Uploaded October 2016 | Updated September 2026, 1 week ago
pubs.acs.org/doi/abs/10.1021/acs.langmuir.6b03263
A controlled aqueous growth of 1 µm flower-shaped ZnO particles with a hierarchical subset of exposed nano-sheets represented by {21̅0} crystal faces, followed by annealing at temperatures up to 1000 °C, is presented. The flower-shaped particles showed superior photocatalytic performance compared to the crystal faces of 20 nm ZnO nanoparticles. The photocatalytic reaction rate of the flower-shaped particles before annealing was 2.4 times higher per m2 compared with that of the nanoparticles with double specific surface area. Crystal surface defects and nano-sized pores within the flower-shaped particles were revealed by porosity measurement and electron microscopy. A heat treatment at 400 °C was found to be optimal for removal of nanoporosity/surface defects and impurities while retaining the hierarchical superstructure. The heat treatment resulted in a photo-degradation efficiency that increased by an additional 43 %, although the specific surface area decreased from 16.7 to 13.0 m2g-1. The enhanced photocatalytic effect remained intact under both acidic and alkaline environments owing to the {21̅0} crystal surfaces, which were less prone to dissolution than the nanoparticles. The photocatalytic performance relied on primarily three factors: the removal of surface impurities, the oxygen termination of the {21̅0} crystal faces, and the promotion of charge carrier lifetime by removal of lattice defects acting as recombination centres. The synthesis presented is an entirely hydrocarbon- and surfactant free (‘green’) preparation scheme, and the formation of the flower-shaped particles was favored solely by optimization of the reaction temperature after the correct nitrate salts precursor concentrations had been established.
#KenSweden
#Science
#ZincOxide
pubs.acs.org/doi/abs/10.1021/acs.langmuir.6b03263
A controlled aqueous growth of 1 µm flower-shaped ZnO particles with a hierarchical subset of exposed nano-sheets represented by {21̅0} crystal faces, followed by annealing at temperatures up to 1000 °C, is presented. The flower-shaped particles showed superior photocatalytic performance compared to the crystal faces of 20 nm ZnO nanoparticles. The photocatalytic reaction rate of the flower-shaped particles before annealing was 2.4 times higher per m2 compared with that of the nanoparticles with double specific surface area. Crystal surface defects and nano-sized pores within the flower-shaped particles were revealed by porosity measurement and electron microscopy. A heat treatment at 400 °C was found to be optimal for removal of nanoporosity/surface defects and impurities while retaining the hierarchical superstructure. The heat treatment resulted in a photo-degradation efficiency that increased by an additional 43 %, although the specific surface area decreased from 16.7 to 13.0 m2g-1. The enhanced photocatalytic effect remained intact under both acidic and alkaline environments owing to the {21̅0} crystal surfaces, which were less prone to dissolution than the nanoparticles. The photocatalytic performance relied on primarily three factors: the removal of surface impurities, the oxygen termination of the {21̅0} crystal faces, and the promotion of charge carrier lifetime by removal of lattice defects acting as recombination centres. The synthesis presented is an entirely hydrocarbon- and surfactant free (‘green’) preparation scheme, and the formation of the flower-shaped particles was favored solely by optimization of the reaction temperature after the correct nitrate salts precursor concentrations had been established.
#KenSweden
#Science
#ZincOxide
