Tuning of the structural, morphological, optoelectronic and interfacial properties of electrodeposited Cu2O towards solar water-splitting by varying the deposition pH

Abstract

In the present work investigations on the morphological, structural, optoelectronic, and photoelectrochemical properties of Cu 2 O were carried out in detail at various deposition pH values. It was observed that Cu 2 O maintained the polycrystalline nature and exhibited (111) plane dominance irrespective of the deposition pH. Using the Debye-Scherrer equation and the Williamson-Hall method, the crystallite size and intrinsic lattice strain were observed to decrease with increase in the deposition pH. The crystal shapes were noticed to transform from three-sided pyramids to three-faced prisms and eventually to four-faced pyramids with the increase in bath pH from 5 to 10. Films deposited at lower pH were thicker and showed higher light absorption, and the bandgaps were tunable from 2.03 eV to 2.19 eV. The type of electronic conductivity was tuned from n-type to p-type at the pH of 7, and the flatband potential showed variation from −0.16 V to 0.27 V as the deposition pH was increased. The cathodic photocurrent-density increased as the deposition pH increased from pH 7 to 8 and then decreased after the pH of 8 due to a possible competition between the charge-recombination and charge-migration. • Bath pH has a significant influence on the film thickness of electrodeposited Cu 2 O. • Crystal sizes and lattice strains decrease with increase in the deposition pH. • A red-shift in the light absorption takes place towards the thicker Cu 2 O films. • Bandgaps and the flatband potentials decrease with the decrease in the bath pH. • The overall photocatalytic properties of Cu 2 O can be optimized by varying bath pH.