Facile Electrochemical Co-deposition Research Articles

The construction of hierarchical PEDOT@MoS2 nanocomposite for high-performance supercapacitor

Hierarchical structural PEDOT@MoS2 nanocomposite is synthesized via a facile electrochemical co-deposition of the intercalation of PEDOT into flower-like MoS2 microspheres. The SEM, TEM, and other characterization results demonstrate the hierarchical PEDOT@MoS2 composite with an enlarged interlayer spacing of MoS2 to 1.02 nm, in which PEDOT nanoparticles act as intercalation, and flower-like MoS2 microspheres are used as a substrate for growth. The electrochemical characterizations indicate that the PEDOT@MoS2 electrode has an ultra-high specific capacitance of 4418 mF cm−2 at 2 mA cm−2 and remarkable cycling stability, retaining 100% of the initial capacitance at a high current density of 100 mA cm−2 after 10,000 cycles. The symmetric PEDOT@MoS2 supercapacitor presents a high energy density of 88.3 mWh cm−2 at 60 mW cm−2, and outstanding cycling stability (93% after 10,000 cycles). These prominent electrochemical performances are attributed to the expanded interlayer spacing, the synergistic effect between PEDOT and MoS2, the low resistance, along with the PEDOT@MoS2 porous structure, indicating great potential applications of the PEDOT@MoS2 electrode in the energy storage field.

Preparation of coaxial Sn-Co alloy/CNFs 3D freestanding membrane anode by electrochemical Co-deposition for lithium-ion batteries

Coaxial Sn-Co alloy/CNFs nanocomposite three-dimensional (3D) membrane is synthesized via a facile electrochemical co-deposition method using the CNFs membrane with 3D network structure as the flexible freestanding substrate. The as-synthesized nanocomposite membrane is characterized using scanning electron microscopy (SEM), transition electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). The results reveal that nanoscaled Sn-Co alloy layer is uniformly covered onto the surface of CNFs; the thickness of Sn-Co alloy shell layer can be controlled to about 60–110 nm. EDS result exhibits that the atomic percentage of Sn, Co, and C in the as-synthesized nanocomposite membrane is 53.25 at%, 20.19 at%, and 26.56 at%, respectively. The nanocomposite membrane with the unique 3D network structure is flexible after Sn-Co alloy deposition. Its electrochemical performances are investigated by the cyclic voltammetry, galvanostatic charge/discharge cycling, and rate cycles. Its discharge specific capacity for 2nd and 50th cycle is 1260 mAh g−1 and 788 mAh g−1, respectively, and the capacity attenuation ratio is about 0.75%/cycle at a current density of 50 mA g−1. The excellent electrochemical performance of the coaxial Sn-Co alloy/CNFs nanocomposite 3D membrane is mainly contributed to the high mechanical strength, good flexibility, and high electrical conductivity of CNFs substrate, which offers a possible solution of Sn volume change and poor electronic conduction during charge/discharge process.

Lithiophobic-lithiophilic composite architecture through co-deposition technology toward high-performance lithium metal batteries

Metallic lithium (Li) has been acclaimed as the most promising anode materials for lithium batteries due to its ultrahigh theoretical capacity of 3860 mA h g−1. Its practical application is impeded, however, due to the notorious problems related to dendrite growth caused by its uneven current density distribution and high Li nucleation overpotential. Here, we report a three-dimensional (3D) lithiophobic phase (Cu) and lithiophilic phase (Zn or Sn) composite architecture realized through a facile electrochemical co-deposition technology and its use as a scaffold for dendrite-free Li metal anode. It is found that the simultaneous formation of this lithiophobic-lithiophilic composite on Cu foam leads to ultrafine lithiophilic phase (20 nm) and reduced Li nucleation overpotential, as well as enhanced homogeneity, which enables a uniform electric field distribution during lithium plating/stripping, thus facilitating even and dendrite-free Li deposition. In the meanwhile, the lithiophobic component in the composite acts as a strong backbone, helping to maintain structural stability during lithium storage. Also, the as-prepared three-dimensional micro/nanoporous scaffold with large surface area can effectively reduce the local current density and suppress Li dendrite growth. The full cells with the composite architecture/Li as anode and LiFePO4 as cathode show promising electrochemical performance with over 80% capacity retention over 1600 cycles at 5 C. This work broadens the horizon of lithiophilic hosts for next-generation high-performance Li metal batteries.

Facile electrochemical co-deposition of metal (Cu, Pd, Pt, Rh) nanoparticles on reduced graphene oxide for electrocatalytic reduction of nitrate/nitrite

Monodispersed metal (Cu, Pd, Pt, Rh) nanoparticles have been anchored on reduced graphene oxide (rGO) by a facile electrochemical co-deposition method. Scanning electron microscopic images reveal the presence of homogeneously dispersed metal nanoparticles on the rGO nanosheets. The as-prepared nanocomposites demonstrate excellent electrocatalytic activity for electroreduction of NO3− and NO2−. The mechanisms associated with the best performed Rh-rGO were studied in detail by cyclic voltammetry, X-ray photoelectron spectroscopic (XPS) and Fourier transformed ac voltammetry. It is proposed that the electrocatalytic reduction of NO3− on Rh-rGO is catalyzed by an adsorbed H* (H+aq + e− → H*) species to form NO2− which is further catalyzed by H* to form a surface confined NO* intermediate. Rh-rGO displays high electrochemical stability for NO3− reduction over the pH range of 4–9, which could be a suitable candidate for applications in remediation of NO3− contamination.

