Electrodeposition of Protocrystalline Germanium from Supercritical Difluoromethane

Electrochemical Approaches for the Recovery of Metals from Electronic Waste: A Critical Review

Electronic waste (e-waste) management and recycling are gaining significant attention due to the presence of precious, critical, or strategic metals combined with the associated environmental burden of recovering metals from natural mines. Metal recovery from e-waste is being prioritized in metallurgical extraction owing to the fast depletion of natural mineral ores and the limited geographical availability of critical and/or strategic metals. Following collection, sorting, and physical pre-treatment of e-waste, electrochemical processes-based metal recovery involves leaching metals in an ionic form in a suitable electrolyte. Electrochemical metal recovery from e-waste uses much less solvent (minimal reagent) and shows convenient and precise control, reduced energy consumption, and low environmental impact. This critical review article covers recent progress in such electrochemical metal recovery from e-waste, emphasizing the comparative significance of electrochemical methods over other methods in the context of an industrial perspective.

Fast and safe synthesis of micron germanium in an ammonia atmosphere using Mo2N as catalyst

Here, we reported a new method for fast and safe synthesis of a micron germanium (Ge) semiconductor. The Ge was successfully prepared from mixed GeO₂ with a low amount of MoO₃ by the NH₃ reduction method at 800 °C for an ultra-short time of 10 min. XRD patterns show that the Ge has a tetragonal structure. SEM images show that the size of the Ge particles is from 5 μm to 10 μm, and so it is on the micron scale. UV-visible diffuse reflectance spectroscopy shows that the Ge has good light absorption both in the ultraviolet and visible regions. The formation of Ge mainly goes through a two-step conversion in the NH₃ flow. Firstly, GeO₂ is converted to Ge₃N₄, and then Ge₃N₄ is decomposed to generate Ge. The comparison experiments of MoO₃ and Mo₂N demonstrate that Mo₂N is the catalyst for the Ge synthesis which improves the Ge₃N₄ decomposition. The presented fast and safe synthesis method of Ge has great potential for industrialization and the proposed Mo₂N boosting the Ge₃N₄ decomposition has provided significant guidance for other nitride decomposition systems.

Here, we reported a new method for fast and safe synthesis of a micron germanium (Ge) semiconductor.

Electrochemical Scanning Tunneling Microscopic Study of the Potential Dependence of Germanene Growth on Au(111) at pH 9.0

Germanene is a 2D material whose structure and properties are of great interest for integration with Si technology. Preparation of germanene experimentally remains a challenge because, unlike graphene, bulk germanene does not exist. Thus, germanene cannot be directly exfoliated and is mostly grown in ultrahigh vacuum. The present report uses electrodeposition in an aqueous HGeO₃^- solution at pH 9. Germanene deposition has been limited to 2-3 monolayers, thus greatly restricting many applicable characterization methods. The in situ technique of electrochemical scanning tunneling microscopy was used to follow Ge deposition on Au(111) as a function of potential. Previous work by this group at pH 4.5 suggested germanene growth, but no buffer was used, resulting in change in surface pH. The addition of borate buffer to create pH 9.0 solution has reduced hydrogen formation and stabilized the surface pH, allowing systematic characterization of germanene growth versus potential. Initial germanene nucleated at defects in the Au(111) herringbone (HB) reconstruction. Subsequent growth proceeded down the face-centered cubic troughs, slowly relaxing the HB. The resulting honeycomb (HC) structure displayed an average lattice constant of 0.41 ± 0.06 nm. Continued growth resulted in the addition of a second layer on top, formed initially by nucleating around small islands and subsequent lateral 2D growth. Near atomic resolution of the germanene layers displayed small coherent domains, 2-3 nm, of the HC structure composed of six-membered rings. Domain walls were based on defective, five- and seven-membered rings, which resulted in small rotations between adjacent HC domains.

Imidazolium-based ionic liquids with large weakly coordinating anions

An investigation into the intramolecular interactions in a series of imidazolium salts with weakly coordinating anions reveals that it is possible to control the strength and location of hydrogen bonding by varying the substituents on the imidazolium cation.