Enhanced photoelectrochemical water splitting performance of CuBi2O4 nanosphere photocathode by CuO decoration

Abstract

A photoelectrochemical cell (PEC) was invented a few decades ago to split water molecules into hydrogen (H₂) and oxygen (O₂) gases. Historically, the efficiency of PEC has been relatively small, which limits its application in the field of H₂ fuel generation. In this work, CuBi₂O₄ and enchanted CuO/CuBi₂O₄ heterostructures were investigated. The pure and enchanted nanostructures were synthesized by a one-pot hydrothermal method. The film coated on the transparent conducting electrode employed the doctor blade method. The crystal structures of the products were analyzed by X-ray diffraction. The crystal structure of CuBi₂O₄ and CuO were identified as kusachiite and ternorite, respectively. Scanning electron microscopy, Transmission electron microscopy, and X-ray photoelectron spectroscopy investigated those materials' surface morphology and chemical species. The photocurrent density of the material was investigated under visible light illumination. The photocurrent signal of all CuO/CuBi₂O₄ heterostructure photocathodes exhibited higher values than the pristine CuBi₂O₄ and CuO. The photocurrent of the best CuO/CuBi₂O₄ heterostructure photocathode was 1.2 mA/cm⁻² at applied 0.5 V (vs. RHE) greater than 5 times the pure CuBi₂O₄ and CuO materials. Electrochemical impedance spectroscopy was used to reveal the internal impedance of the PEC. Regarding the CuO forming to CuBi₂O₄, the internal resistance of all CuO/CuBi₂O₄ photocathodes showed lower impedance, and the Mott-Schottky analysis showed that the charge carrier density of CuBi₂O₄ enhanced by CuO was increased, resulting in a greater photocurrent density of the PEC.