It is of a great challenge to seek for semiconductor photocatalysts with prominent reactivity to remove kinetically inert dilute NO without NO emission. In this study, complete visible light NO oxidation mediated by O is achieved over a defect-engineered BiOCl with selectivity exceeding 99%. Well-designed oxygen vacancies on the prototypical (001) surface of BiOCl favored the possible formation of geometric-favorable superoxide radicals (•O) in a side-on bridging mode under ambient condition, which thermodynamically suppressed the terminal end-on •O associated NO emission in case of higher temperatures, and thus selectively oxidized NO to nitrate. These findings can help us to understand the intriguing surface chemistry of photocatalytic NO oxidation and design highly efficient NO removal systems.

Intelligent defect engineering to harness surface molecular processes is at the core of selective oxidation catalysis. Here, we demonstrate that the two-electron-trapped oxygen vacancy (VO) of BiOCl, a prototypical F center (VO ̋′′), is a superb site to confine O2 toward efficient and selective NO oxidation to nitrate. Stimulated by solar light, VO ̋′′ accomplishes NO oxidation through a two-electron charging (VO ̋′′ + O2 → VO ̋′′-O2 2–) and subsequent one-electron decharging process (VO ̋′′-O2 2– + NO → VO-NO3 – + e–). The back-donated electron is retrapped by VO to produce a new single-electron-trapped VO (VO′), simultaneously triggering a second round of NO oxidation (VO′-O2 + NO → VO-NO3 –). This unprecedented interfacial charging–decharging scheme alters the peroxide-associated NO oxidation selectivity from NO2 to NO3 – with a high efficiency and thus hold great promise for the treatment of risky NO x species in indoor air.

The electrocatalytic N2 reduction reaction (NRR) provides an environmentally benign approach for NH3 production that can be powered by renewable energy. It remains a challenge to understand the NRR mechanism and develop highly chemically active and selective yet low‐cost electrocatalysts. Herein, we report that N, P co‐doped porous carbon (NPC) with trace Fe (0.028 wt%) (Fe‐NPC) can serve as an electrocatalyst for the NRR in NaOH aqueous solution under ambient conditions. The Fe‐NPC catalyst exhibits significantly enhanced NRR activity compared with NPC, owing to the N, P co‐doped effect and trace Fe species active sites in the carbon material. The highest faradaic efficiency and ammonia yield of Fe‐NPC at −0.1 V vs. RHE reached 5.3 % and 4.36 μg h−1 mg−1cat. Furthermore, the electrochemical reaction mechanism on the Fe‐NPC electrode was investigated by electrochemical in situ Fourier transform infrared spectroscopy, and suggested an associative pathway.