RESUMEN

In this paper, we outline the development of stoichiometric chalcostibite, CuSbS2 thin films, from a single bath by pulse electrodeposition for its application as a photocathode in photoelectrochemical cells (PEC). The Cu/Sb precursor molar ratio of the deposition bath was varied to obtain stoichiometric CuSbS2 thin films. The optimized deposition and dissolution potentials were -0.72 V and -0.1 V vs saturated calomel electrode, respectively. The formation of CuSbS2 was analyzed using different characterization tools. X-ray diffraction and Raman results showed the formation of the pure chalcostibite phase from a precursor bath with molar ratio Cu/Sb = 0.41. The heterostructure CuSbS2/CdS/Pt was tested as a photocathode in the PEC. The energy positions of the conduction and valence bands were estimated from the Mott Schottky plots. The conduction band and valence band offset of CuSbS2/CdS heterojunction were 0.1 eV and 1.04 eV, respectively. The electric field created in the junction reduced the recombination of the electron/hole pairs and improved charge transfer in the interface. The heterostructure CuSbS2/CdS/Pt demonstrated an improved photocurrent density of 3.4 mA cm-2 at 0 V vs reversible hydrogen electrode. The PEC efficiency obtained from the CuSbS2/CdS heterojunction was 0.56 %. Therefore, we demonstrated the feasibility of an inexpensive technique like electrodeposition for the development of an efficient earth-abundant photocathode.

RESUMEN

In order to increase the hardness, wear resistance and corrosion resistance of nickel-based coatings, pure nickel is often co-electrodeposited with silicon carbide (SiC) particles. However, SiC particles tend to agglomerate and precipitate in the bath, which reduces the amounts of nanoparticles and causes nonuniformity. Herein, we solve these problems by using binary non-ionic surfactants (Span 80 and Tween 60) to effectively disperse SiC particles (binary-SiC) in the bath, which suppresses nanoparticles agglomeration and leads to uniformly distributed SiC particles in the composite coatings. In comparison to the Ni/SiC coatings electrodeposited from the commonly used SDS-modified SiC, the coatings prepared with binary-SiC (Ni/binary-SiC) show finer crystallization and a smoother surface. In addition, the Ni/binary-SiC coatings exhibit higher hardness (556 Hv) and wear resistance (2.95 mg cm-2). Furthermore, higher corrosion resistance is also achieved by the Ni/binary-SiC coatings.

RESUMEN

The effect of the applied potential on the crystallography, morphology, optical, and electrical properties of copper-cobalt oxide (Cu2CoO3) co-electrodeposited on ITO (Indium Tin Oxide) substrate has been studied. The electrochemical behavior of Cu2CoO3 using cyclic voltammetry showed that the co-electrodeposition of Cu2CoO3 occurred at a negative potential of - 0.70 V versus SCE, following a quasi-reversible reaction controlled by the diffusion process. Chronoamperometry (CA) revealed that the nucleation and growth mechanism of Cu2CoO3 follows the instantaneous three-dimensional process according to Scharifker and Hill model. X-ray diffraction (XRD) analysis indicated that the resulting layers at different applied potentials exhibited an orthorhombic structure with a preferred orientation of the crystallites (011) plan. The morphology of the surface changes with potential applied. Furthermore, the optical properties of the copper and cobalt oxide films were investigated using UV-visible spectroscopy; showing that the band gap energy for all the materials increases when the applied potential decreases. The Cu2CoO3 layers obtained are p-type semiconductors. The acceptor density (NA) increases with decreasing applied potential.

RESUMEN

Electrochemical reduction of CO2 to fuels and chemicals is an effective way to reduce greenhouse gas emissions and alleviate the energy crisis, but the highly active catalysts necessary for this reaction under mild conditions are still rare. In this work, we grew CuBi bimetallic catalysts on derived copper foam substrates by co-electrodeposition, and then investigated the correlation between co-electrodeposition potential and electrochemical performance in CO2-to-formate conversion. Results showed that the bimetallic catalyst formed at a low potential of - 0.6 V vs. AgCl/Ag electrode achieved the highest formate Faradaic efficiency (FEformate) of 94.4% and a current density of 38.5 mA/cm2 at a low potential of - 0.97 V vs. reversible hydrogen electrode (RHE). Moreover, a continuous-flow membrane electrode assembly reactor also enabled the catalyst to show better performance (a FEformate of 98.3% at 56.6 mA/cm2) than a traditional H-type reaction cell. This work highlights the vital impact of co-electrodeposition potential on catalyst performance and provides a basis for the modulated growth of bimetallic catalysts on substrates. It also shows the possibility of preparing Bi-based catalysts with no obvious decrease in catalytic activity that have been partially replaced with more economic copper.

