Electrochemical investigation of electrodeposited Fe–Pd alloy thin films

Microstructure and Magnetic Properties of Fe67.6-Pd32-In0.4 (at.%) Shape Memory Melt-Spun Ribbons

Fe-~30 at.%Pd is a ferromagnetic shape memory alloy (SMA) with a reversible thermoelastic fcc-fct phase transformation. The advantage of adding a small amount of Indium to Fe-Pd SMAs is, among other things, the upward shift of the transformation temperatures, which allows us to maintain the material in the martensitic state (fct structure) at room temperature. In this work, we study the microstructure and the magnetic properties of nominally Fe67.6-Pd32-In0.4 (at.%) melt-spun ribbons. Energy-dispersive spectroscopy analysis showed a certain level of non-uniformity of Indium distribution in the as-spun ribbon. However, the attempt to homogenize the ribbon by annealing at 1273 K for 120 h resulted in an unfavoured structural change to bct martensite. Magneto strains induced by a 9 kOe magnetic field reached over 400 ppm for certain field orientations, which is around four times more than the magneto strains of near-binary Fe-Pd shape memory alloys.

The Electrochemical Reduction Mechanism of ZnFe2O4 in NaCl-CaCl2 Melts

The electrochemical reduction process of ZnFe2O4 in NaCl-CaCl2 melts was studied. Thermodynamic analysis shows that the reduction process of ZnFe2O4 is carried out in multiple steps, and it is difficult to reduce Fe3+ to Fe in one step. Electrochemical tests revealed that the reduction process of ZnFe2O4 includes three steps: First, Fe3+ is reduced to Fe in two steps, then Zn2+ is reduced to Zn in one step. The reduction of Fe3+ on the Mo electrode is a reversible process controlled by diffusion, while the reduction of Zn2+ is an irreversible process controlled by diffusion. The influence of electrolysis voltage and temperature on the process of electric deoxidation has also been studied. It is indicated that properly increasing the temperature is conducive to the diffusion of oxygen ions, thereby increasing the deoxidation rate. With the gradual increase of voltage, the reduction process of ZnFe2O4 is ZnFe2O4 → FeO + ZnO → Fe + ZnO → Fe + Zn.

Electrochemical recovery of Ni metallic in molten salts from spent lithium-ion battery

Massive deployment of lithium-ion battery inevitably causes a large amount of solid waste. To be sustainably implemented, technologies capable of reducing environmental impacts and recovering resources from spent lithium-ion battery have been an urgent task. The electrochemical reduction of LiNiO2 to metallic nickel has been reported, which is a typical cathode material of lithium-ion battery. In this paper, the electrochemical reduction behavior of LiNiO2 is studied at 750 °C in the eutectic NaCl-CaCl2 molten salt, and the constant cell voltage electrolysis of LiNiO2 is carried out. The results show that Ni(III) is reduced to metallic nickel by a two-step process, Ni(III) → Ni(II) → Ni, which is quasi-reversible controlled by diffusion and electron transfer. After electrolysis for 6 h at 1.4 V, the surface of LiNiO2 cathode is reduced to metallic nickel, with NiO and a small amount of Li0.4Ni1.6O2 detected inside the partially reduced cathode. After prolonging the electrolysis time to 12 h, LiNiO2 is fully electroreduced to metallic nickel, achieving a high current efficiency of 98.60%. The present work highlights that molten salt electrolysis could be an effective protocol for reclamation of spent lithium-ion battery.

A comparative study of the influence of the deposition technique (electrodeposition versus sputtering) on the properties of nanostructured Fe70Pd30 films

Sputtering and electrodeposition are among the most widespread techniques for metallic thin film deposition. Since these techniques operate under different principles, the resulting films typically show different microstructures even when the chemical composition is kept fixed. In this work, films of Fe₇₀Pd₃₀ were produced in a thickness range between 30 and 600 nm, using both electrodeposition and sputtering. The electrodeposited films were deposited under potentiostatic regime from an ammonia sulfosalicylic acid-based aqueous solution. Meanwhile, the sputtered films were deposited from a composite target in radio frequency regime. Both approaches were proven to yield high quality and homogenous films. However, their crystallographic structure was different. Although all films were polycrystalline and Fe and Pd formed a solid solution with a body-centered cubic structure, a palladium hydride phase was additionally detected in the electrodeposited films. The occurrence of this phase induced internal stress in the films, thereby influencing their magnetic properties. In particular, the thickest electrodeposited Fe₇₀Pd₃₀ films showed out-of-plane magnetic anisotropy, whereas the magnetization easy axis lied in the film plane for all the sputtered films. The domain pattern of the electrodeposited films was investigated by magnetic force microscopy. Finally, nanoindentation studies highlighted the high quality of both the sputtered and electrodeposited films, the former exhibiting higher reduced Young's modulus and Berkovich hardness values.

Galvanic replacement of electrodeposited nickel by palladium and investigation of the electrocatalytic activity of synthesized Pd/(Ni) for hydrogen evolution and formic acid oxidation

Highly active Pd/(Ni) catalysts were synthesized by well controlled galvanic replacement of electrodeposited nickel, towards hydrogen evolution and FA oxidation.

Controlled electrodeposition of nanostructured Pd thin films from protic ionic liquids for electrocatalytic oxygen reduction reactions

Nanostructured Pd thin films are prepared from protic ionic liquids via hydrogen-assisted electrodeposition for oxygen reduction reactions.