR-SEIRAS, providing a powerful platform for kinetic and mechanistic investigations of electrochemical interfaces.

Highly selective capture of cesium using an electrochemically renewable molybdenum-based crystalline adsorbent

The development of highly efficient adsorbents for the capture of 133Cs and the removal of radioactive isotope 137Cs from complex aqueous solutions is crucial for the chemical production and environmental remediation. Herein, Mo-based crystalline adsorbent with sub-nanometer (5.76 Å) channels was successfully prepared and used in electrochemically controlled Cs+ separation process. Crystalline structures of MoIC (HNO3) before and after adsorption of Cs+ were clearly elucidated using powder X-ray diffractometer (PXRD). A more environmentally friendly electrochemical method was employed to achieve easy release and recapture of Cs+. Adsorption comparison experiments revealed that our material clearly outperforms the reported adsorbents for the removal or recovery of trace amount of Cs+ (< 10 mg L−1). Furthermore, MoIC (HNO3) also exhibited excellent selectivity for low concentration of Cs+ over highly excess of competitive cations, such as Mg2+, Ca2+ and K+, which are commonly distributed in brines. The maximum separation factors of Cs+/Mg2+, Cs+/Ca2+ and Cs+/K+ are 1.2 × 105, 1.3 × 104 and 66, respectively. The remarkable selectivity can be attributed to the outstanding ion-sieving ability of sub-nanometer channels based on the differences in ionic radius and hydration energy of these cations. A real brine was introduced to further prove that one complete cycle of electrochemical adsorption and desorption can dramatically reduce the competing ions concentrations up to 980 times. We anticipate that our findings may give the prospect of opening up new path for the efficient separation of Cs+ from brines using molybdenum-based adsorbent via electrochemically controlled process as a green and sustainable way.

EFFECT OF SURFACE TREATMENT ON THE ELECTROCHEMICAL ACTIVITY OF Ti3SiC2/TiC/TiSi COMPOSITE MATERIAL IN THE HYDROGEN EVOLUTION REACTION

The effect of treatment of the surface layer of the Ti3SiC2/TiC/TiSi composite material on its electrochemical activity in the of hydrogen evolution reaction in 0.5M H2SO4 has been studied. Surface treatment has been carried out by chemical etching in solutions of 15, 30, 45% HF for 15, 30, 45 min at 25 and 60 °C. It has been established that the cathodic polarization curves of the Ti3SiC2/TiC/TiSi-electrode without and with surface treatment have a Tafel section with a slope of 0.060–0.076 V and they are characterized by an overvoltage value of 0.20–0.26 V at i = 1 mA/cm2. The rate of the cathodic reaction as a result of treatment increases by ~1.6-9.8 times. The greatest increase is caused by high-temperature etching in a solution of 30% HF for 30 min while stirring the solution. The impedance spectra of the Ti3SiC2/TiC/TiSi-electrode at Tafel region potentials consist of a capacitive semicircle with a displaced center. On the impedance graphs of the treated electrode, a straight section with a slope above 45º was registered in the region of the highest frequencies, indicating the presence of pores in the surface layer of the electrode. To describe the hydrogen evolution reaction on Ti3SiC2/TiC/TiSi, we used an equivalent electrical circuit, the Faraday impedance of which consists of charge transfer resistances R1 connected in series and a parallel R2C2-chain corresponding to the adsorption of atomic hydrogen on the electrode surface. The equivalent circuit also includes the electrolyte resistance Rs and the double layer capacitance impedance, which is modeled by the constant phase element CPE1. It has been shown that the results of polarization and impedance measurements agree satisfactorily with the discharge–electrochemical desorption mechanism with a quasi-equilibrium discharge stage when the logarithmic Temkin adsorption isotherm for adsorbed atomic hydrogen is fulfilled. It has been concluded that the composite material Ti3SiC2/TiC/TiSi in sulfuric acid electrolyte is a promising electrode material for the electrochemical production of hydrogen.

