Shelled germanium nanowires up to 100 nm in diameter and several micrometers in length were prepared by low pressure chemical vapor deposition (LPCVD) of tris(trimethylsilyl)germane (SiMe(3))(3)GeH. Vapors of the precursor were deposited on tantalum substrates in an oven at 365 degrees C. Subsequently, the products were annealed at 700 degrees C in vacuum. The wires consist of a crystalline Ge core surrounded by a two-layer jacket. The presence of hexagonal Ge in the core was documented in some of the nanowires. The inner jacket is formed by amorphous germanium, the outer part by an Si/C material. By annealing at 900 degrees C, germanium in the core is expelled and nanotubes formed by the Si/C material remain. The samples were studied by SEM, HRTEM, EDX, FTIR and Raman spectroscopy, and the XRD technique.

A copper-based catalyst Cu_xSi (3 < x < 5) was prepared using chemical vapor deposition (CVD) of butylsilane (BuSiH₃) on copper substrates. By varying the precursor flow, we obtained two catalyst variants, one with and one without a SiC_x shell. Both variants exhibited large specific areas, owing to the presence of grown nanostructures such as nanoplatelets, nanowires, nanoribbons, and microwires. Remarkably, the catalytic performance of both variants remained stable even after 720 hours of continuous operation. The porous and thick catalyst layer (over a hundred micrometers) on the substrate significantly increased the residence time of intermediates during the electrochemical CO₂ reduction reactions (eCO₂RR). We observed a high selectivity towards ethanol (∼79%) in neutral CO₂-saturated electrolytes and a high selectivity towards acetic acid (∼72%) in alkaline electrolytes. Importantly, the ratio between generated ethanol and acetate could be shifted by adjusting the pH and applied potential. This work thus establishes copper silicides as robust and promising electrocatalysts for selective CO₂ conversion to high-value multi-carbon products.