Electrochemically Grown Ultrathin Platinum Nanosheet Electrodes with Ultralow Loadings for Energy-Saving and Industrial-Level Hydrogen Evolution

Nanostructured catalyst-integrated electrodes with remarkably reduced catalyst loadings,high catalyst utilization and facile fabrication are urgently needed to enable cost-effective,green hydrogen production via proton exchange membrane electrolyzer cells(PEMECs).Herein,benefitting from a thin seeding layer,bottom-up grown ultrathin Pt nanosheets(Pt-NSs)were first deposited on thin Ti substrates for PEMECs via a fast,template-and surfactant-free electrochemical growth process at room temperature,showing highly uniform Pt surface coverage with ultralow loadings and vertically well-aligned nanosheet morphologies.Combined with an anode-only Nafion 117 catalyst-coated membrane(CCM),the Pt-NS electrode with an ultralow loading of 0.015 mgPt cm−2 demonstrates superior cell performance to the commercial CCM(3.0 mgPt cm^(−2)),achieving 99.5%catalyst savings and more than 237-fold higher catalyst utilization.The remarkable performance with high catalyst utilization is mainly due to the vertically well-aligned ultrathin nanosheets with good surface coverage exposing abundant active sites for the electrochemical reaction.Overall,this study not only paves a new way for optimizing the catalyst uniformity and surface coverage with ultralow loadings but also provides new insights into nanostructured electrode design and facile fabrication for highly efficient and low-cost PEMECs and other energy storage/conversion devices.

Electrochemically triggered decoupled transport behaviors in intercalated graphite:From energy storage to enhanced electromagnetic applications

Pyrolytic graphite (PG) with highly aligned graphene layers,present anisotropic electrical and thermal transport behavior,which is attractive in electronic,electrocatalyst and energy storage.Such pristine PG could meeting the limit of electrical conductivity (~2.5×10^(4) S·cm^(−1)),although efforts have been made for achieving high-purity sp^(2) hybridized carbon.For manipulating the electrical conductivity of PG,a facile and efficient electrochemical strategy is demonstrated to enhance electrical transport ability via reversible intercalation/de-intercalation of AlCl_(4)^(-)into the graphitic interlayers.With the stage evolution at different voltages,variable electrical and thermal transport behaviors could be achieved via controlling AlCl_(4)^(-)concentrations in the PG because of substantial variation in the electronic density of states.Such evolution leads to decoupled electrical and thermal transport (opposite variation trend) in the in-plane and out-of-plane directions,and the in-plane electrical conductivity of the pristine PG (1.25×10^(4) S·cm^(−1)) could be massively promoted to 4.09×10^(4) S·cm(AlCl_(4)^(-)intercalated PG),much better than the pristine bulk graphitic papers used for the electrical transport and electromagnetic shielding.The fundamental mechanism of decoupled transport feature and electrochemical strategy here could be extended into other anisotropic conductive bulks for achieving unusual behaviors.

Electrochemically reduced graphene oxide with enhanced electrocatalytic activity toward tetracycline detection

An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） detection compared to the ERGO-12v （GO applied to a negative potential of-1.2 V）, GO, chemically reduced GO （CRGO）-modified glassy carbon electrode （GC） and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8v-modifled glass carbon electrode （GC/ERGO-0.8v） were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L Physical characterizations with Fourier transform infrared （FT-IR）, Raman, and X-ray photoelectron spectroscopies （XPS） demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8v electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.