Battery Electrode-Based Lithium Recovery from Geothermal Brines

Driven by the electrification of transport sector the demand of lithium for battery application is increasing exponentially. The major sources for lithium are continental brines and hard minerals where the production comes along with consumptive water requirements and energy intensive processing and extraction. Therefore, it is of tremendous importance to consider alternative, non-conventional, sources and to develop more efficient and environmentally benign Li extraction methods. Geothermal brines can have significant Li concentrations (150–240 mgLi+ L−1)[1] and could represent an attractive sustainable lithium source. Implementing electrochemical methods for lithium extraction offers further advantages of high Li-selectivity, minimal waste production and low water consumption.[2] Here, we present a dual-ion battery type setup for the selective electrochemical Li-adsorption and desorption from geothermal brines. The chloride concentration in brines is a thousand times higher than that of Li+, hence, both species can be captured at opposite electrode sides. In the dual-ion setup presented in this work, Li+ are stored in a Li-selective LiFePO4(LFP) battery electrode and Cl− are stored using bismuth oxychloride (BiOCl) as counter electrode that has shown excellent Cl− storage capabilities and chemical stability in chloride-ion batteries and desalination batteries.[3] In the second step, both ions are released in a recovery solution to yield a Li-rich solution that could be further processed into battery-grade lithium hydroxide or carbonate. The stability of LFP in aqueous solutions and high Li -selectivity makes it a favored candidate for the electrochemical recovery of Li from natural solutions, where a diverse mixture of cations and anion is present.[4] Therefore, we examined the stability of the electrodes in brine solutions by XRD, indicating good reversibility and no intercalation of competitor ions. In addition, the Li-selectivity in extraction/recovery experiments was analyzed by ICP-OES and influences of different process parameters (e.g. current density, pH, temperature) were investigated. The results demonstrate that the LFP/BiOCl dual-ion battery setup is a feasible and promising low cost method for environmentally friendly Li extraction from geothermal brines.

Catch and release: Gold adsorption and sorbent electrochemical regeneration

Wastewater generated from e-waste leaching is rich in precious metals including gold, silver and platinum. Conventional precipitation and solvent extraction are chemically intensive separations with concerning environmental externalities. Sorbents, in particular carbon nanotubes, have low chemical consumption, and have shown promise for gold adsorption due to their high specific surface area and chemical functionalization potential. However, regenerating sorbents used to adsorb Au is hazardous requiring strong acids. Herein, we delineate the effect of various functional groups on the sidewalls of multiwall carbon nanotubes (MWCNTs) on gold adsorption, and we introduced an acid-free electrochemical technique for Au elution from MWCNTs. Pristine MWCNTs (P-MWCNTs), carboxylic functionalised MWCNTs (COOH-MWCNTs) and amide functionalised MWCNTs (NH2-MWCNTs) were compared for their affinity for Au adsorption from acidic AuCl4−solutions mimicking acidic e-waste leachate. Au adsorption affinity onto MWCNTs followed the order of P-MWCNT > NH2-MWCNT > COOH-MWCNTs. Au elution from Au-saturated MWCNTs was subsequently achieved up to 65%, using acid-free electrochemical desorption in neutral aqueous brine. The Au electro-desorption was shown to have a direct relationship with both the applied current and the mass of the Au adsorbed on the MWCNTs. This study demonstrates enhanced adsorption-based preconcentration of gold and acid-free regeneration of sorbents.

Investigation on the performance of EDA-based blended solvents for electrochemically mediated CO2 capture

