Cu-doped MoS 2 thin films were prepared by one-step electrodeposition from 10.0 mM (NH 4 ) 2 MoS 4 , 5.0 mM CuSO 4 , 0.10 M KCl and 0.50 M KSCN at pH 6.95, followed by annealing for three hr. at 500 • C in Ar. Cyclic voltammetry in the presence of the SCNcomplexing agent yields a cathodic deposition peak that is slightly anodically shifted (∼90 mV) relative to the cathodic deposition peaks observed for elecrolytes containing only Cu 2+ and only MoS 4 2− . This may provide evidence for the induced co-deposition mechanism, but it is unclear which specific compound is formed. According to RBS and EDX analysis, thin film deposits contain 1-4 atom% Cu and are sulfur-deficient relative to stoichiometric MoS 2 . Cu dopant incorporation reduces the film resistivity by ∼10x relative to undoped MoS 2 . The specific capacitaqnce of Cu-doped MoS 2 was also measured by both cyclic voltammetry (CV) and galvanostatic charge-dischrarge (GCD). For 500 nm thick annealed MoS 2 films, the specific capacitance of Cu-doped films ranges from 2.5-3.5x higher than that of undoped films during 1000 cycles of CV testing in 1.0 M Na 2 SO 4 . Capacitance testing also reveals better capacity retention and high scan rate performance for Cu-doped relative to undoped MoS 2 films.

Electrochemical methods are attractive for thin film deposition due to their simplicity, conformal and high rate deposition, the ability to easily make multilayers of different composition, ease of scale-up to large surface areas, and applicability to wide variety of different shapes and surface geometries. However, many elements from periodic table of commercial importance are too active to be electrodeposited from aqueous solution. Recent advances are briefly reviewed for room temperature methods for electrochemical deposition, including electrodeposition from ionic liquids, electrodeposition from organic solvents, combined electrodeposition and precipitation on liquid metal cathodes, and galvanic deposition. Recent studies of electrodeposition from ionic liquids include deposition of thick (40 µm) Al coatings on high-strength steel screws in a manufacturing environment; deposition of continuous Si, Ta and Nb coatings; and numerous interesting mechanistic studies. Recent studies of electrodeposition from organic solvents include Al coatings from the AlCl3-dimethylsulfone electrolyte, which demonstrate that additives can be employed to suppress impurity incorporation and to improve the deposit quality, and thick (5-7 µm) and continuous Si coatings from SiCl4 in acetonitrile. Galvanic deposition of Ti, Mo and Si coatings onto Al alloys has recently been reported, which is potentially much simpler and less expensive than electrodeposition from ionic liquids and organic solvents, but has complications associated with substrate consumption and coating adhesion.

We report galvanic deposition of Mo films onto 6061 Al alloy from aqueous solutions containing 1 mM HNO 3 and 10 mM MoCl 5 . Deposition for 40 min. yields an 9 μm thick Mo film, which also contains 18 atom% Al. The corrosion resistance of the Mo film is studied by voltammetry and electrochemical impedance spectroscopy in 0.5 M H 2 SO 4 and in 3.5 wt% NaCl electrolyte at pH 2, 7 and 12. These demonstrate that the galvanic Mo film significantly improves the corrosion resistance of the underlying Al 6061 substrate. Galvanic deposition appears to yield elemental, amorphous Mo films.Mo thin films have many technological applications, including back contacts for photovoltaic devices and corrosion-resistant coatings. 1,2 However, Mo thin film deposition currently requires expensive vacuum methods such as magnetron sputtering. 3 Electrochemical methods for thin film growth are often less expensive, easier to scale-up, and more amenable to high-volume manufacturing than vacuum methods. 4 Electrochemical deposition of refractory metals from aqueous electrolytes is difficult due to the relatively cathodic standard reduction potentials, multiple valence states, and complex oxy-anion solution phase chemistry. 5 Mo electrodeposition has been reported mainly from non-aqueous electrolytes such as high temperature molten salts. 6-8 More recently, Mo electrodeposition from aqueous electrolytes has also been reported, 9,10 but either without evidence for complete reduction to Mo(0), 9 or with extremely low current efficiency due to copious hydrogen evolution. 10 Mo alloys with a Mo content less than 50% can also be obtained from aqueous electrolytes. [11][12][13] We report galvanic deposition of compact Mo thin films onto Al 6061 alloy from a simple aqueous electrolyte. Energy dispersive X-ray spectroscopy (EDX) measurements indicate that these films contain primarily Mo and Al. These galvanic Mo films are also characterized by voltammetry and electrochemical impedance spectroscopy (EIS) in 0.5 M H 2 SO 4 and in 3.5 wt% NaCl electrolyte at pH 2, 7 and 12. ExperimentalConcentrated HNO 3 was obtained from J.T. Baker, MoCl 5 was obtained from Alfa Aesar, and 99.999% pure Al rod and 6061 Al foil (76 μm thick) were obtained from ESPI Metals. Al 6061 alloy typically contains 0.8-1.2 wt% Mg, 0.4-0.8 wt% Si, ≤ 0.70 wt% Mg, 0.15-0.40 wt% Cu, 0.04-0.35 wt% Cr, and smaller amounts of Mn, Ti, and Zn. Prior to Mo deposition, 6061 Al alloy was roughened with 150 grit Al 2 O 3 sandpaper and rinsed with water according to ASTM standard B253-11. MoCl 5 is corrosive and water-reactive, so it was stored under vacuum, and all experiments were performed in a chemical fume hood. All experiments were performed at room temperature (20 • C).Voltammetry and open circuit potential measurements were performed with an EG&G PAR model 273A potentiostat/galvanostat with an Al 6061 foil working electrode, Pt counter electrode, and SCE reference electrode. Electrochemical impedance spectroscopy (EIS) measurements were performed with a Solartron 1250 frequency respo...

