Optimization of processing parameters for the preparation of dip-coated CuO photocathodes and modification with Au nanoparticles for water-splitting

Abstract

Here, the processing parameters for preparing dip-coated CuO photocathodes such as withdrawal velocity, film thickness, and calcination temperature were optimized for photoelectrochemical (PEC) applications. CuO films were prepared at varying withdrawal rates between 50 and 200 mm/min, made to consist of 239.7–693.6 ± 40 nm film thicknesses, and annealed at 400–650 °C for 1 h. Furthermore, Au nanoparticles (Au NPs) were deposited on the CuO films that were prepared at 150 mm/min withdrawal velocity, 432.8 ± 27 nm thick, and treated at 600 °C to protect the films against photo-corrosion during PEC reactions. The prepared films were confirmed to be of high purity via Raman spectroscopy and X-ray diffraction (XRD) studies. The maximum photocurrent density of 2.9 mA/cm2 at 0.35 V vs RHE was obtained for the CuO photocathodes prepared at 150 mm/min withdrawal velocity, with the thickness of 432.8 nm, and treated at 600 °C. The high photocurrent density has been linked to the combine effect of the optimization of film thickness, optical absorbance, crystallization, and the low resistance to charge transfer at the photocathode/electrolyte junction exhibited by the films. The deposition of Au NPs on the pristine CuO photocathodes resulted in a 62% drop in their photocurrent density due to the inhibition of high photo-corrosion occurring on the film's surface. A potential-time scan at 0.6 V vs RHE for 500 s yielded a 3-fold improvement in the photo-stability of the Au coated films in electrolyte over the pristine CuO photocathodes. This study emphasized the role of optimizing multiple processing parameters in the fabrication of CuO photocathodes before the deposition of protective layers for water splitting applications.