Cyclic Voltammetric Deposition Research Articles

Cyclic voltammetric deposition of binder-free Ni-Se film on Ni foams as efficient bifunctional electrocatalyst for boosting overall urea-water electrolysis

The development of efficient and low-cost bifunctional electrocatalysts for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) is highly challenging in urea-water-alkali electrolyzers. Herein, nickel-selenium electrocatalysts (denoted as Ni-Se) were controllably grown on Ni foam by a facile and simple cyclic voltammetric electrodeposition for overall urea electrolysis. Considering the good conductivity and high hydrophilic surface of Ni-Se@NF, the optimized Ni-Se electrocatalyst exhibited the eminent HER and UOR catalytic competence. In 1 M KOH with 0.33 M urea electrolyte, Ni-Se electrocatalysts required an overpotential of 181 mV for HER and potential of 1.347 V versus reversible hydrogen electrode for UOR to achieve a current density of 10 mA·cm−2. Additionally, the electrocatalyst showed good durability in both HER and UOR. Moreover, the electrolyzer assembled by Ni-Se electrocatalysts as electrode couple exhibited a remarkable activity with a small cell voltage of 1.41 V to reach 10 mA·cm−2 for overall urea-water electrolysis.

Fabrication of NiCo2S4/nickel foam composite electrodes by cyclic voltammetric deposition and their supercapacitor performance

The NiCo2S4/nickel foam composite electrodes have been fabricated by cyclic voltammetric deposition of NiCo2S4 arrays on nickel foam, and the supercapacitor performance of the composite electrodes has been investigated. The results show that the electrode with 5 deposition cycles has the highest supercapacitor performance. It achieves a specific capacitance of 2244.8 F/g at current density of 1 A/g; it still has a capacitance retention rate of 66 % and a Coulombic efficiency of 99 % after 1000 cycles of charge/discharge.

Construction of MXene–BiVO4–FeOOH composite photoanode with ultra-low onset potential: performance, DFT calculation and mechanism

Synergistic enhancement of carrier separation-transport and acceleration of water oxidation kinetics is an effective way to boost the current density of photoanode. Therefore, in this work, we constructed Ti3C2Tx MXene conductive framework by cyclic voltammetric (CV) deposition within BiVO4 to force carrier separation-transfer while also depositing O-vacancied FeOOH by in situ self-hydrolysis to accelerate water oxidation kinetics. Predictably, the constructed MXene–BiVO4–FeOOH composite photoanode exhibits an impressive current density of 4.95 mA/cm2 (1.23 V vs. RHE) and 4.1 times higher than that of pristine BiVO4, as well as an ultra-low onset potential and high stability. This fantastic enhancement is attributed to the MXene conductive framework avoiding carrier recombination, tightening the interface of BiVO4–FeOOH, moreover O-vacancied FeOOH improves the adsorption of H2O to accelerate the water oxidation kinetics. This work demonstrates a successful method for constructing efficient and stable photoanodes as well as diversifying the application of MXene in photoelectrocatalysis.

Co‐Electrodeposition of Nanostructured Ce‐NiOx on Stainless‐Steel Substrates for the Oxygen Evolution Reaction under Alkaline Conditions

AbstractThe development of cost‐effective catalysts that can be fabricated at scale for electrochemical water oxidation is an ongoing challenge. Here it is shown that stainless‐steel AISI316 is an appropriate support electrode for a co‐electrodeposited Ni‐CeOx catalyst for the oxygen evolution reaction (OER) under alkaline conditions. Optimal OER performance is achieved via a cyclic voltammetric deposition protocol rather than constant potential deposition for the catalyst layer. An overpotential of 300 mV at a current density of 10 mA cm−2 is recorded with a Tafel slope of 43 mV dec−1 while the catalyst also demonstrates long‐term stability. It is also found that the catalyst layer changes significantly after the OER. This includes changes to the catalyst morphology, distribution of oxidation state, and speciation as well as the transformation from an entirely amorphous material into one containing crystalline regions. This simple one‐step electrodeposition process on a cost‐effective substrate should, in principle, facilitate the fabrication of low‐cost electrolyzers.

