Photocatalytic NOx removal and recovery: progress, challenges and future perspectives

The excessive production of nitrogen oxides (NOx) from energy production, agricultural activities, transportation, and other human activities remains a pressing issue in atmospheric environment management. NOx serves both as a significant pollutant and a potential feedstock for energy carriers. Photocatalytic technology for NOx removal and recovery has received widespread attention and has experienced rapid development in recent years owing to its environmental friendliness, mild reaction conditions, and high efficiency. This review systematically summarizes the recent advances in photocatalytic removal, encompassing NOx oxidation removal (including single and synergistic removal and NO3- decomposition), NOx reduction to N-2, and the emergent NOx upcycling into green ammonia. Special focus is given to the molecular understanding of the interfacial nitrogen-associated reaction mechanisms and their regulation pathways. Finally, the status and the challenges of photocatalytic NOx removal and recovery are critically discussed and future outlooks are proposed for their potential practical application.