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We report a gradual transition in the deposition product from pure Cu2O to pure Cu, during electrodeposition on Au/Pd sputter-coated silicon wafer substrates in copper sulphate electrolyte with various dc potential. At voltages lower than 0.3V, only pure Cu in a nanocrystalline form is deposited on the cathode substrate, while at voltages higher than 1.2V, only pure Cu2O, also in a nano/microcrystalline form, is deposited. At intermediate voltages between 0.3 to 1.2 V, the deposition product comprises a mixture of both Cu and Cu2O nano/micro-crystals. The Cu2O crystals are generally of an octahedral shape with sizes ranging from 30nm to 100nm, while Cu nano/microcrystals are of irregular shape ranging from 100nm to 2μm. This work provides a method to fabricate nanocrystalline Cu2O, Cu and Cu/Cu2O on substrates in a single step without the use of additives.

One-and two-dimensional cuprous oxide (Cu 2 O) nanostructures were fabricated on highly orientated pyrolytic graphite (HOPG) by electrodeposition in CuSO 4 at room temperature (25 o C) with no additives. For short deposition times, 1D Cu 2 O single nanocrystals were generally of an octahedral shape with sizes ranging from 50nm to 400nm, while 2D Cu 2 O nanowires with diameters ranging from 100nm to 300nm had lengths of more than 100μm. With longer deposition times, microwires were found to have diameters ranging from 1μm to 2μm with lengths up to 60μm, while microcrystals were also produced with sizes 1μm to 6μm. The highly aligned Cu 2 O nano/microwires were found to be deposited on the step edges of the HOPG substrate. Various crystal morphologies including flower-like and butterfly-like structures, and dendrites and truncated octahedra were observed on the working electrode of HOPG. Some of the morphologies are revealed for the first time by one step electrodeposition and these are confirmed to be single Cu 2 O crystals.

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