For the first time, galvanic deposition of Ti is reported from aqueous solutions containing 17 mM HF and 10 mM K 2 TiF 6 at pH 2.73 onto Al 6061 alloy. X-ray diffraction yields peaks consistent with a polycrystalline Ti deposit, and electrical resistivity measurements are also consistent with metallic Ti, not TiO 2 . Elemental analysis by energy dispersive X-ray (EDX) spectroscopy demonstrates the as-deposited film contains ∼90 atom% Ti. The galvanic Ti deposit improves the corrosion resistance of the underlying Al substrate, as illustrated by voltammetry and electrochemical impedance spectroscopy studies in several electrolytes. Deposition for 30 h. yields a 14 μm thick, silver-gray Ti film.Ti has numerous applications in the microelectronics, aerospace, and biomedical industries due to its excellent mechanical properties, corrosion resistance and biocompatibility. 1,2 Ti is a refractory metal with a high strength to weight ratio and low modulus of elasticity, and is therefore used in dental implants and prostheses. Ti provides a favorable foreign body response after implantation, which leads to mineralization and titanium osseointegration. 3,4 Thin films of Ti are also employed for their corrosion resistance, 5,6 and as diffusion barrier layers within electronic devices. 7 Ti thin films are typically deposited by evaporation and sputtering methods using expensive vacuum systems. 8-10 Electrochemical deposition is generally simpler and less expensive, but Ti electrodeposition from aqueous electrolytes is difficult due to the highly cathodic potential required. For this reason, Ti electrodeposition is typically performed from high temperature molten salts. 1 We report the room temperature galvanic deposition of Ti thin films onto Al 6061 alloy. X-ray diffraction and electrical resistivity measurement of the galvanic Ti film are consistent with a polycrystalline Ti deposit rather than TiO 2 . Energy dispersive X-ray spectroscopy (EDX) indicates that these films contain 89-91 atom% Ti. The corrosion resistance of Ti atop Al 6061 alloy is studied by voltammetry and electrochemical impedance spectroscopy (EIS). ExperimentalReagent grade chemicals were used for all experiments. Semiconductor grade HF was obtained from J.T Baker, while K 2 TiF 6 was obtained from Sigma Aldrich. 99.999% pure Al and Al 6061 alloy rods were obtained from ESPI Metals. Al 6061 alloy typically contains 0.8-1.2 wt% Mg, 0.4-0.8 wt% Si, ≤0.70 wt% Mg, 0.15-0.40 wt% Cu, 0.04-0.35 wt% Cr, and smaller amounts of Mn, Ti and Zn. The Al rods were cut into stubs of approximately 1.5 cm. The Al electrodes were polished sequentially with 600, 1500, 2400, 4000 grit Al 2 O 3 sand papers, and finally with 50 nm Al 2 O 3 , then rinsed with acetone and twice distilled water.For studies of corrosion resistance in four model electrolytes, electrochemistry was performed in a three-electrode cell with the Ti/Al film working electrode, Pt counter electrode and SCE reference electrode. Voltammetry was performed from −1070 mV to -650 mV vs. SCE with a scan rate of 0...

We report an impedance biosensor utilizing a Si electrode created by wet chemical deposition atop 6061 Al alloy. The sensor electrode is created by galvanic/electroless Si deposition from an electrolyte containing 10 mM HF and 20 mM Na2SiF6 in 80 wt% formic acid, followed by antibody immobilization. The impedance response of the sensor electrode to increasing concentrations of peanut protein Ara h 1, a common food allergen, can be fit to an equivalent circuit containing three RC loops. The circuit element most sensitive to antigen binding is the charge transfer resistance, yielding a detection limit of 4 ng/mL.Biosensors that utilize electrochemical impedance spectroscopy have been employed with a wide variety of immobilized biomolecules, including antibodies, receptor proteins, aptamers, and ssDNA.

Energy storage addresses the problem of sustainability for renewable but intermittent energy sources like solar, wave and wind power. Electrochemical supercapacitors represent a new technology that helps meet the demands for high power and energy density for the optimal storage of renewable but intermittent energy sources. For inclusion in supercapacitors, transition metal oxide and sulfide electrodes such as RuO2, IrO2, TiS2, and MoS2 exhibit rapid faradaic electron–transfer reactions combined with low resistance. The pseudocapacitance of RuO2 is about 720 F/g and is 100 times greater than the double-layer capacitance of activated carbon electrodes. However syntheses of these oxide and sulfide electrode materials can be expensive and are not presently in commercial use. We report cathodic electrodeposition of molybdenum disulfide onto glassy carbon electrodes from electrolytes containing 10 mM (NH4)2MoS4 and 0.2 M KCl. Four minutes of electrodeposition yields compact 1 µm thick MoS2 film deposit, as confirmed by SEM/EDX analysis, whereas longer deposition times yields much thicker MoS2 film but with nanoscale cracks. The film capacitance is studied as a function of bulk film thickness and crystallinity. X-ray diffraction analysis demonstrates crystallization of MoS2 after annealing in Ar at 600°C for 1 hr. The electrochemical performance of both amorphous and crystalline MoS2 films is studied in 1 M TEA-BF4 in acetonitrile by electrochemical impedance spectroscopy, cyclic voltammetry and chronocoulometry. The films demonstrate stable pseudocapacitive behavior; for both the amorphous and annealed films, with specific capacitances of 40 F/g and 300 F/g, respectively. Studies as a function of MoS2 thickness demonstrate that the capacitance eventually plateaus’, suggesting that only the near-surface region is available for charge storage. Results will also be presented for electrochemical impedance spectroscopy and atomic force microscopy of these films before and after capacitance cycling.