Superoxide anion and singlet oxygen dominated faster photocatalytic elimination of nitric oxide over defective bismuth molybdates heterojunctions

Establishing an ideal photocatalytic system with efficient reactive oxygen species (ROS) generation has been regarded as the linchpin for realizing efficient nitric oxide (NO) removal and unveiling the ROS-mediated mechanism. In this work, a novel oxygen-deficient 0D/1D Bi3.64Mo0.36O6.55/Bi2MoO6 heterojunctions (BMO-12-H) were successfully synthesized under the enlightenment of clarified crystal growth mechanism of bismuth molybdates. Because of the synergies between defect-engineering and heterojunction-construction, BMO-12-H demonstrated improved photoelectrochemical properties and O2 adsorption capacity, which in turn facilitated the ROS generation and conversion. The enhancement of •O2- and 1O2 endowed BMO-12-H with strengthened NO removal efficiency (59%) with a rate constant of 12.6*10-2 min-1. A conceivable NO removal mechanism dominated by •O2- and 1O2 was proposed and verified based on the theoretical calculations and in-situ infrared spectroscopy tests, where hazardous NO was oxidized following two different exothermic pathways: the •O2--induced NO → NO3- process and the 1O2-induced NO → NO2 → NO3- process. This work offers a basic guideline for accelerating ROS generation by integrating defect-engineering and heterojunction-construction, and provides new insights into the mechanism of efficient NO removal dominated by •O2- and 1O2.