Abstract:
Copper (II) oxide (CuO) nanostructures were
prepared on fluorine-doped tin oxide (FTO) using a three-step
heat treatment process in a sol−gel dip-coating method. The
precursor used for the dip-coating process was prepared using copper
acetate, propan-2-ol, diethanolamine, and polyethylene glycol 400.
Dip-coated films in layers of 2, 4, 6, 8, and 10 were prepared by drying
each layer at 110 and 250 °C for 10 and 5 min, respectively, followed
by calcination at 550 °C for 1 h. The films were applied toward
photocatalytic hydrogen evolution from water. The X-ray diffraction
(XRD) pattern of the films confirmed the tenorite phase of pure
CuO. Raman spectroscopy revealed the 1Ag and 2Bg phonon modes
of CuO, confirming the high purity of the films produced. The CuO
films absorb significant photons in the visible spectrum due to their
low optical band gap of 1.25−1.33 eV. The highest photocurrent of −2.0 mA/cm2 at 0.45 V vs reversible hydrogen electrode (RHE)
was recorded for CuO films consisting of six layers under 1 sun illumination. A more porous surface, low charge transfer resistance,
and high double-layer capacitance at the CuO/electrolyte interface observed for the films consisting of six layers contributed to the
high photocurrent density attained by the films. CuO films consisting of six layers prepared using the conventional two-step heat
treatment process for comparative purposes yielded 65.0% less photocurrent at 0.45 V vs RHE compared to similar films fabricated
via the three-step heating method. The photocurrent response of the CuO nanostructures prepared using the three-step heat
treatment process is promising and can be employed for making CuO for photovoltaic and optoelectronic applications.