Electrochemically exfoliated graphene as high-performance catalyst support to promote electrocatalytic oxidation of methanol on Pt catalysts

Electrochemically exfoliated graphene(EEG)is a kind of high-quality graphene with few oxygen-containing functional groups and defects on the surface,and thereby is more suitable as catalyst support than other carbon materials such as extensively used reduced graphene oxide(rGO).However,it is difficult to grow functional materials on EEG due to its inert surface.In this work,ultra-small Pt nanocrystals(~2.6 nm)are successfully formed on EEG and show better electrocatalytic activity towards methanol oxidation than Pt catalysts on r GO.The outstanding catalytic properties of Pt catalysts on EEG can be attributed to the fast electron transfer through EEG and high quality of Pt catalysts such as small grain size,high dispersibility and low oxidation ratio.In addition,SnO2 nanocrystals are controllably generated around Pt catalysts on EEG to raise the poison tolerance of Pt catalysts through using glycine as a linker.Owing to its outstanding properties such as high electrical conductivity and mechanical strength,EEG is expected to be widely used as a novel support for catalysts.

High-performance zinc-ion batteries enabled by electrochemically induced transformation of vanadium oxide cathodes

Rechargeable aqueous zinc-ion batteries(ZIBs) have become a research hotspot in recent years,due to their huge potential for high-energy,fast-rate,safe and low-cost energy storage.To realize good electrochemical properties of ZIBs,cathode materials with prominent Zn^(2+) storage capability are highly needed.Herein,we report a promising ZIB cathode material based on electrochemically induced transformation of vanadium oxides.Specifically,K_(2) V_6 O_(16)·1.5 H_(2) O nanofibers were synthesized through a simple stirring method at near room temperature and then used as cathode materials for ZIBs in different electrolytes.The cathode presented superior Zn^(2+) storage capability in Zn(OTf)_(2) aqueous electrolyte,including high capacity of 321 mAh/g,fast charge/discharge ability(96 mAh/g delivered in 35 s), high energy density of 235 Wh/kg and good cycling performance.Mechanism analysis evidenced that in Zn(OTf)_(2) electrolyte,Zn^(2+) intercalation in the first discharge process promoted K_(2) V_6 O_(16)·1.5 H_(2) O nanofibers to transform into Zn_(3+x)V_(2) O_7(OH)_(2)·2 H_(2) O nanoflakes,and the latter served as the Zn^(2+)-storage host in subsequent charge/discharge processes.Benefiting from open-framework crystal structure and sufficiently exposed surface,the Zn_(3+x)V_(2) O_7(OH)_(2)·2_H2 O nanoflakes exhibited high Zn^(2+) diffusion coefficient,smaller charge-transfer resistance and good reversibility of Zn^(2+) intercalation/de-intercalation,thus leading to superior electrochemical performance.While in ZnS04 aqueous electrolyte,the cathode material cannot sufficiently transform into Zn_(3+x)V_(2) O_7(OH)_(2)·2 H_(2) O thereby corresponding to inferior electrochemical behaviors.Underlying mechanism and influencing factors of such a transformation phenomenon was also explored.This work not only reports a high-performance ZIB cathode material based on electrochemically induced transformation of vanadium oxides,but also provides new insights into Zn^(2+)-storage electrochemistry.

The pharmacokinetic study of rutin in rat plasma based on an electrochemically reduced graphene oxide modified sensor

An electrochemical method based on a directly electrochemically reduced graphene oxide （ERGO） film coated on a glassy carbon electrode （GCE） was developed for the rapid and convenient determination of rutin in plasma. ERGO was modified on the surface of GCE by one-step electro-deposition method. Electrochemical behavior of rutin on ERGO/GCE indicated that rutin underwent a surface-controlled quasi-reversible process and the electrochemical parameters such as charge transfer coefficient （α）, electron transfer number （n） and electrode reaction standard rate constant （ks） were 0.53, 2 and 3.4 s -1, respectively. The electrochemical sensor for rutin in plasma provided a wide linear response range of 4.70 × 10 ^-7 1.25 × 10^-5 M with the detection limit （s/n=3） of 1.84 × 10^-8 M. The assay was success- fully used to the pharmacokinetic study of rutin. The pharmacokinetic parameters such as elimination rate half-life （t1/2）, area under curve （AUC）, and plasma clearance （CL） were calculated to be 3.345 ± 0.647 rain, 5750 ±656.0 μg min/mL, and 5.891± 0.458 mL/min/kg, respectively. The proposed method utilized a small sample volume of 10 μL and had no complicated sample pretreatment （without deproteinization）, which was simple, eco-friendly, and time- and cost-efficient for rutin pharmacokinetic studies.

