Vacancy-Rich and Porous NiFe-Layered Double Hydroxide Ultrathin Nanosheets for Efficient Photocatalytic NO Oxidation and Storage

An appealing strategy in the direction of circular chemistry and sustainable nitrogen exploitation is to efficiently convert NOx pollutants into low-toxic products and simultaneously provide crop plants with metabolic nitrogen. This study demonstrates that such a scenario can be realized by a defect- and morphology-coengineered Ni-Fe-layered double hydroxide (NiFe-LDH) comprising ultrathin nanosheets. Rich oxygen vacancies are introduced onto the NiFe-LDH surface, which facilitate charge carrier transfer and enable photocatalytic O₂ activation into superoxide radicals (^•O₂^-) under visible light. ^•O₂^- on NiFe-LDH thermodynamically oxidizes NO into nitrate with selectivity over 92%, thus suppressing dangerous NO₂ emissions. By merit of abundant mesopores on NiFe-LDH ultrathin nanosheets bearing a high surface area (103.08 m²/g), nitrate can be readily stored without compromising the NO oxidation reactivity or selectivity for long-term usage. The nitrate species can be easily washed off the NiFe-LDH surface and then enriched in the liquid form as easy-to-use chemicals.