EDA-Cu based electrochemically mediated CO2 capture method was developed as a promising technology to substitute the conventional amine-based CO2 capture, especially in industries without available steam source. However, the highly corrosive and poor Cu cycling performance seriously obstruct its large-scale application. In this work, traditional primary amine, secondary amine and tertiary amine (MEA, DEA and TEA) are chosen to blend with EDA to alleviate the problems of EDA. Electrochemical measurements, corrosiveness comparison, CO2 absorption and desorption performance were conducted to investigate the advance performance of proposed blended solvents comprehensively. The corrosion potential in all the mixtures is significantly higher than that in sole EDA solution, which illustrates that the corrosiveness of proposed mixed solvents to Cu electrode is weaker. Besides, the Cu cycling performance is greatly improved and the energy consumption is significantly reduced by using blended solvents. Overall, 50/50 EDA/MEA mixed solution with high CO2 capacity and fast absorption rate is suggested to be a substitute for traditional EDA solvent. The CO2 desorption energy consumption of 50/50 EDA/MEA mixed solution decreases 14% than that of EDA solution at a current density of 0.01 A/cm2. Meanwhile, the copper cycling performance is also improved in 50/50 EDA/MEA mixed solution as the cathode Faraday efficiency (CFE) increased from 43% (EDA) to 53% (50/50 EDA/MEA). Results show that the proposed mixed amine solvents lead to the successful circumvention of highly corrosive and poor Cu cycling performance in the electrochemically mediated CO2 capture system, which will contribute to the exploration of efficient blended solvents for EMAR CO2 capture process and promote its industrial application.

TECHNOLOGICAL INDICATORS OF THE CATHODIC PROCESS IN THE REGENERATION OF USED SULFO-ACID SOLUTIONS FOR ETCHING STEEL

The current state of regeneration of sulfate solutions was analyzed, it was established that the existing physico-chemical methods do not solve the problem of regeneration of sulfuric acid, but only neutralize it, for transfer according to the standards of the MPC to neutralization and into the sewage system with subsequent disposal. It has been confirmed that it is advisable to carry out the regeneration by an electrochemical method using a three-chamber electrolyzer, when the solution is fed into the middle chamber, the concentration of regenerated sulfuric acid increases to 180-200 g/l, with simultaneous iron deposition, with a current yield of 65-70%. This method reduces waste and allows switching to a closed cycle on sulfuric acid. It was found that in the process of digestion, the concentration of sulfuric acid decreases from 2.0 to 0.5 mol·dm-3, and the concentration of iron (II) sulfate increases accordingly. Under the conditions of a decrease in the concentration of sulfuric acid, its chemical activity also decreases when interacting with iron oxides and hydroxides. To increase the reactivity of pickling solutions, an increase in the temperature of the entire process is used. The kinetic regularity of combined cathodic processes in model solutions of iron (II) sulfate with sulfuric acid was established. Platinum, copper and carbon steel were used as cathode material. The choice of the cathode material was based on the different electrochemical properties of these selected metals with respect to the hydrogen reaction. The main process at the platinum cathode is hydrogen release in a wide range of current densities. At current densities greater than 0.1 A/cm2, a sharp increase in potential was observed due to the incorporation of Fe2+ into the composition of the cathode-electrolyte interface, but Fe2+ reduction potentials were not reached. When replacing the cathode material from platinum to carbon steel, a significant inhibition of hydrogen release was observed, which made it possible to reach the potentials for the simultaneous reduction of hydrogen and iron, however, the maximum current of the rectilinear section of the electrochemical process with electrochemical control was reduced from 10 at 20 0C to 3 times at 80 0C. The use of a copper cathode made it possible to reveal the influence of the hydrogen reaction on the course of Fe2+ reduction. The release of hydrogen at the copper cathode was accompanied by a significant inhibition of the hydrogen ion discharge. When using an iron cathode, electrochemical desorption is the limiting stage, which leads to the existence of layers of adsorbed hydrogen firmly attached to the surface of the iron cathode. A comparative analysis of the voltage-current dependences for the final investigated temperatures indicates a significant effect of an increase in temperature from 20 0C to 80 0C by approximately 120-150 mV. The cathodic process at 20 0C takes place in the mode of increased kinetics for both combined processes. At 80 0С, rectilinear sections of electrochemical control of the cathodic process appear on the voltage–voltage dependences, at Fe2+ concentrations of 1.0 and 1.5 mol/dm3. These areas range from 20 to 60 mA/cm2. The concentration of iron ions and the temperature of electrolysis have a significant effect on the process of electrochemical reduction of Fe2+, which was confirmed experimentally. Since the target process in the electrochemical regeneration of spent pickling solutions is the regeneration of sulfuric acid itself, and not the removal of Fe2+ from this solution, the cathodic mode of operation of the electrode unit was determined according to the technological indicators of the anodic process.

