Solution-Processed Synthesis of Copper Oxide (Cu_xO) Thin Films for Efficient Photocatalytic Solar Water Splitting

Abstract

This article reports a solution-processed synthesis of copper oxide (Cu x O) to be used as a potential photocathode for solar hydrogen production in the solar water-splitting system. Cu x O thin films were synthesized through the reduction of copper iodide (CuI) thin films by sodium hydroxide (NaOH), which were deposited by the spin coating method from CuI solution in a polar aprotic solvent (acetonitrile). The phase and crystalline quality of the synthesized Cu x O thin films prepared at various annealing temperatures were investigated using various techniques. The X-ray diffraction and energy dispersive X-ray spectroscopy studies confirm the presence of Cu 2 O, CuO/Cu 2 O mixed phase, and pure CuO phase at annealing temperatures of 250, 300, and 350 °C, respectively. It is revealed from the experimental findings that the synthesized Cu x O thin films with an annealing temperature of 350 °C possess the highest crystallinity, smooth surface morphology, and higher carrier density. The highest photocurrent density of −19.12 mA/cm 2 at −1 V versus RHE was achieved in the photoelectrochemical solar hydrogen production system with the use of the Cu x O photocathode annealed at a temperature of 350 °C. Therefore, it can be concluded that Cu x O synthesized by the spin coating method through the acetonitrile solvent route can be used as an efficient photocathode in the solar water-splitting system.

Photoelectrochemical Hydrogen Production by Screen-Printed Copper Oxide Electrodes

“…Table 3 shows comparable bandgap values for Cu2O and Cu2O/CuO-based films, respectively. The obtained results are in good agreement with the ones reported in literature [23,32]. For the Cu2O/CuO-based layers, the bandgap values decrease compared with the layers of Cu2O, due to the combination of the different copper phases produced by the different thermal treatments that finally extends the light adsorption range.…”

Copper Oxide-Based Photocatalysts and Photocathodes: Fundamentals and Recent Advances

“…In particular, CuO has been often proposed as an overlayer for Cu 2 O to promote electron transport towards the electrolyte, thus reducing the probability of charge recombination and increasing the lifetime. When used as a photocathode, this combination lead to impressive photocurrents up to −19.12 mA cm −2 at −1 V versus RHE [ 17 ]. Cu 2 O/CuO systems have an extended absorption spectra compared to pure Cu 2 O: While the latter have an absorption edge at about 600 nm, the former have a stronger absorption in the visible region—up to near-infrared (NIR), whose edge is at about 900 nm, due to the low band gap energy of CuO [ 18 ].…”

Effect of substrate temperature on the optoelectronic properties of DC magnetron sputtered copper oxide films

“…Copper oxide is a p-type nontoxic metal oxide semiconductor, possessing a wide range of applications in gas sensors, as hole transport layers in solar cells, and also in electrochromic devices [1,2]. There are normally two oxides of copper: cuprous or copper (I) oxide (Cu 2 O), with a direct band gap slightly above 2.0 eV and cupric or copper (II) oxide (CuO) having an indirect band gap between 1.3-2 eV [3][4][5][6]. A metastable, intermediate copper oxide compound between the above mentioned two phases, Cu 4 O 3 , having catalytic properties has also been reported [7,8].…”