Tunable microstructure of α-Ni(OH)2 for highly-efficient surface adsorbates activation to promote catalytic NO oxidation

Abstract

The catalytic oxidation technology has attracted extensive consideration in the matter of NOx removal on account of its economical and environmentally-friendly process. However, the lack of active sites, inadequate surface adsorbates activation and generation of toxic byproduct limit its practical application. Herein, we reported the synthesis of α-Ni(OH)2 catalysts with tunable microstructure by using different solvents. Among them, α-Ni(OH)2 prepared with propylene glycol as the solvent (Ni-PG) delivered the highest activity for NO oxidation without any toxic NO2 byproduct generation. The propylene glycol played an important role in improving the unique α-Ni(OH)2 surface area and layer spacing, which favored the adsorption of pollution gas and provided more active sites and new reaction channels. In addition, the incorporation of Ni3+ induced the development of an O-exposed surface. The combination of theoretical calculations and experiments verified that NO could be activated by the O-exposed surface to form NO+ while O2 could be activated by the Ni-PG surface H atoms, promoting sufficient oxidation of both NO and NO2 to produce NO3–. The increased specific surface area and active sites, new reaction routes, as well as surface adsorbates activation ability were therefore responsible for the improved NOx oxidation over Ni-PG and completely impeded the generation of toxic NO2 byproduct, showing that the Ni-PG possesses tremendous potential for air purification. This work provides a new insight into surface adsorbates activation for catalytic NOx oxidation.