Fabricating highly efficient heterostructured CuBi2O4 photocathodes for unbiased water splitting

Abstract

Developing photocathodes with a high photocurrent density and large onset potential is crucial for achieving solar driven water splitting. Herein, we report an efficient copper bismuth oxide (CuBi₂O₄) photocathode with a unique two-dimensional (2D) porous heterojunction structure. By designing a type II heterojunction structure with CuO, the resultant CuBi₂O₄/CuO photocathode exhibits a photocurrent density of 1.49 mA cm⁻² at 0.6 V_SHE, which is over 2 times that of the pristine CuBi₂O₄ photocathode. Further anodization treatment leads to an improved photocurrent density of 1.87 mA cm⁻² at 0.6 V_SHE, which is the highest photoresponse for CuBi₂O₄-based photocathodes. The synergistic effect of high surface area, short charge transfer distance in the 2D structure, efficient charge transfer and improved conductivity are the key reasons for the good performance of the CuBi₂O₄/CuO photocathodes. Moreover, the onset potential of the anodized CuBi₂O₄/CuO photocathode was over 1.1 V_SHE, enabling an unbiased photoelectrochemical water splitting process by combining with a BiVO₄ photoanode. This work highlights the good potential of CuBi₂O₄ in achieving a spontaneous overall water splitting process.