RESUMEN

This study presents a sensitive approach for electrochemical determination of 5-hydroxymethylfurfural (5-HMF) in food. The electrochemical sensor was fabricated on a copper electrode (CuE) modified with co-electrodeposited Cu-Ni bimetallic particles. This sensor, fabricated by 30 cycles of cyclic voltametric scanning with a scan rate of 50 mV s-1, exhibits good electrocatalytic ability to 5-HMF oxidation. Under the optimal conditions, linear scan voltammetry (LSV) and chronoamperometry were conducted for the determination of 5-HMF. The results of LSV show that a linear dependency within the 0.4-10 mM range with a detection limit (LOD) of 3.51 µM (S/N = 3) was achieved, while a linear range in 1 × 10-4-11 mM with a LOD of 0.043 µM (S/N = 3) was obtained by chronoamperometric measurement. The electrochemical sensor was finally applied in determination of 5-HMF in various foods, and the reliability and accuracy of the method were assessed by adopting an UV method as a standard method. Results show that the concentrations of 5-HMF in real samples are close to those measured by the standard method. In addition, standard addition method was further performed to evaluate the accuracy of our approach. The recoveries ranged from 90.0% to 110.0% are calculated, demonstrating good accuracy of the electrochemical sensor.

Asunto(s)

Cobre , Técnicas Electroquímicas , Electrodos , Furaldehído/análogos & derivados , Límite de Detección , Reproducibilidad de los Resultados

RESUMEN

Although various processes for metal printing at the micro- and mesoscale have been demonstrated, printing functional devices such as thermocouples, thermopiles, and heat flux sensors that function based on interfaces between an alloy and another alloy/metal demands processes for printing alloys. Furthermore, a high-quality and crystalline alloy is required for acceptable function of these devices. This article reports for the first time co-electrodeposition-based printing of single-phase solid solution nanocrystalline copper/nickel (Cu/Ni) alloy with various controllable compositions (Cu100Ni0 to Cu19Ni81) from a single electrolyte. The printed alloy is nanocrystalline (<35 nm), continuous, and dense with no apparent porosity, with remarkable mechanical and magnetic properties, without any postprocessing annealing such as heat treatment. In addition, a functional thermocouple fabricated using this process is demonstrated. Such a process can not only be used for fabrication of functional devices, it may also facilitate fundamental studies on alloys by printing a continuous library of alloy composition for material characterization.

RESUMEN

A novel bismuth (Bi)-biopolymer (chitosan) nanocomposite screen-printed carbon electrode was developed using a Bi and chitosan co-electrodepositing technique for detecting multiple heavy metal ions. The developed sensor was fabricated with environmentally benign materials and processes. In real wastewater, heavy metal detection was evaluated by the developed sensor using square wave anodic stripping voltammetry (SWASV). The nanocomposite sensor showed the detection limit of 0.1 ppb Zn2+, 0.1 ppb Cd2+ and 0.2 ppb Pb2+ in stock solutions. The improved sensitivity of the Bi-chitosan nanocomposite sensor over previously reported Bi nanocomposite sensors was attributed to the role of chitosan. When used for real wastewater samples collected from a mining site and soil leachate, similar detection limit values with 0.4 ppb Cd2+ and 0.3 ppb Pb2+ were obtained with relative standard deviations (RSD) ranging from 1.3% to 5.6% (n = 8). Temperature changes (4 and 23 °C) showed no significant impact on sensor performance. Although Zn2+ in stock solutions was well measured by the sensor, the interference observed while detecting Zn2+ in the presence of Cu2+ was possibly due to the presence of Cu-Zn intermetallic species in mining wastewater. Overall, the developed sensor has the capability of monitoring multiple heavy metals in contaminated water samples without the need for complicated sample preparation or transportation of samples to a laboratory.

