Cooperation or competition between piezocatalysis and photocatalysis of Bi₄Ti₃O₁₂ nanoflakes

Co-utilization of solar and mechanical vibration energy via the piezo-photo bicatalysis is a new-emerging strategy for the management of environmental pollution. The combined bicatalysis is always expected to have a higher degradation rate than the sole catalysis. In this work, piezocatalysis coupled with photocatalysis has been applied to Bi₄Ti₃O₁₂ nanoflakes to check their synergistic effect. It was found that the dual catalysis including sonication exhibits an inferior degradation rate to the only piezocatalysis, which is contrary to the results reported in many references. However, if the piezoelectric stress is only afforded by a mechanical stirrer, the combined piezo-photo bicatalysis has a remarkable synergistic enhancement effect than the individual one. The radical trapping experiments were performed to identify the reactive active species involved in the decomposition of Rhodamine B (Rh B). The competition or cooperation of main active species in dual catalysis is suggested to clarify the underlying mechanism dominating the hybrid bicatalysis degradation efficiency. Additionally, the universality of the mechanism is also confirmed for treating Methyl Blue (MB) and Methyl Orange (MO).