Continuous Separation of Cesium Based on NiHCF/PTCF Electrode by Electrochemically Switched Ion Exchange

Nickel hexacyanoferrate (NiHCF) film was synthesized on porous three-dimensional carbon felt (PTCF) substrate by repetitious batch chemical depositions, and the NiHCF/PTCF electrode was used as electrochemically switched ion exchange (ESIX) electrode in a packed bed for continuous separation for cesium ions. The morphologies of the prepared electrodes were characterized by scanning electron microscopy and the effects of solution concentration on the ion-exchange capacity of the electrodes were investigated by cyclic voltammetry technique. Cycling stability and long-term storage stability of NiHCF/PTCF electrodes were also studied. The NiHCF/PTCF electrodes with excellent ion-exchange ability were used to assemble a diaphragm-isolated ESIX reactor for cesium separation. Continuous separation of cesium and regeneration of NiHCF/PTCF electrode based on the diaphragm-isolated reactor were performed in a laboratory-scale two-electrode system.

Electrodeposited iodide ions imprinted polypyrrole@bismuth oxyiodide film for an electrochemically switched renewable extractor towards iodide ions

Effective extraction and regeneration of radioactive iodide is one of urgent concerns for the safe utilization of nuclear energy.As a novel environmentally benign ion separation technique,electrochemically switched ion extraction(ESIE)process can be applied for effective capture and recovery of iodide ions(I^(-)).Herein,a novel kelp seaweed-like core/shell I^(-)imprinted polypyrrole@bismuth oxyiodide(PPy/I^(-)@BiOI)composite film is successfully prepared for the selective I^(-)capture in the ESIE system.It is found that the I^(-)can be easily trapped in the PPy/I^(-)@BiOI film after I^(-)is in situ desorbed from the film by an electrochemical reduction process since it offers particular electroactive binding sites for I^(-)extraction.The I^(-)imprinted PPy/I^(-)@BiOI film displays an extraction capacity as high as 325.2 mg·g^(-1)for I^(-)with favorable stability.In particular,the extraction and desorption of I^(-)is achieved by adjusting the redox potential and the pristine PPy/I^(-)@BiOI film can be regenerated and reused for multiple times without decrease in extraction capacity.It is expected that such a PPy/I^(-)@BiOI film would be useful as an electrochemically switched renewable extractor that could capture and regenerate I^(-)from radioactive water.

Enhanced photocatalytic activity of electrochemically synthesized aluminum oxide nanoparticles

In this study, aluminum oxide （Al2O3） nanoparticles （NPs） were synthesized via an electrochemical method. The effects of reac- tion parameters such as supporting electrolytes, solvent, current and electrolysis time on the shape and size of the resulting NPs were investi- gated. The Al2O3 NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis/differential thermal analysis, energy-dispersive X-ray analysis, and ultraviolet-visible spectroscopy. Moreover, the Al2O3 NPs were explored for photocatalytic degradation of malachite green （MG） dye under sunlight irradiation via two processes： ad- sorption followed by photocatalysis; coupled adsorption and photocatalysis. The coupled process exhibited a higher photodegradation effi- ciency （45%） compared to adsorption followed by photocatalysis （32%）. The obtained kinetic data was well fitted using a pseudo-first-order model for MG degradation.

