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

In this work, Ag/Bi5O7I nanocomposite was prepared and firstly applied in piezo/photocatalytic reduction of N2 to NH3 and methyl orange (MO) degradation. Bi5O7I was synthesized via a hydrothermal-calcination method and shows nanorods morphology. Ag nanoparticles (NPs) were photo deposited on the Bi5O7I 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 Bi5O7I presents the piezoelectric-like behavior, while the loading of Ag NPs can strengthen the character. Under ultrasonic vibration, the optimal Ag/Bi5O7I presents high efficiency in MO degra-dation. The degradation rate is determined to be 0.033 min -1, which is 4.7 folds faster than that of Bi5O7I. The Ag/Bi5O7I also presents a high performance in piezocatalytic N2 fixation. The piezocatalytic NH3 generation rate reaches 65.4 mmol 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 irra-diation simultaneously act on the Ag/Bi5O7I catalyst, higher performance in NH3 generation and MO degradation is observed. However, due to the weak adhesion of Ag NPs, some Ag NPs would fall off from the Bi5O7I 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.(c) 2021 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Commu-nications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

In this work, an Ag/Bi5O7I nanocomposite was prepared and used for the piezo/photocatalytic reduction of N2 to NH3 and methyl orange degradation for the first time. The addition of Ag nanoparticles to the Bi5O7I nanorods enhanced the spatial separation of charge carriers and improved the catalytic performance. Under ultrasonic vibration, the optimal Ag/Bi5O7I catalyst exhibited high efficiency in MO degradation and piezocatalytic N2 fixation. Additionally, simultaneous ultrasonic vibration and light irradiation further improved the performance. However, the weak adhesion of Ag nanoparticles resulted in their detachment under long-term ultrasonic vibration, leading to a reduction in the catalytic performance.