Recent progress in NOx photocatalytic removal: Surface/interface engineering and mechanistic understanding

Due to the increased emission of nitrogen oxides (NOx) from flue gas and its high polluting effects on human health and the ecosystem, much attention is directed toward NOx monitoring, removal, and control. This work reviews the latest progress in NOx photocatalytic removal emphasizing the advancements in surface/interface engineering of photocatalytic materials considering the reaction mechanism and modifications for controlling the generation of the toxic intermediate. Defect chemistry, facet controlling, and stability of the photocatalytic systems are comprehensively discussed. The challenges/bottlenecks of the practical applications are also highlighted at the end. Indeed, the photocatalytic removal of NOx is still a significant challenge due to the remaining limitations. Herein, state of the art in utilizing the widely-used semiconducting materials such as TiO2 and g-C3N4-based photocatalysts are summarized, focusing on the eminent strategies to amend their performances under visible light. Also, we briefly survey the utilization of MOFs for NOx photoreduction, highlighting the unlikeness of such materials concerning the coincidence of the organic linkers as light sensitizers and the metallic nodes to intensify the transfer of photoinduced electrons. In addition to the concerns mentioned above in this review, so far, no serious consideration has been paid to the control of toxic by-products and intermediate species generation through NOx removal methodologies. Eventually, this report has been concluded with a summary and some perspectives on the advanced pathways to develop novel efficient nanomaterials for the removal of NOx hazards from the environment.