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Electrochemical deposition of rhenium-ruthenium (Re-Ru) was investigated to probe the impacts of adsorbed hydrogen on the co-deposition of binary alloy. Cyclic voltammetry, chronoamperometry, and X-ray fluorescence were utilized to characterize the electrochemical system and to determine the deposition partial current densities of each element. A thickness dependent deposition rate of rhenium was observed and was further studied in conjunction with the hydrogen evolution reaction on different substrates. The results are discussed in a framework of multi-step reduction mechanism involving the adsorbed hydrogen intermediate species. While the co-deposition of Ru with Re modifies the Cu electrode surface, promoting the Re deposition rate at the initial stage, the subsequent deposition on the alloy itself reveals a mutual inhibitive interaction between the two. Preliminary studies on Re co-deposition with Cd and Zn further confirm the effect of adsorbed hydrogen intermediate, where the much weaker affinity on these metals nearly disables the Re deposition. 

ReMo binary alloy films with a maximum Mo content of 25 at. % are successfully electrodeposited using high concentration acetate solutions in the presence of citric acid. The electrochemical behavior of the ReMo alloy is studied using cyclic voltammetry and anodic stripping methods. Different techniques, including electron microscopy, x-ray diffraction, and four-point probe resistance measurements at cryogenic temperature, are used to characterize the surface morphology, crystal structure, and superconducting critical temperature of alloys, respectively. While all films exhibit a crystalline hcp phase after 700 °C annealing, the film with the highest 25 at. % Mo content shows a second crystalline cubic phase. Mo doping preserves the enhanced superconducting transition temperature (Tc) in electrodeposited amorphous Re films and improves the stability of Tc against thermal annealing at a temperature of 200 °C. This is the first successful demonstration to use a dopant to stabilize the enhanced Tc of electrodeposited films, enabling the fabrication and operation of superconducting connectors above the intrinsic Tc of the materials. 

This paper reports a systematic study on the electrodeposition of metallic molybdenum from water-in-salt electrolytes containing superhigh concentrations of acetate. Cyclic voltammetry and DC deposition were carried out on rotating disk electrodes with various concentrations of CH₃COOK and CH₃COONH₄to determine the effects of NH₄⁺and K⁺on Mo deposition. A comparison was performed between CH₃COOLi, CH₃COONa, and CH₃COOK to study the effects of different alkali metal cations. A synergistic effect was observed between K⁺and NH₄⁺, where Mo deposition rate is enhanced in the presence of both cations. However, such synergistic effect was not observed between NH₄⁺and other alkali cations. In addition, the impact of substrate on Mo deposition was also studied using Pt and Cu electrodes with different activity toward hydrogen evolution reaction. Electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the surface morphology, crystallographic structure, and metallic state of Mo in the electrodeposited films.