Synthesis of Cs3PMo12O40/Bi2O3 composite with highly enhanced photocatalytic activity under visible-light irradiation.

A novel visible-light-active Cs3PMo12O40/Bi2O3 (CsPMo/Bi2O3) composite was prepared by a simple dissolution-precipitation method. The as-prepared samples were characterized by XRD, XPS, FT-IR, SEM, UV-Vis DRS, N2 adsorption-desorption isotherms and electrochemical analysis. The results revealed that Bi2O3 was successfully modified by trace CsPMo. After the addition of H3PMo12O40 acid (HPMo), the surface of Bi2O3 can be roughed. Subsequently, the presence of Cs2CO3 can neutralize the protons of HPMo forming CsPMo precipitate on Bi2O3. Comparing to naked Bi2O3 and CsPMo, the binary composite exhibited many beneficial characteristics in charge generation and separation, such as formation of p-n heterojunction, decreased band gap, enhanced photocurrent response and greatly reduced charge transfer resistance. The photocatalytic activities of the as-prepared samples were evaluated by the degradation of phenol under visible light. The calculated pseudo-first-order rate constants for phenol degradation were 2.7 and 14.8 times relative to that on Bi2O3 and CsPMo, respectively. Dramatically enhanced photocatalytic performance can be observed when the optimal CsPMo/Bi2O3 composite (2.5% CsPMo) was applied. The major active species involved in the degradation process are in the following order: superoxide radical (O2-) > hydroxyl radical (OH) ≈ hole (h+). Besides, the CsPMo/Bi2O3 composite also displayed good stability in cyclic experiments.