Sensitization of TiO2 nanotube arrays photoelectrode via homogeneous distribution of CdSe nanoparticles by electrodeposition techniques

CdSe has attracted interest as the absorber layer in photoelectrochemical cell applications. In this work, titania nanotubes thin film electrodes were prepared by the anodisation method of titanium foil were used due to their ability to produce a uniformly stable structure with high surface area, excellent charge transfer, low interfacial grain boundaries and effective absorption of light. Three electrochemical deposition techniques were used to deposit CdSe onto TiO2 NTAs, namely potentiostatic deposition, cyclic voltammetric deposition, and pulse electrodeposition techniques as a novel to compare between these methods. X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), and UV–Visible diffuse reflectance spectroscopy were used for the characterization of CdSe/TiO2 NTAs nanostructures. The photoelectrochemical performance of the nanostructured CdSe/TiO2 NTAs was investigated in 0.01 M Na2S under visible light illumination. The use of pulse electrodeposition resulted in a greater uniformity in the distribution of CdSe loaded onto TiO2 nanotube arrays. Thus the performance of semiconductor heterostructures prepared by this technique shows a substantial improvement compared to the other two techniques.

10 μm-thick MoO3-coated TiO2 nanotubes as a volume expansion regulated binder-free anode for lithium ion batteries

In this study, 10μm-thick TiO2 nanotube arrays (TNAs) coated with a MoO3 layer were prepared by electrochemical oxidation on titanium foil followed by successive cyclic voltammetric deposition, aiming at the fabrication of a thick binder-free anode with high capacity and good cycling stability for lithium ion batteries (LIBs). Through the evaluation of the electrochemical performance of electrodes prepared under various conditions, the electrode obtained at a precursor concentration of 5mM showed the best electrochemical performance, exhibiting high reversible capacity and enhanced cycling stability. With the structural advantage and intrinsic characteristics of TNAs, the large volume expansion of MoO3 is successfully accommodated, resulting in 97% retention at a rate of 5 C over 500 cycles and 91% retention even at a high rate of 25 C.

Electrochemically Fabricated Ni−P, Ni−S and Ni−Se Materials for Overall Water Splitting: Investigating the Concept of Bifunctional Electrocatalysis

AbstractTransition‐metal‐based electrocatalysts containing chalcogenides (S and Se) or phosphorous have been extensively reported as bifunctional electrocatalysts for overall water splitting. However, there remains the question as to whether the pristine material is truly bifunctional with regards to inherent activity for both the hydrogen evolution reaction (HER) and the oxygen evolution (OER), which has implications for their use in commercial electrolyzers when coupled with renewable energy sources. Herein, we present a case study on electrochemically synthesized NiSx, NiPx and NiSex films by using a cyclic voltammetric deposition technique. The HER and OER performances of these electrocatalysts were evaluated in 1 M NaOH, where good activity was observed. Post‐OER catalysis analysis with scanning electron microscopy and X‐ray photoelectron spectroscopy revealed that structural changes are limited to the surface of the materials, but that extensive oxidation occurs. Subsequent HER experiments revealed a significant deterioration in performance in all cases. This raises the question if materials of this type in their pristine state can truly be regarded as bifunctional for overall electrochemical water splitting?

Nickel-foam-supported ruthenium oxide/graphene sandwich composite constructed via one-step electrodeposition route for high-performance aqueous supercapacitors

A high-performance supercapacitor both considered high power and high energy density is needed for its applications such as portable electronics and electric vehicles. Herein, we construct a high-performance ruthenium oxide/graphene (RuO2-ERG) composite directly grown on Ni foam through cyclic voltammetric deposition process. The RuO2-ERG composite with sandwich structure is achieved effectively from a mixed solution of graphene oxide and ruthenium trichloride in the −1.4 V to 1.0 V potential range at a scan rate of 5 mV s−1. The electrochemical performance is optimized by tuning the concentration of the ruthenium trichloride. This integrative RuO2-ERG composite electrode can effectively maintains the accessible surface for redox reaction and stable channels for electrolyte penetration, leading to an improved electrochemical performance. Symmetrical aqueous supercapacitors based on RuO2-ERG electrodes exhibit a wider operational voltage window of 1.5 V. The optimized RuO2-ERG electrode displays a superior specific capacitance with 89% capacitance retention upon increasing the current density by 50 times. A high energy density of 43.8 W h kg−1 at a power density of 0.75 kW kg−1 is also obtained, and as high as 39.1 W h kg−1 can be retained at a power density of 37.5 kW kg−1. In addition, the capacitance retention is still maintained at 92.8% even after 10,000 cycles. The excellent electrochemical performance, long-term cycle stability, and the ease of preparation demonstrate that this typical RuO2-ERG electrode has great potentialities to develop high-performance supercapacitors.

