Prussian Blue Microcrystals with Morphology Evolution as High-Performance Photo-Fenton Catalyst for Degradation of Organic Pollutants.

The morphology-dependent property of crystal materials has aroused extensive attentions and raised high requirements for subtly tailoring the morphology of micro-/nanocrystals. Herein, we develop an in-situ etching method for preparation of Prussian blue (PB) microcrystals with morphology evolution by progressively increasing the concentration of chloroplatinic acid in the reaction system. These PB microcrystals with controllable morphologies are employed as photo-Fenton reagents to degrade organic pollutants. PB hexapods (PB-hpds) and PB hexapod stars (PB-hpss) present superior catalytic performance to pristine PB microcubes (PB-cubs) and other PB intermediates with truncated corners or edges due to their high specific surface areas and adequate exposure of FeIII-NC coordination active sites. In the reusability test, the reused PB-hpds present more efficient catalytic performance for Rhodamine B (RhB) decomposition compared with the pristine catalyst. According to more investigations, the reasonable mechanism is proposed that FeIII-NC exhibits higher catalytic activity than FeII-CN in the specific coordination environment. The increased content of surface FeIII-NC coordination active sites is the key factor in accelerating the decomposition of H2O2 and enhancing the photo-Fenton performance of PB-hpds. Several operating parameters including catalyst dosage, H2O2 concentration, pH value, and reaction temperature are evaluated in detail. Classical quenching experiments and electron paramagnetic resonance (EPR) measurements further reveal that HO· should be responsible for high performance of catalysts. This work will be significant for tailoring the morphology of the materials and arousing more attention to enhance the stability and reusability of catalysts.