First-principles analysis of electrochemical hydrogen storage behavior for hydrogenated amorphous silicon thin film in high-capacity proton battery

Silicon material electrodes as proton carriers for high-capacity proton battery have only been proposed for such a short period of time that their physicochemical properties and electrochemical hydrogen storage behavior during charge and discharge processes remain nearly uncharted territory. Herein, the hydrogenated amorphous silicon (a-Si:H) thin film electrodes are prepared by radio frequency sputtering followed by ex-situ hydrogenation. The electrochemical properties of a-Si:H electrodes are tested experimentally, and the electrochemical hydrogen storage behaviors of a-Si:H electrodes are analyzed by first-principles calculations. The results show that the hydrogenation process significantly increases the electrochemical capacity of the electrodes and reduces the band gap of the electrode structure. The electrode exhibits weak conductivity during the initial charging, but the instability of the electrode electronic structure during the later charging results in a slight fluctuation of the electrochemical charging process. The a-Si:H electrode have better electrochemical hydrogen storage/release reversibility than non-hydrogenated electrodes, but this reversibility is weakened by oxygen atoms covered on the electrode surface. The electrochemical hydrogen storage process is easier to accomplish than the electrochemical desorption process of hydrogen evolution reaction for the a-Si:H electrodes. The a-Si:H thin film electrode is more stable on the Ni(111) substrate surface and the good conductivity of the electrode/substrate interface provides convenient conditions for the free transport of electrons in the electrochemical charge/discharge processes. We believe that these results perfectly explain the microscopic mechanisms responsible for the electrode reaction and electrochemical behavior of a-Si:H electrodes in this type of proton battery, and have a certain reference value in understanding the physicochemical properties and electrochemical hydrogen storage behavior of silicon material electrodes applied to other types of batteries during charge/discharge processes.

Unveiling the Multistep Electrochemical Desorption Mechanism of Cubic NiO Films for Transmissive-to-Black Electrochromic Energy Storage Devices.

Electrochromic smart windows offer dynamic control of sunshine and solar heat in modern architecture. Yet, how to obtain aesthetically pleasing color tuning states such as gray and black is a great challenge, and the corresponding desorption mechanism in electrochromism is still not well understood. Here, we report one transmissive-to-black NiO electrochromic film assembled by a facile and low-cost electrostatic spray technology, which achieves ultralarge optical modulation, high coloration efficiency, and remarkable energy storage capacity. By in-depth experimental analyses and the first-principle calculations, multistep electrochemical desorption mechanisms of OH- and electrochromic switching kinetics of the NiO film were unveiled. Additionally, the assembled NiO film-based smart energy storage indicator can visually display its energy storage level in real time. Our obtained NiO films and subsequent devices can serve as potential candidates in a broad range of innovative electrochromic applications including multifunctional smart windows, energy-efficient displays, energy-storage indicators, electronic labels, etc.

Synthesis of PtAu Alloy Nanocrystals Supported on Three-Dimensional Carbon with Enhanced Electrocatalytic Properties

Sub-nanosized PtAu particles within three-dimensional carbon materials were obtained via a mercaptosilane-assisted preparation method. This strategy can effectively control the size of PtAu particles while avoiding the use of an additional carbon precursor. The as-synthesized three-dimensional carbon (3D carbon) material possesses excellent properties compared to other carbon materials. PtAu particles on three-dimensional carbon (PtAu/3D carbon) exhibited superior activities for methanol oxidation and hydrogen evolution reactions compared to Pt/3D carbon and a commercial Pt/Carbon (Pt/C) catalyst. Specifically, the methanol peak current density on PtAu/3D carbon was almost 2.3 times higher than that of Pt/3D carbon and 1.9 times higher than that of commercial Pt/C. The Tafel slopes of PtAu/3D carbon, Pt/3D carbon, and the commercial Pt/C were approximately 112, 124, and 106 mV dec−1, respectively, demonstrating that electrochemical desorption is the rate-limiting step in the hydrogen evolution reaction of the as-synthesized catalysts.

