The Synthesis Of BiVO₄ Photocatalyst For Visible Light Photocatalytic Reduction Of Cr⁶⁺and Oxygen Evolution

Energy crisis and environmental pollution are two major issues caused by the excessive utilization of fossil fuels.Searching for clean and renewable energy is an effective way to solve these two issues.Photocatalytic water splitting is a new technology for the conversion of solar energy.The precondition for the application of photocatalytic technology is the development of photocatalyst with efficient photocatalytic activity of splitting water into H2 and O2 under visible light.Due to the slow kinetics involving multi-electron and multi-proton transfers,water oxidation is particularly demanding and requires high over potentials.Therefore,developing an efficient and practical photocatalyst that can oxidize water to O2 in a stable manner is critical for the successful construction of high performance photocatalytic system.On the other hand,the development of environmental-friendly,low-cost,stable and reusable photocatalyst for pollutant photodegradation is also a subject that is worth exploring.Monoclinic bismuth vanadate(m-BiVO4)with a narrow band gap of 2.4 eV has been widely applied for visible light photocatalytic evolution of O2 and organic matter degradation,due to its advantages of excellent stability,suitable energy band structure,non-toxic and environment-friend.Unfortunately,its specific applications still suffer from the poor quantum yield because of serious recombination of photogenerated electrons and holes.BiVO4 based heterostructures have been therefore designed to improve photogenerated charge separation efficiency.Herein,we synthesized hollow BiVO4/Bi2S3 cruciate heterostructures and BiVO4 microtubes and the photocatalytic activity of water splitting and reduction of Cr6+ were studied.The main content is as follows:(1)We reported a simple anion exchange method to synthesize hollow BiVO4/Bi2S3 cruciate heterostructures by hydrothermal treating BiVO4 cruciate flakes in Na2S aqueous solution.The proportion of BiVO4 to Bi2S3 can be easily adjusted by controlling the amount of Na2S during the anion exchange process.Purposeful spatial isolation of photogenerated electrons and holes from the heterojunction interface area significantly increases the survivability of the electrons crossing therein.Hollow structure of the special cruciate heterostructures also enlarges the area of electron transfer.Optimized loading of Bi2S3 broadedens visible-light adsorption range and is the prerequisite to get high photoreduction efficiency of Cr6+ions.(2)We reported a simple one-step hydrothermal method to synthesize BiVO4 microtubes with BiCl3,NH4VO3 and ethanolamine as the morphological regulator.The cross-section of the BiVO4 microtubes is an inner concave tetragonum.By analyzing the results of scanning electron microscope and transmission electron microscopy,the unique microtube is composed of four groups of BiVO4 {001} facets,and each group contains two slightly inward facets.In this paper,photocatalytic activity of oxidizing water to O2 was studied.