RESUMEN

Copper zinc tin sulfo-selenide (CZTSSe) is a promising light-absorbing material of thin-film solar cells because of its low material cost especially when it is prepared by cost-effective processes like the electrochemical deposition process. The CZTSSe thin-film solar cells, however, suffer from the relatively low efficiency, mostly because of the significant charge recombination. Given that the surface recombination is one of the major recombination paths, controlling the surface roughness, and thus the interfacial area is one of the key factors for improving their device performances. In this study, we demonstrated a simple but effective strategy for reducing the surface roughness during the electrochemical deposition process of the CZTSSe thin films. By adopting an initial nucleation stage with higher deposition currents ahead of the steady-state galvanostatic deposition, the surface of the copper-zinc-tin (CZT) precursor and CZTSSe thin films became significantly smoother and uniform (ΔRrms: -43.8% for CZT, -28.9% for CZTSSe). The effects of the surface roughness on the photovoltaic properties of the CZTSSe thin-film solar cells have been investigated systematically with various characterization techniques like the diode analysis, lifetime measurement, and the temperature dependency of the open-circuit voltage. The device with the smoother surface exhibited higher open-circuit voltage and fill factor, mostly because of the significantly reduced charge recombination, leading to the high conversion efficiency of 8.64% (active).

RESUMEN

Development of highly-active and noble-metal-free electrocatalysts for hydrogen evolution reactions is a challenge, and optimizing the structure and the composition of the relative materials is critical to obtain the high-quality catalysts. Ni-based compounds are being explored as noble-metal-free electrocatalysts in hydrogen evolution reactions but the Ni-based needs to be modified effectively. In this work, we co-electrodeposited Ni nanoparticles, hydrophilic graphene and graphene oxide layers on Ni foam to synthesize Ni-HG-rGO/NF catalysts. It was presented a Datura-like shape allowing for high performance with current densities of -10 and -100 mA cm-2 for HER at overpotentials of -50 and -132 mV, a low Tafel slope of -48 mV dec-1 and excellent long-term stability in 1.0 M NaOH solution. These results demonstrate that the Ni-HG-rGO/NF electrode can be a competitive electrode materials for HER in alkaline conditions.

RESUMEN

Layer-by-layer chitosan-decorated pristine graphene on screen-printed electrodes was achieved by one-step electrodeposition method and an enzyme-free hydrogen peroxide electrochemical biosensor was fabricated for its application. Negatively charged pristine graphene absorbed with positively charged chitosan by electrostatic interactions was electrodeposited on the electrodes. The successful immobilization of pristine graphene was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and electrochemical characterizations. The graphene-chitosan volume ratio and cyclic voltammetry scan cycles during the electrodeposition process were optimized. The resulting hydrogen peroxide biosensors showed a 178 times improved sensitivity and exhibited two wide linear detection ranges from 20 µM to 20 mM and from 20 mM to 60 mM. The biosensors also showed a good reproducibility, stability, selectivity and could be used in real samples detection. The superior electrochemical performance of graphene-chitosan was attributed to the preservation of excellent properties of pristine graphene, and the formation of layer-by-layer structure with high surface area. The proposed strategy of direct immobilization of pristine graphene can be extended for the immobilization of other nanomaterials and biomolecules.

RESUMEN

A facile co-electrodeposition method has been developed to fabricate reduced graphene oxide/polypyrrole (rGO/PPy) composite films, with sodium dodecyl benzene sulfonate as both a surfactant and supporting electrolyte in the precursor solution. The introduction of rGO into the PPy films forms porous structure and enhances the conductivity across the film, leading to superior electrochemical performance. By controlling the deposition time and rGO concentration, the highest area capacitance can reach 411 mF/cm2 (0.2 mA/cm2) for rGO/PPy films, whereas optimized specific capacitance is as high as 361 F/g (0.2 mA/cm2). All of the composite films exhibit excellent rate capability (at least 175 F/g at the current density of 12 mA/cm2) compared with pure PPy film (only 12 F/g at the current density of 12 mA/cm2). The rGO/PPy composite exhibits excellent cycling stability that maintains 104% of its initial capacitance after cycling for 2000 cycles and 80% for 5000 cycles. The two-electrode solid-state supercapacitor (SC) based on rGO/PPy composite electrodes demonstrates good rate performance, excellent cycling stability, as well as a high area capacitance of 222 mF/cm2. The solid-state planar SC based on the rGO/PPy composite exhibits an area capacitance of 9.4 mF/cm2, demonstrating great potential for fabrication of microsupercapacitors.