Ultrasound-assisted synthesis of visible-light-driven Ag/g-C3N4 catalysts in a continuous flow reactor

Abstract

Size control of supported nanoparticles remains a challenge, especially in the presence of external fields. In this paper, an ultrasound-assisted method was developed for the continuous synthesis of visible-light-driven Ag/g-C3N4 catalysts with controllable sizes and narrow size distributions in a coiled flow inverter reactor. The catalytic performance was characterized by the photocatalytic water splitting, which was considered as a promising method to provide hydrogen fuel. Here, we investigated the synergy effect of output power of ultrasound, residence time, and Ag loading content on the characteristic and catalytic performance of the catalysts. With the increase of ultrasound output power (from 0 W to 120 W) and the decrease of residence time (from 140s to 17.5s), the size of silver nanoparticles becomes smaller, and the distribution is narrower. The higher catalytic activity was achieved for the catalyst under 60 W power, 1.22 times higher than that of the catalyst synthesized without ultrasound. Ag/g-C3N4 catalysts with higher Ag loading exhibited better catalytic activity, despite the bigger size of Ag nanoparticles. The results suggest that 7 wt% Ag/g-C3N4 catalysts synthesized under 60 W ultrasound power for 35s (residence time) exhibited the best photocatalytic activity for water splitting, which was 2.76 times higher than that of using pure g-C3N4.