Photoelectrochemical Characterization of Spin-Coated CuBi2O4 Thin Films for Water Splitting

Complex oxides containing multiple cations or in some cases multivalent cations such as Bi^3+,5+, Co^2+,3+, Sn^2+,4+, have attracted much attention for photoelectrochemical applications due to their unique properties. Bismuth has a multivalent nature (Bi³⁺, Bi⁵⁺) that can be present at the same time in the same crystal structure in the Bi site, improving the conductivity of the material. An interesting new p-type semiconductor, which has shown high photocurrent under visible light conditions, is CuBi₂O₄ [1]. In this work, we present the growth of CuBi₂O₄ thin films prepared by spin coating method on FTO glass substrate. The precursor solution was prepared using bismuth nitrate, copper nitrate and dilute aqueous acetic acid as a solvent. The films were spin coated and annealed at 650°C.

The influence of parameters such as the heating rate during sintering and the substrate’s etching treatment on the films quality was studied. The films were characterized by X-ray diffraction, SEM, and UV-Vis spectrophotometry. We observed that the heating rate is an essential parameter to obtain a homogeneous layer. The optical response and photoelectrochemical behavior were studied as function of the film thickness. We show that the material is capable of reducing water under sunlight.

[1] L. Wei, C. Shifu, Z. Sujuan, Z. Wei, Z. Huaye, Y. Xiaoling, Journal of Nanoparticle Research 2010, 12, 1355-1366.