Purification and Value-Added Conversion of NOx under Ambient Conditions with Photo-/Electrocatalysis Technology

As primary air pollutants from fossil fuel combustion, the excess emission of nitric oxides (NO_x) results in a series of atmospheric environmental issues. Although the selective catalytic reduction technology has been confirmed to be effective for NO_x removal, green purification and value-added conversion of NO_x under ambient conditions are still facing great challenges, especially for nitrogen resource recovery. To address that, photo-/electrocatalysis technology offers sustainable routes for efficient NO_x purification and upcycling under ambient temperature and pressure, which has received considerable attention from scientific communities. In this review, recent advances in photo-/electrocatalysis technology for the purification and value-added conversion of NO_x are critically summarized. The target products and reaction mechanisms for NO_x conversion systems, together with the responsible active sites, are discussed, respectively. Then, the realistic environmental practicability is proposed, including strict performance evaluation criteria and application in realistic conditions for NO_x purification and upcycling by the application of photo-/electrocatalysis. Finally, the current challenges and future opportunities are proposed in terms of catalyst design, NO_x conversion enhancement, reaction mechanism understanding, practical application conditions, and product separation techniques.