Optimized preparation of core–shell composites based on polypyrrole doped with carbon nanotubes for high performance electrochemical capacitors

Polypyrrole/carbon nanotubes (PPy/CNTs) core–shell composite electrodes have been prepared by facile electrochemical co-deposition. A detailed study regarding the effects of different preparation conditions including electrodeposition mode, parameter, current collector, and carboxylation degree of CNTs on the supercapacitive performances of PPy/CNTs electrodes is carried out. Electrochemical tests suggest a significant effect of current collector on supercapacitive properties of the obtained PPy/CNTs electrodes. Graphite foil as the current collector with low resistance shows remarkably superior capacitive performances relative to FTO conducting glass and ITO conductive plastic. SEM characterizations show galvanostatically deposited PPy/CNTs have a favorable three-dimensional porous nano-network microstructure, while potentiostatically deposited PPy/CNTs present a compact two-dimensional morphology. Furthermore, the CNTs with higher carboxylation degree introduce more PPy, thereby resulting in better electrochemical performances. The optimized PPy/CNTs composite electrodes show a high specific capacitance of 185.3 mF cm−2 at 0.5 mA cm−2, superior rate capability, and outstanding cycling stability (retaining 88.5% of initial capacitance for 10,000 cycles). These results provide a useful orientation to optimize the electrochemical properties of PPy/CNTs core–shell composites applied as electrode material for high performance supercapacitors.

Promoted supercapacitive performances of electrochemically synthesized poly(3,4-ethylenedioxythiophene) incorporated with manganese dioxide

A facile electrochemical codeposition method was developed to prepare the manganese dioxide/poly(3,4-ethylenedioxythiophene) (PEDOT) composite electrodes for supercapacitor applications. Electrode characterizations include Fourier transform infrared spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy, indicating that the MnO2/PEDOT composite is prepared successfully. Electrochemical tests manifest that MnO2/PEDOT composite electrodes have better electrochemical properties than individual MnO2 and PEDOT electrodes. The as-prepared MnO2/PEDOT composite achieves a high areal specific capacitance of 89.7 mF cm−2 at 10 mV s−1, as well as superior rate capability and cycle stability (maintaining 97.1% of initial capacitance for 5000 cycles). The composite we have developed also exhibits superior supercapacitive performances relative to other conducting polymers reported previously, including PEDOT based composite electrodes. These properties of MnO2/PEDOT composite are closely related to the porous microstructures formed and the synergic effect between the two components. The present MnO2/PEDOT based organic–inorganic hybrid materials are very promising for supercapacitor applications.

Facile electrochemical co-deposition of a graphene-cobalt nanocomposite for highly efficient water oxidation in alkaline media: direct detection of underlying electron transfer reactions under catalytic turnover conditions.

A facile electrochemical co-deposition method has been developed for the fabrication of graphene-cobalt nanocomposite modified electrodes that achieve exceptionally efficient water oxidation in highly alkaline media. In the method reported, a graphene-cobalt nanocomposite film was deposited electrochemically from a medium containing 1 mg ml(-1) graphene oxide, 0.8 mM cobalt nitrate and 0.05 M phytic acid (pH 7). The formation of the nanocomposite film was confirmed using electrochemical, Raman spectroscopic and scanning electron microscopic techniques. The nanocomposite film exhibits excellent activity and stability towards water oxidation to generate oxygen in 1 M NaOH aqueous electrolyte media. A turn over frequency of 34 s(-1) at an overpotential of 0.59 V and a faradaic efficiency of 97.7% were deduced from analysis of data obtained by rotating ring disk electrode voltammetry. Controlled potential electrolysis data suggests that the graphene supported catalyst exhibits excellent stability under these harsh conditions. Phytate anion acts as stabilizer for the electrochemical formation of cobalt nanoparticles. Fourier transformed ac voltammetry allowed the redox chemistry associated with catalysis to be detected directly under catalytic turnover conditions. Estimates of formal reversible potentials obtained from this method and derived from the overall reactions 3Co(OH)2 + 2OH(-) ⇌ Co3O4 + 4H2O + 2e(-), Co3O4 + OH(-) ⇌ 3CoOOH + e(-) and CoOOH + OH(-) ⇌ CoO2 + H2O + e(-) are 0.10, 0.44 and 0.59 V vs. Ag/AgCl, respectively.

Facile electrochemical codeposition of “clean” graphene–Pd nanocomposite as an anode catalyst for formic acid electrooxidation

Highly dispersed Pd nanoparticles (NPs) supported on graphene were successfully prepared by a one-step electrochemical codeposition approach. The as-obtained nanocomposite was very “clean” as a result of the reductant-free and surfactant-free synthesis process. The catalyst remarkably improved the electrocatalytic performance for formic acid oxidation (FAO). This facile and controllable method is of significance for the preparation of graphene–metal NPs with desirable catalytic performance.

Selective sensing of cysteine on manganese dioxide nanowires and chitosan modified glassy carbon electrodes

We report a simple approach for the selectively electrochemical sensing of cysteine (CySH) using β-MnO 2 nanowires modified glassy carbon (GC) electrode via a direct and facile electrochemical co-deposition process with chitosan hydrogel. The electrode showed excellent electrocatalytic effect toward cysteine oxidation. A possible reaction mechanism related to the formation of surface complexes was proposed: the –SH group is the reacting group in the reaction between cysteine and MnO 2, while the –NH 2 group acts as an anchor to stabilize the surface complexes. The electrocatalytic behavior is further developed as a sensitive detection scheme for cysteine by amperometric measurement, which shows a large determination range of 0.5–630 μM and a low detection limit of 70 nM. Other nineteen amino acids in a 20-fold concentration do not interfere in the detection of cysteine. Furthermore, other biological species containing –SH group or S S bonds, such as glutathione, cystine, and bovine serum albumin (BSA), show no interferences because of steric hindrance and inactive S S bonds.