Study On Preparation And Photoelectrochemical Performance Of Nanostructured Copper Oxides Films

Copper oxide compound semiconductors are abundance in resources, low cost for production, no-toxicity and with narrow band gaps.which makes them have high absorption coefficient in solar spectrum. Cuprous oxide(Cu2O) is one of the direct band gap metal oxide-based semiconductors, band gap is about 2.0 eV. Cupric oxide(CuO) is another important copper-based oxide, band gap is approximately 1.2 eV. They have attracted interest as a good candidate material for photocatalysis, solar cells, photoelectrochemical cell(PEC) because of their high absorption of the visible light. Nanostructured metallic oxides have been widely used in gas sensors, lithium-ion batteries, solar cell and catalyst fields due to their large surface areas and superior physical and chemical properties.In this work, flower-like Cu films were electrodeposited on the substrates of FTO transparent conductive glass. Nanostruture Cu2O and CuO films were obtained through oxidating in air. The thin SnO2 modified porous Cu2O films were prepared by dip-coating of SnO2 sol on the surface of Cu films, followed by annealing in air. The structures, compositions, morphologies and optical properties of samples were characterized by X-ray diffraction(XRD), Raman spectra(Raman), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy(SEM) and UV-Vis diffuse reflection spectroscopy(UV-Vis DRS) respectively. The photoelectrochemical properties of films were analyzed by photocurrent response spectrum. The details are listed below:1.Flower-like Cu films were produced using multi-current steps plating with the first pulse at a current density of 25 mA-cm-2 for 10 s followed by 7.5 mA-cm-2 for 90 s in a solution of 0.05 mol-L-1 Cu(NO3)2+1.5 mol·L-1 lactic. The nanoislands Cu2O films were obtained by heating Cu films at 175℃ for 2 h in air. The results reveal that Cu2O films exhibit favorable photocurrent performance and stability in photoelectrochemical cell. The sample generated -0.25 μA·cm－2 of photocurrent in 0.2 mol·L-1 Na2SO4 at zero bias, under visible light illumination.2. SnO2 modified Cu2O (Cu2O/SnO2) films were prepared by dip-coating SnO2 sol on Cu films, then by annealing at 175℃ for 2 h in air. The results of XRD、 Raman、XPS and SEM showed that thin SnO2 were coated on the surface of porous Cu2O films. It is found that the obtained Cu2O/SnO2 films exhibit superior photocurrent performance and stability over Cu2O in photoelctrochemical cell, the photocurrent of best modified condition is three times higher than pure Cu2O.3. Nanostructured CuO films were synthesized using thermal treatment Cu films under air at 300℃ for 2 h in the furnace. The results reveal that the CuO films showed a stable photocurrent of-3.2 μA·cm-2 in 0.2 mol·L-1 Na2SO4 electrolyte under visible light. The SnO2 modified porous CuO films produced less photocurrent response, however, showed higher stabilities than CuO films.