Determination of methimazole based on electropolymerized-molecularly imprinted polypyrrole modified pencil graphite sensor

Preparation of a molecularly imprinted polymer (MIP) film and its recognition property for methimazole (MMZ) was investigated. The polypyrrole (PPy) film was prepared by the cyclic voltammetric deposition of pyrrole in the presence of a supporting electrolyte (NaClO4·H2O) with and without MMZ through on a pencil graphite electrode (PGE). A computational study based on density functional theory was developed to evaluate the template-monomer geometry and interaction energy in the prepolymerization mixture. The performance of MIP sensor and non-imprinted polymer (NIP) film was evaluated by differential pulse voltammetry (DPV). The most important parameters controlling the performance of sensor were investigated and optimized. The prepared electrode was used for MMZ measurement by a three-step procedure, including analyte extraction in the electrode, electrode washing and electrochemical measurement of MMZ. The molecularly imprinted film exhibited a high selectivity and sensitivity toward methimazole in the experimental conditions. The calibration curve demonstrated linearity over a concentration range of 0.007–6mM with a correlation coefficient (r2) of 0.9808. The accuracy of the method was studied through spiking blank samples showed recovery of 98% with precision of 4%. Limit of detection based on S/N=3 was obtained 3×10−6M. The proposed sensor was applied successfully to determine MMZ in biological model samples and pharmaceuticals.

Sponge-like nickel phosphide–carbon nanotube hybrid electrodes for efficient hydrogen evolution over a wide pH range

Cost-effective hydrogen production via electrolysis of water requires efficient and durable earth-abundant catalysts for the hydrogen evolution reaction (HER) over a wide pH range. Herein, we report sponge-like nickel phosphide–carbon nanotube (Ni x P/CNT) hybrid electrodes that were prepared by facile cyclic voltammetric deposition of amorphous Ni x P catalysts onto the threedimensional (3D) porous CNT support. These compounds exhibit superior catalytic activity for sustained hydrogen evolution in acidic, neutral, and basic media. In particular, the Ni x P/CNT electrodes generate cathodic currents of 10 and 100 mA·cm−2 at overpotentials of 105 and 226 mV, respectively, in a 1 M phosphate buffer solution (pH = 6.5) with a Tafel slope of 100 mV·dec−1; the currents were stable for over 110 h without obvious decay. Our results suggest that the 3D porous CNT electrode supports could serve as a general platform for earth-abundant HER catalysts for the development of highly efficient electrodes for hydrogen production.

Amorphous oxygen-rich molybdenum oxysulfide Decorated p-type silicon microwire Arrays for efficient photoelectrochemical water reduction

We report the fabrication of p-type silicon (Si) photocathodes consisting of well-ordered Si microwire (Si-MW) arrays coupled with non-precious and earth-abundant amorphous oxygen-rich molybdenum oxysulfide (MoOxSy) as both a hydrogen evolution catalyst and a passivation layer. The MoOxSy is conformally grown on the Si-MW surface through photo-assisted cyclic voltammetric (CV) deposition. By adjusting the cycle numbers of the CV deposition, Si-MW array electrodes with different MoOxSy catalyst loadings (Si-MWs@MoOxSy) have been obtained and comprehensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman and Fourier-transform infrared spectroscopies. The photoelectrochemical performance of the Si-MWs@MoOxSy cathodes toward water reduction is investigated and compared with that of platinum nanoparticle decorated Si-MW array electrodes (Si-MWs@PtNPs). An optimized Si-MWs@MoOxSy photocathode is found to exhibit activity comparable to that of the Si-MWs@PtNPs one, with a much better stability in acidic medium. In neutral electrolyte, Si-MWs@MoOxSy outperforms Si-MWs@PtNPs in terms of both activity and stability. Given the low materials cost, easy and well-established electrode fabrication procedure, and high demonstrated photoelectrochemical performance, the Si-MWs@MoOxSy arrays reported here hold substantial promise for use as low-cost and efficient photocathodes for water reduction.