Degradation of chlorophenol by in－situ electrochemically generated oxidant

A novel in-situ electrochemical oxidation method was applied to the degradation of wastewater containing chlorophenol. Under oxygen sparging, the strong oxidant, hydrogen dioxide, could be in-situ generated through the reduction of oxygen on the surface of the cathode. The removal rate ofchlorophenol could be increased 149% when oxygen was induced in the electrochemical cell. The promotion factor was estimated to be about 82.63% according to the pseudo-first-order reaction rate constant (min^-1). Important operating parameters such as current density, sparged oxygen rate were investigated. Higher sparged oxygen rate could improve the degradation of chlorophenol. To make full use of oxygen, however, sparged oxygen rate of 0.05 m3/h was adopted in this work. Oxidation-reduction potential could remarkably affect the generation of hydrogen peroxide. It was found that the removal rate of chlorophenol was not in direct proportion to the applied current density. The optimum current density was 3.5 mA/cm^2 when initial chlorophenol concentration was 100 mg/L and sparged oxygen rate was 0.05 m^3/h.

Electrochemical determination of an anti-hyperlipidimic drug pitavastatin at electrochemical sensor based on electrochemically pre-treated polymer film modified GCE

An electrochemically pretreated silver macroporous(Ag MP) multiwalled carbon nanotube modified glassy carbon electrode(PAN-Ag MP-MWCNT-GCE) was fabricated for the selective determination of an antihyperlipidimic drug, pitavastatin(PST). The fabricated electrochemical sensor was characterized by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). The fabricated electrode was employed in quantifying and determining PST through differential pulse adsorptive stripping voltammetry(DPAdSV) and CV. The electrode fabrication proceeded with remarkable sensitivity to the determination of PST. The effect of various optimized parameters such as pH, scan rate(ν), accumulation time(t_(acc)), accumulation potential(U_(acc))and loading volumes of Ag MP-MWCNT suspension were investigated to evaluate the performance of synthesized electrochemical sensor and to propose a simple, accurate, rapid and economical procedure for the quantification of PST in pharmaceutical formulations and biological fluids. A linear response of PST concentration in the range 2.0×10^(-7)–1.6×10^(-6)M with low detection(LOD) and quantification(LOQ) limits of 9.66 ± 0.04 nM and 32.25 ± 0.07 nM, respectively, were obtained under these optimized conditions.

Electrochemically-driven interphase conditioning of magnesium electrode for magnesium sulfur batteries

The earth-abundant magnesium metal is a kind of promising anode material due to its low reduction potential (-2.356V vs. SHE), high volumetric and gravimetric specific capacities of 3882 mAh cm-3 and 2234 mAh g_1 respectively [1]. Moreover, the magnesium anode shows high safety due to the non-dentritic electrodeposition mechanism during cycling, which is related to the strong Mg-Mg bonding and the consequent high energy barrier between the crystal boundaries of different crystal orientation [2].

Heterostructure Solar Cells Based on Sol-Gel Deposited SnO₂and Electrochemically Deposited Cu₂O

To fabricate a heterostructure solar cell using environmentally friendly materials and low cost techniques, tin oxide (SnO2) and cuprous oxide (Cu2O) were deposited by the sol-gel method and the electrochemical deposition, respectively. The SnO2 films were deposited from a SnCl2 solution containing ethanol and acetic acid. The Cu2O films were deposited using a galvanostatic method from an aqueous bath containing CuSO4 and lactic acid at a temperature of 40°C. The Cu2O/SnO2 heterostructure solar cells showed rectification and photovoltaic properties, and the best cell showed a conversion efficiency of 6.6 × 10-2 % with an open-circuit voltage of 0.29 V, a short-circuit current of 0.58 mA/cm2, and a fill factor of 0.39.

