High piezo/photocatalytic efficiency of Ag/Bi5O7I nanocomposite using mechanical and solar energy for N2 fixation and methyl orange degradation

In this work, Ag/Bi 5 O 7 I nanocomposite was prepared and firstly applied in piezo/photocatalytic reduction of N 2 to NH 3 and methyl orange (MO) degradation. Bi 5 O 7 I was synthesized via a hydrothermal-calcination method and shows nanorods morphology. Ag nanoparticles (NPs) were photo deposited on the Bi 5 O 7 I nanorods as electron trappers to improve the spatial separation of charge carriers, which was confirmed via XPS, TEM, and electronic chemical analyses. The catalytic test indicates that Bi 5 O 7 I presents the piezoelectric-like behavior, while the loading of Ag NPs can strengthen the character. Under ultrasonic vibration, the optimal Ag/Bi 5 O 7 I presents high efficiency in MO degradation. The degradation rate is determined to be 0.033 min −1 , which is 4.7 folds faster than that of Bi 5 O 7 I. The Ag/Bi 5 O 7 I also presents a high performance in piezocatalytic N 2 fixation. The piezocatalytic NH 3 generation rate reaches 65.4 μmol L −1 g −1 h −1 with water as a hole scavenger. The addition of methanol can hasten the piezoelectric catalytic reaction. Interestingly, when ultrasonic vibration and light irradiation simultaneously act on the Ag/Bi 5 O 7 I catalyst, higher performance in NH 3 generation and MO degradation is observed. However, due to the weak adhesion of Ag NPs, some Ag NPs would fall off from the Bi 5 O 7 I surface under long-term ultrasonic vibration, which would greatly reduce the piezoelectric catalytic performance. This result indicates that a strong binding force is required when preparing the piezoelectric composite catalyst. The current work provides new insights for the development of highly efficient catalysts that can use multiple energies. • Ag/Bi 5 O 7 I composite was prepared by combining the hydrothermal and photodepostion process. • Ag/Bi 5 O 7 I composite can harvest vibration and solar energy for piezo-/photocatalytic N 2 fixation. • Ag/Bi 5 O 7 I presented much better performance in photo-/piezocatalytic N 2 fixation than pure Bi 5 O 7 I . • The loaded Ag improved catalytic performance by enhancing the charge separation. • The promotion effect of methanol scavenger in photo-/piezocatalytic N 2 fixation is verified.