Cyclic voltammetric deposition of discrete nickel phosphide clusters with mesoporous nanoparticles on fluorine-doped tin oxide glass as a counter electrode for dye-sensitized solar cells

Largely spaced Ni5P4 nanoclusters are grown on FTO glass using cyclic voltammetric deposition which includes anodic dissolution of Ni-rich regions following the cathodic deposition, leading to a better activity than Pt in the I−/I3− electrolyte.

Cyclic Voltammetric Deposition of Poly(pyrrole-co-2-formylpyrrole)–Multiwall Carbon Nanotube Composite for Highly Specific Capacitive Electrodes

Abstract A supercapacitor composite electrode was effectively fabricated by using cyclic voltammetric deposition of poly(pyrrole-co-2-formylpyrrole)–multiwall carbon nanotube composite, P(Py-co-FPy)–MWCNT. The charge storage of the three-dimensional nanofibril of the P(Py-co-FPy)-coated MWCNT composite electrode was excellent and reached the specific capacitive value of up to 535 F g−1.

Electrochemical evaluation of troponin T imprinted polymer receptor

The selective detection and quantification of macromolecular targets is a fundamental biological mechanism in nature. Molecularly imprinted polymers (MIPs) have been identified as one of the most promising synthetic alternatives to bioreceptors. However, expanding this methodology towards selective recognition of bulky templates such as proteins appears to be extremely challenging due to problems associated with removal of the template from the polymeric network. In this study, polymer imprinted with troponin T (TnT) was assessed using electrochemical methods and the influence of various extraction methods, including conventional immersion extraction, thermal annealing and ultrasonic-assisted extraction, on the binding characteristics of the troponin-to-imprinted polymer receptor was elucidated. Cyclic voltammetric deposition of o-phenylenediamine (o-PD) film in the presence of TnT as a template was performed in acetate buffer (0.5M, pH 5.2) on a gold substrate. Solvent extraction of the target molecule was optimised and followed by subsequent washing with water. The electrochemistry of a ferro/ferricyanide probe was used to characterise the TnT MIP receptor film. The incubation of the TnT MIP receptor-modified electrode with respect to TnT concentration resulted in a suppression of the ferro/ferricyanide redox current. The dissociation constant (KD) was calculated using a two-site model of template affinity for the TnT MIP receptor. The synthetic TnT MIP receptor had high affinity for TnT with a KD of 2.3×10−13M.

Potentiostatic and cyclic voltammetric deposition of nanostructured manganese oxide for supercapacitor applications

Nanostructured manganese oxide was produced by potentiostatic and cyclic voltammetric deposition techniques from aqueous KMnO4 solutions. Scanning electron microscopy (SEM) and X-ray diffraction were used to study the morphology and crystal structure of the deposited films. The electrochemical properties of deposited films, that obtained by two techniques, were investigated via performing the cyclic voltammetric tests. The results showed the higher specific capacitances of the nanostructured manganese oxide electrodes which have been produced via cyclic voltammetric deposition. The good retention was obtained for all synthesized electrode materials.

Template-Assisted Electrochemical Growth of Hydrous Ruthenium Oxide Nanotubes

We demonstrate that ruthenium oxide () nanotubes with controlled dimensions can be synthesized using facile electrochemical means and anodic aluminum oxide (AAO) templates. nanotubes were formed using a cyclic voltammetric deposition technique and an aqueous plating solution composed of . Linear sweep voltammetry (LSV) was used to determine the effective electrochemical oxidation potential of to . The length and wall thickness of nanotubes can be adjusted by varying the range and cycles of the electrochemical cyclic voltammetric potentials. Thick-walled nanotubes were obtained using a wide electrochemical potential range (-0.2~1 V). In contrast, an electrochemical deposition potential range from 0.8 to 1 V produced thin-walled and longer nanotubes in an identical number of cycles. The dependence of wall thickness and length of nanotubes on the range of cyclic voltammetric electrochemical potentials was attributed to the distinct ionic diffusion times. This significantly improves the ratio of surface area to mass of materials synthesized using AAO templates. Furthermore, this study is directive to the controlled synthesis of other metal oxide nanotubes using a similar strategy.