Efficient removal of Cs ion by electrochemical adsorption and desorption reaction using NiFe Prussian blue deposited carbon nanofiber electrode.

Prussian blue (PB) analog (NiFe, CoFe, FeFe, and commercial(cPB)) decorated carbon nanofiber (CNF) electrodes were synthesized by the drop casting method in this study to investigate the interaction between PB and CNF for the electrochemical adsorption (EA) and electrochemical desorption (ED) of Cs ion (Cs+). The adhesion of PB on the electrode and the EA and ED of Cs+ were substantially higher when the CNF electrode was used, compared with the fluorine-doped tin oxide supporting electrode. The use of CNF led to the smooth occurrence of EA and ED of Cs+, where the reported efficiency was: NiFe >FeFe >cPB. The EA and ED of Cs+ on NiFe decorated CNF (C-NiFe) were strongly affected by the loading amount of NiFe. Although the strongest EA capacity was identified when 1mg of NiFe was used, it decreased as the loading amount of NiFe increased. Thus, the EA of Cs+ occurs under the reduction of NiFe with some Fe(III) reduced to Fe(II) of NiFe, thus inducing more adsorption of Cs+. Overall, we confirmed that the C-NiFe electrode with appropriate thickness of NiFe layer is potentially an excellent adsorbent for Cs removal.

Selective and quantitative recovery of sulfadiazine from seawater by Sb doped LTA zeolite electrochemical sensor

The sensitive Sb probe has been anchored in the LTA (Linde Type A) zeolite to form a bifunctional sensor for the electrochemical detection and recycling of sulfadiazine (SDZ) in seawater. Under Amperometric i-t Curve (A i-t C) method, SDZ is quantitatively adsorbed on the Sb LTA zeolite electrode from seawater by adjusting the reduction time and potential. Under differential pulse voltammetry (DPV) method, a characteristic peak is observed at ca. 0.80 V whose intensity can indicate the SDZ concentration on the novel modified electrode. Also, SDZ can be selectively released to phosphate-buffered saline (PBS) in the potential range of 0.80–0.95 V. The electrochemical mechanism of the reversible recovery reaction is carefully studied by the cyclic voltammetry (CV) method and confirmed by the X-ray Photoelectron Spectroscopy (XPS) analysis results related to the interaction between the electrode material and SDZ before and after electrochemical process. Sb doped on LTA zeolite presented a cubic phase from SEM images, and there are some SDZ particles accumulated and adsorbed on the surface of the crystal from TEM images. Theoretical calculation results reveal that SDZ is stable in the electrochemical adsorption and desorption process due to the interaction between the SDZ molecules and the 8-ring opening windows of LTA zeolite framework. The transfer efficiency of SDZ could reach 9.62 μg / 100 s or 0.430 g / 1 g based on the mass of Sb probe. The multifunctional sensor suggests a novel strategy for the electrochemically controlled detection and recovery toward antibiotic sulfadiazine.

Novel coumarin substituted N–heterocyclic carbene Ag(I), Au(I) and Ni(II) complexes as electrocatalysts in hydrogen evolution reactions from water

An organized strategy with an analogy in controlling steric and electronic parameters of N-heterocyclic carbene (NHC) Ag (5–10), Au (11/12) and Ni (13/14) complexes as molecular electrocatalysts for engineering hydrogen evolution reaction (HER) from water is revealed. The films of 10, 13 and 14 displayed much improved activity with low overpotential −298 to −355 mV vs. RHE to drive a current density of 10 mA/cm2 (Tafel slope = 70–78 mV/dec) with exchange current density of 18–49 μA/cm2. Latter observation authenticates that the HER proceeds by the electrochemical desorption of molecular hydrogen through Volmer–Heyrovsky step. Further, the durability test suggests much lower decay rate of 11.4 and 23.1% for complexes 10 and 14 after 200 cycles, respectively. Finally, Cdl and Rct were calculated using electrochemical impedance spectroscopy. The superior activity of former complexes was manifested by the NHC design and their microcrystalline porous morphology.