Electrochemically Reduced Graphene Oxide as Modified Electrode Material for Determination of Dihydroxybenzenes

A simple and green method was introduced to fabricate the electrochemical sensor based on the electrochemically reduced graphene oxide（ERGO） modified electrode. It was found that the ERGO modified electrode exhibited an excellent catalytic activity toward the oxidation of dihydroxybenzenes isomers. Under the optimum conditions, in the simultaneous determination of the dihydroxybenzene isomers, the currents were linear with the concentrations of the isomers from 5 to 550 μmol/L for hydroquinone（HQ）, from 6 to 400 μmol/L for catechol（CT） and from 5 to 350 μmol/L for resorcinol（RS）, respectively. In addition, the proposed sensor has good stability and reproducibility. The developed method has been applied to the simultaneous determination of dihydroxybenzene isomers in real samples with a satisfactory recovery from 98% to 103%.

CVD SiC Fiber Electrochemically Treated by AC Current

The tensile strength of CVD SiC fiber was remarkably improved by electrochemical surface treatment. SEM analyses reveal that AC current treatment could form a more compact and complete SiO2 layer than DC current on the surface of the SiC fiber, which was beneficial to the improvement of tensile strength. It was also verified that AC current was more effective for producing high performance SiC fiber with SiO2 surface layer than DC current. The frequency is a sensitive parameter for the process; but the signals of input current had relatively small effect on the tensile strength of SiC fiber. A further discussion for this phenomenon was completed. The proposed operational parameters are 0.3 A, 5 kHz of sine wave and 91 m/h of the receiving rate respectively.

SiO2 stabilizes electrochemically active nitrogen in few-layer carbon electrodes of extraordinary capacitance

Pyrrolic and pyridinic N dopants can dramatically increase the electrochemical activities of carbon and conducting polymers.Although N-doped conducting polymers suffer from rapid degradation,their carbon counterpart of extraordinary capacitance has remarkable rate performance and cycling endurance thanks to carbon’s excellent electrical conductivity.But high nitrogen content and high electrical conductivity are difficult to achieve in a high-surface-area carbon,because the high chemical vapor deposition(CVD)temperature required for obtaining high conductivity also destabilizes under-coordinated pyrrolic and pyridinic nitrogen and tends to lower the surface area.Here we resolve this dilemma by using SiO2 as an effective N-fixation additive,which stabilizes the N-rich nano few-layer sp2-carbon construct in1000℃CVD.This enables a scalable sol-gel/CVD fabrication process for few-layer carbon electrodes of extraordinary capacitance(690 F g^-1).The electrodes have excellent rate performance and can maintain90%of their initial capacitance after 30,000 cycles,thus potentially suitable for practical applications.

Photoactive area modification in bulk heterojunction organic solar cells using optimization of electrochemically synthesized ZnO nanorods

In this work, ZnO nanorod arrays grown by an electrochemical deposition method are investigated. The crucial parameters of length, diameter, and density of the nanorods are optimized over the synthesize process and nanorods growth time. Crystalline structure, morphologies, and optical properties of ZnO nanorod arrays are studied by different techniques such as x-ray diffraction, scanning electron microscope, atomic force microscope, and UV-visible transmission spectra. The ZnO nanorod arrays are employed in an inverted bulk heterojunction organic solar cell of Poly （3-hexylthiophene）：[6- 6] Phenyl-（6） butyric acid methyl ester to introduce more surface contact between the electron transporter layer and the active layer. Our results show that the deposition time is a very important factor to achieve the aligned and uniform ZnO nanorods with suitable surface density which is required for effective infiltration of active area into the ZnO nanorod spacing and make a maximum interfacial surface contact for electron collection, as overgrowing causes nanorods to be too dense and thick and results in high resistance and lower visible light transmittance. By optimizing the thickness of the active layer on top of ZnO nanorods, an improved efficiency of 3.17% with a high FF beyond 60% was achieved.

