Fabrication and Characterization of P-Type Semiconducting Copper Oxide-Based Thin-Film Photoelectrodes for Solar Water Splitting

Abstract

Solar light-driven hydrogen by photocatalytic water splitting over a semiconductor photoelectrode has been considered a promising green energy carrier. P-type semiconducting copper oxides (Cu2O and CuO) have attracted remarkable attention as an efficient photocathode for photoelectrochemical (PEC) water splitting because of their high solar absorptivity and optical band gaps. In this study, CuO thin films were prepared using the sol-gel spin coating method to investigate the effects of aging time and layer dependency. Electrodeposition was also applied to fabricate Cu2O thin films. Cu2O thin films annealed at 300 °C are a hetero-phase system composed of Cu2O and CuO, while those at 400 °C are fully oxidized to CuO. Thin films are characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-VIS), Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry (SE), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman microscopy. The hetero-phase thin films increase the photoconversion efficiency compared to Cu2O. Fully oxidized thin films annealed at 400 °C exhibit a higher efficiency than the hetero-phase thin film. We also verified that CuO thin films fabricated using electrodeposition show slightly higher efficiency than the spin coating method. The highest photocurrent of 1.1 mA/cm2 at 0.10 V versus RHE was measured for the fully oxidized CuO thin film under one-sun AM1.5G illumination. This study demonstrates a practical method to fabricate durable thin films with efficient optical and photocatalytic properties.

Electrodeposition of Copper Oxides as Cost-Effective Heterojunction Photoelectrode Materials for Solar Water Splitting

“…It was found that the root mean square (RMS) roughness of the thin films increased from 21.6 nm (Cu 2 O) to 33.9 nm (CuO/Cu 2 O at 350 • C) and 46.5 nm (CuO at 500 • C) (Cu 2 O < CuO/Cu 2 O < CuO). We assume that the controlling of thin film thicknesses using the electrolyte temperature affects RMS roughness [40]. Furthermore, since the light absorption properties of thin films play an essential role in PEC performance, we measured the absorbance of Cu 2 O, CuO/Cu 2 O, and CuO thin films using a UV-Vis spectrometer.…”

“…It is also known that they are a potential electrode material for photovoltaic applications [24] because of their cost-effectiveness, non-toxicity, excellent carrier mobility [25], and high absorption coefficient. Similarly, these advantages make copper oxides suitable as an efficient photoelectrode for PEC water splitting, as shown in Table S1 [26][27][28][29][30][31][32][33][34][35][36][37] and Table S2 [38][39][40]. One crucial obstacle to copper oxides may be their high electron-hole recombination rate, lowering photoconversion efficiencies.…”

“…In this work, we reported a facile method to prepare a CuO/Cu 2 O heterojunction structure for PEC water splitting. Cu 2 O thin films were prepared by electrodeposition, and thermal treatment was performed [28,40,48]. Simple and eco-friendly electrodeposition by controlling annealing temperatures resulted in micron thick copper oxide layers (~1.4 µm thick) compared to physical methods (i.e., sputtering and pulsed laser deposition).…”

A Cost-Effective, Nanoporous, High-Entropy Oxide Electrode for Electrocatalytic Water Splitting

“…Although green hydrogen production from renewable energy sources is considered a promising approach for net-zero carbon emissions [6,7], ~95% of global hydrogen production is based on fossil fuels [8] (i.e., gray or brown hydrogen), releasing carbon emissions [9]. Hence, developing high-efficiency green hydrogen production technologies from water (i.e., electrochemical [10] and photoelectrochemical (PEC) water electrolysis [11,12]) is imperative. In particular, developing novel high-performance electrode materials for the oxygen evolution reaction (OER) for electrochemical and PEC water electrolysis has attracted much attention because its sluggish reaction kinetics retard large-scale hydrogen production [13].…”

Electrodeposition of Zn Zn-doped Cu Cu2O in Acidic and Alkaline Solution and Its Catalytic Activity for Ethanol Electrooxidation

“…However, despite these promising advantages, the doping of Zn cation in the electrodeposited Cu2O thin film, which has low bandgap energy and good photocatalytic activity, has not been experimentally proven, particularly regarding its electrocatalyst activity for ethanol electrooxidation applications. The aim of the present study was to synthesize Zn-doped Cu2O thin films by an electrodeposition, which is known as versatile method to fabricate metal [15]- [17] and metal oxide film, on indium tin oxide (ITO) substrate. The structure,…”