**4. Conclusions**

In conclusion, BiOCl/NaNbO3 piezoelectric composites are synthesized via a twostep hydrothermal route. Under UV–vis light and ultrasonic exposure, the BN-3 for piezo-photocatalytic decomposition of RhB demonstrate remarkable piezo-photocatalytic performance than that of BiOCl and NaNbO3 component due to the heterojunction construction. Furthermore, the piezo/photodegradation rate of RhB for BN-3 is higher than that of piezocatalysis and photocatalysis, indicating the synergistic effect of piezocatalysis and photocatalysis plays a significant role in the degradation process. Some issues, such as the specific promotion mechanism of the NaNbO3 and BiOCl of the contribution of the piezo-photocatalytic performance, need to be further investigated for better understanding. However, this work provides a feasible approach for the development of efficient piezoelectric photocatalysts for heterojunction construction.

**Author Contributions:** Conceptualization, C.W. and F.L.; methodology, C.W.; investigation, L.L.; resources, C.W. and F.L.; data curation, L.L.; software, L.L.; W.C., J.Y. and W.L.; writing original draft preparation, L.L.; writing review and editing, L.L., C.W. and F.L.; supervision, C.W. and F.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 12174001, 12104001, and 51872001).

**Data Availability Statement:** Data available in a publicly accessible repository. The data presented in this study are openly available in [repository name e.g., FigShare] at [doi], reference number [reference number].

**Conflicts of Interest:** The authors declare no conflict of interest.