Monitoring of Anthocyanins and Colour in Electrochemically Processed <i>Hibiscus sabdariffa</i>Juice

The vital role of anthocyanins in Hibiscus sabdariffa L. is now known to most consumers. The richness of anthocyanins in antioxidants, vitamin C, minerals, etc., provides Hibiscus juice with proven nutritional qualities. The health requirements of recent years have made food products with added preservatives or processed at high temperatures less popular, thus explaining the new orientations towards innovative and interdisciplinary technologies. Anthocyanins from Hibiscus sabdariffa L. are, however, sensitive to degradation factors such as temperature, light, enzymes and also oxygen. The instability of anthocyanins has long been a subject of research using classic techniques such as heat treatment, the results of which are often limited by the rapid degradation and above all the destruction of the nutritional and organoleptic qualities of the product. Oxygen dissolved in juices is so far treated by bubbling with an inert gas or by adding other molecules such as preservatives which can cause a lot of health damage. The electrochemical approach is a new stabilisation technique that reduces the dissolved oxygen in the juice, cold and without the addition of other molecules. The electrolysis of Hibiscus juice was carried out by noble electrodes (Platinum and Stainless Steel) with a well-characterised Time/Potential or Time/Intensity couple. The electroreduced samples and the control were then stored at 4°C, 25°C and 37°C for more than 6 months. Monitoring of anthocyanins in the first month, of the samples and the control, showed a significant difference of 10% between the electroreduced extract and the untreated control at 37°C, which had previously been problematic for the heat treatment and even for the other membrane techniques. Oxygen reduction on the platinum electrode/ECS allowed the retention of more than 10% of anthocyanins after 4 weeks of storage at 25°C and 37°C. At 4°C, a significant difference of 5% between the electro-reduced Hibiscus juice and the control was maintained until the fifth month of storage with the 1/5 ratio (calyx/water). Non-significant losses in anthocyanin (10 mg/l), for the juice with reduced dissolved oxygen, were noted for the 1/5 and 1/15 ratios during the first month of storage at 4°C against 24 mg/l of significant losses for the 1/20 ratio. However, the untreated control showed significant losses for the ratios 1/20, 1/15 and 1/5. Oxygen dissolved in the juice therefore considerably degrades the anthocyanins of Hibiscus sabdariffa L. from the first month of storage at 4°C.

Graphene Oxide/Multilayer-Graphene Synthesized from Electrochemically Exfoliated Graphite and Its Influence on Mechanical Behavior of Polyurethane Composites

Graphene Oxide/Multilayer-Graphene (GO-MG) flakes were obtained using an electrochemically exfoliated graphite (GR) electrode from secondary steel-making industry performed in a two-electrode system using tungsten as the counter electrode and GR as the working electrode. The exfoliated GO-MG flakes were processed and incorporated in an elastomeric polyurethane (PU) matrix. The mechanical properties of the PU/GO-MG composites were evaluated and compared with equivalent composites made of PU/GR powder. From experimental data analysis it was concluded that GO-MG flakes were approximately composed of 67 wt% GO and 33 wt% MG. The number of layers in the graphene flakes was estimated to be between 2 and 5 sheets. PU showed a breaking stress of 570 kPa, while the PU/20wt% GR attained a maximum stress of 750 kPa as compared to PU/10wt% GO-MF composite exhibiting a breaking stress of 1060 kPa.

An Investigation on Kinetics of Photo Catalysis, Characterization, Antibacterial and Antimitotic Property of Electrochemically Synthesized ZnS and Nano Photocatalysts

Zinc sulphide is one of the commercially important II-VI semiconductors having a wide band gap, rendering it a very attractive material for optical application especially in nanocrystalline form. Nanocomposites of ZnS and ZrS2/ZnS were prepared by simple electrochemical method;their photocatalytic properties had been investigated. The structure, composition and optical property of the product were characterized by X-ray diffraction (XRD), FE-SEM (EDAX), UV-VIS and IR techniques. The UV-VIS spectra exhibited a blue-shift with respect to that of bulk material due to quantum confinement effect. Kinetics of photocatalytic degradation of Indigo Carmine dye has been studied. The photocatalytic decolourization of the dye follows first order kinetics. The antimitotic and antibacterial activity of these nanoparticles was investigated.