Mechanism analysis of photocatalytic activity on Semiconductor-Type-Modulated heterojunctions

The construction of heterojunction is one of the most popular strategies to improve the performance of photocatalysts, but the influence of heterojunction types on their photocatalytic behaviors is rarely investigated. Here, the p-n and n-n type heterojunctions were constructed through combining p-type BiOBr (p-BOB) or n-type BiOBr (n-BOB) with n-type g-C3N4 (CN), and their photocatalytic performances were evaluated through RhB degradation and production of H2 in comparison with that of pure n-/p- BiOBr semiconductor. The n-n type heterojunction n-BOB/CN exhibits more excellent photocatalytic performance than that of p-n type heterojunction p-BOB/CN though the latter presents more efficient separation of photogenerated carriers with the strongest photocurrent response and the smallest impedance under the driven of strong built-in electric field. The step-scheme (S-scheme) charge transfer mechanism in n-BOB/CN heterojunction was proposed based on the calculation of work functions and the corresponding valance or conduction band potential, which is responsible for the more excellent photocatalytic performance of n-BOB/CN than that of p-BOB/CN.