Co‐optimization of CuBi <sub>2</sub> O <sub>4</sub> photocathode by heterojunction and hole‐selective layer for efficient photoelectrochemical water splitting
Anzheng Zhu, Hai Shan, Simin Cai, Can‐Can Chang, Lei Yang, Chonghai Deng, Ningning Zhou, Kunhong Hu, Hai Yu, Jianguo Lv, Gang He
Abstract
Abstract CuBi 2 O 4 is identified as a promising photocathode in photoelectrochemical (PEC) water splitting systems. However, the PEC performance of CuBi 2 O 4 is far from expected due to the limited separation and transport efficiency of photogenerated carriers. To address the above issues, a cost‐effective ternary Cu:NiO X /CuBi 2 O 4 /CuO composite photocathode was designed. Firstly, a thin Cu:NiO X film was inserted between CuBi 2 O 4 and FTO conducting substrate as a hole‐selective layer, which promotes the transmission of photogenerated holes to the FTO substrate effectively. Furthermore, the modification of CuO film on the CuBi 2 O 4 electrode not only increases the absorption of sunlight and generates more photogenerated carriers, but also constitutes a heterojunction with CuBi 2 O 4 , creating a built‐in electric field, which facilitates the separation of electrons and holes, and accelerates the electrons transfer to electrode–electrolyte interface. The fabricated Cu:NiO X /CuBi 2 O 4 /CuO composite photocathode exhibits a surprisingly high photocurrent density of − 1.51 mA·cm −2 at 0.4 V versus RHE, which is 2.6 times that of the pristine CuBi 2 O 4 photocathode. The improved PEC performance is attributed to the synergy effect of the Cu:NiO X hole‐selective layer and the CuBi 2 O 4 /CuO heterojunction. Moreover, the combination with the BiVO 4 /CoS, an unbiased overall water splitting was achieved, which has a photocurrent of 0.193 mA·cm −2 .