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

The morphology-dependent property of crystal materials has aroused extensive attention 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 present superior catalytic performance to pristine PB microcubes and other PB intermediates with truncated corners or edges because of their high specific surface areas and adequate exposure of Fe^III-NC coordination active sites. In the reusability test, the reused PB-hpds present more efficient catalytic performance for rhodamine B decomposition compared with the pristine catalyst. According to more investigations, the reasonable mechanism is proposed that Fe^III-NC exhibits higher catalytic activity than Fe^II-CN in the specific coordination environment. The increased content of surface Fe^III-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 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.

Visible Light Driven Photoanodes for Water Oxidation Based on Novel r-GO/β-Cu₂V₂O₇/TiO₂ Nanorods Composites

This paper describes the preparation and the photoelectrochemical performances of visible light driven photoanodes based on novel r-GO/β-Cu₂V₂O₇/TiO₂ nanorods/composites. β-Cu₂V₂O₇ was deposited on both fluorine doped tin oxide (FTO) and TiO₂ nanorods (NRs)/FTO by a fast and convenient Aerosol Assisted Spray Pyrolysis (AASP) procedure. Ethylenediamine (EN), ammonia and citric acid (CA) were tested as ligands for Cu²⁺ ions in the aerosol precursors solution. The best-performing deposits, in terms of photocurrent density, were obtained when NH₃ was used as ligand. When β-Cu₂V₂O₇ was deposited on the TiO₂ NRs a good improvement in the durability of the photoanode was obtained, compared with pure β-Cu₂V₂O₇ on FTO. A further remarkable improvement in durability and photocurrent density was obtained upon addition, by electrophoretic deposition, of reduced graphene oxide (r-GO) flakes on the β-Cu₂V₂O₇/TiO₂ composite material. The samples were characterized by X-ray Photoelectron Spectroscopy (XPS), Raman, High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Wide Angle X-ray Diffraction (WAXD) and UV–Vis spectroscopies. The photoelectrochemical (PEC) performances of β-Cu₂V₂O₇ on FTO, β-Cu₂V₂O₇/TiO₂ and r-GO/β-Cu₂V₂O₇/TiO₂ were tested in visible light by linear voltammetry and Electrochemical Impedance Spectroscopy (EIS) measurements.