The CuBi2O4/NiO Heterojunction Thin Films for Highly Efficient Solar Water Splitting

Abstract

Despite the advantages of the CuBi2O4 (CBO) photocathode with the exceptionally positive onset-potential for water reduction, the photocatalytic limitations of the CBO photocathode, including poor charge transport properties and bad chemical stability, have been the principal obstacles to the utilization of the CBO as a photocathode for solar water splitting. To overcome these limitations of the CBO photocathode, we have fabricated the highly polycrystalline CBO photocathode in coupling with the intermediate layer, NiO, using a pulsed laser deposition (PLD) to form type-II band alignment which is well known to enhance the charge transport efficiency. As a result, the photocurrent density of the CBO/NiO type-II heterojunction photocathode exhibits 1.5 times higher than that of the bare CBO photocathode at 0.4 VRHE due to the significant improvement of charge transport property. Furthermore, the long-term chemical stability was also achieved on both bare CBO and CBO/NiO type-II heterojunction thin film without any other protection layer owing to the growth of high-crystalline films via PLD. These results strongly suggest that the growth of the type-II heterojunction thin films by using PLD is the most effective way to improve the photoactivity properties of the CBO photocathode with the long-term chemical stability for solar water splitting