Amperometric biosensor for NADH and ethanol based on electroreduced graphene oxide–polythionine nanocomposite film

A nanocomposite film is prepared by cyclic voltammetric deposition of electroreduced graphene oxide (ERGO) and polythionine (PTH) on a glassy carbon (GC) electrode. The electrodeposition of ERGO–PTH film is also investigated via the electrochemical quartz crystal microbalance (EQCM) method for more in-depth understanding of the process. The ERGO–PTH nanocomposite film is applied as transducer for facilitated electrocatalytic oxidation of NADH and for the construction of dehydrogenase-based amperometric biosensor. Under optimum conditions, the amperometric detection of NADH provides a wide linear detection range (0.01–3.9mM), a high sensitivity (143μAmM−1cm−2) and a low limit of detection (LOD=0.1μM, S/N=3). With alcohol dehydrogenase (ADH) as a model, we obtain a linear amperometric response of the ADH-modified ERGO–PTH/GC electrode to ethanol concentration from 0.05 to 1.0mM, a sensitivity of 2.8μAmM−1cm−2, and a LOD of 0.3μM (S/N=3).

Morphological and compositional engineering of Ni/carbon nanotube composite film via a novel cyclic voltammetric route

Ni/multi-walled carbon nanotubes (MWCNTs) composite films were deposited on the glassy carbon electrode (GCE) by a Ni plating bath containing homogeneously dispersed MWCNTs using polyvinylpyrrolidone (PVP) as dispersion additive. Incorporation of MWCNTs into Ni matrix was greatly enhanced by the application of cyclic voltammetric (CV) deposition technique. The structure and nature of the Ni/MWCNT were characterized by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD). The results show that the content of MWCNT and the morphology of the deposited Ni/MWCNT composite film can be controlled by selecting the appropriate electroplating conditions. Further study indicates that the obtained Ni/MWCNT showed excellent electro-catalytic activity for the oxidation of ethanol in alkaline solution.

Electrocatalytic Performance of Pd Nanoparticles Supported on SiC Nanowires for Methanol Oxidation in Alkaline Media

AbstractPd nanoparticles (NPs) with a mean size of 10–12 nm are dispersed on the surface of SiC nanowires (NWs) by a cyclic voltammetric deposition method, and employed as an electrocatalyst for methanol oxidation. The high dispersion and small size of supported Pd NPs enable the catalyst to have an electrochemical active surface area of 49.5 m2 g–1, which is larger than that of carbon nanotube supported Pd NPs (38.6 m2 g–1), and that of non‐supported Pd NPs (29.9 m2 g–1). Methanol oxidation measurements show that the supported Pd NPs possess a high electrocatalytic activity and an excellent stability. These results indicate that SiC NWs have great potentials as an advantageous supporting material in alcohol fuel cells.

Bimetallic Pt–Au thin film electrocatalysts with hierarchical structures for the oxidation of formic acid

A series of bimetallic Pt–Au thin films with different Pt/Au ratios were fabricated on glassy carbon (GC) substrates through galvanic replacement reactions between hierarchical Co thin films prepared by cyclic voltammetric deposition and mixed solutions of HAuCl 4 and H 2PtCl 6. The morphologies of the as-prepared Pt–Au thin films resemble those of the sacrificial Co templates, and the Pt/Au ratios in the films are dependent on the HAuCl 4/H 2PtCl 6 molar ratios in the mixed solutions. Because of good stability and excellent synergistic effect of Au and Pt, the bimetallic films with novel structures display unexpected high catalytic activity for the oxidation of formic acid. The as-prepared hierarchical Pt–Au micro/nanostructures are expected to find applications as catalysts in direct formic acid fuel cells (DFAFCs).