From $Cu2(OH)3Cl$ to nanostructured sisal-like $Cu(OH)2$ and CuO: Synthesis and characterization

$Cu2(OH)3Cl$ with an average size of $5–10μm$ have been synthesized by a simple hydrothermal reaction with a yield of $∼100%$⁠. After the as-prepared $Cu2(OH)3Cl$ was treated with NaOH solution, the green crystals were converted to blue sisal-like $Cu(OH)2$ with needle-like nanorods pointing out radially from the core. These nanorods were about 100–200 nm in diameter and $10μm$ in length. Using the sisal-like $Cu(OH)2$ as sacrificial precursor, CuO with a well-preserved morphological feature of the precursor was formed through thermal treatment. The samples were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, BET nitrogen adsorption, and UV-visible absorption spectroscopy. The conversion of the synthesized $Cu2(OH)3Cl$ to sisal-like $Cu(OH)2$ was optically visualized and confirmed by corresponding SEM images, and an “etching-and-growing” mechanism was proposed. The results also show that the as-prepared CuO possesses a band gap of 2.27 eV and high specific surface area $(75.8m2/g)$⁠, and its surface is highly rich in O.