Preparation Of Hierarchical BiOCl Composites And Its Photocatalytic Properties

Nowadays,the world energy crisis and environmental pollution,including water and air pollution,have become the major problems in human life.According to the requirements of human sustainable development,it is imperative to develop a clean,sustainable and carbon neutral technology to solve energy and environmental problems.The general technologies of industrial wastewater treatment include activated carbon adsorption,solvent extraction and ozone-related chemical oxidation.However,these technologies are prone to secondary pollution and even produce a large number of harmful by-products.Then,semiconductor photocatalysis is a promising alternative technology that can convert CO₂and N₂into useful solar fuels such as hydrocarbons and ammonia,and efficiently degrades organic pollutants in water.It is regarded as one of the most promising and practical solutions to current and future energy and environmental problems because of its low cost,high efficiency and ability to utilize solar energy.The advances in photocatalysis over the past decade have sparked interest in using solar energy to treat sewage and fix N₂and CO₂.However,there are still some shortcomings to be solved in photocatalytic applications,such as low conversion efficiency and low selectivity of catalytic products.Therefore,in recent years,the bismuth-based halogen oxide(Bi OX,X=Cl,Br or I)has been widely concerned by the scientific community for its unique optical and electrical properties.In this paper,we are going to study Bi OCl semiconductor materials and their application in photocatalytic degradation of organic pollutants and fixation of N₂and CO₂.1.The Bi OCl semiconductor materials with three morphologies(flake-shaped,flower-shaped and hollow spherical)were synthesized by a simple method,and the effects of different morphologies on the properties of as-prepared photocatalyst were studied.Results showed that the hollow spherical Bi OCl has the best photocatalytic performance.Therefore,in order to further improve the photocatalytic performance of single material,the hollow spherical Bi OCl semiconductor composite doped with Pt and N(Pt/N-Bi OCl)was synthesized by a simple one-step hydrothermal method.The results of the characterization experiments show that the optical response and the photogenerated electron-hole separation efficiency of the material after doping N and Pt increase obviously,and the electron-hole recombination is effectively reduced.The photocatalytic degradation efficiency of as-prepared samples for organic pollutants(ciprofloxacin,CIP and rhodamine B,Rh B)were investigated.When the doping amounts of Pt and N were 1%and 0.25%(wt.%)respectively,the Pt₁/N_0.25-Bi OCl composite showed the best photocatalytic performance.The results showed that the degradation rates of Rh B and CIP by the sample reached 97.9%and 81.8%respectively,which was about twice that of single Bi OCl.2.The Z-scheme g-C₃C₄/Bi OCl heterojunction material was successfully synthesized by one-step hydrothermal method using stripped g-C₃N₄nanosheets as precursors,and then the ternary composite material was prepared by further loading graphene quantum dots(GQDs).The photocatalytic performance was evaluated by photofixation of N₂under the mild conditions.The effect of doping amount of GQDs and g-C₃N₄on photocatalytic performance was investigated,and the results showed that the ternary materials have the best photocatalytic performance when the doping amounts of GQDs and g-C₃N₄are 3%and 15%(wt.%)respectively.According to the results,it can be inferred that the Z heterojunction structure formed between g-C₃N₄and Bi OCl can promote the separation of photogenerated electron-hole pairs,and GQDs can accelerate the electron transport,thus enhancing the photocatalytic performance of the material.3.A unique chlorophyll and Mg co-modified Bi OCl composite was synthesized,and its photocatalytic performance of CO₂reduction to solar fuel was evaluated under a mild conditions.Firstly,the influence of Chl loading on the CO₂reduction efficiency of as-prepared photocatalyst was studied.As a result,due to the photosensitivity of Chl,the light absorption capacity,electron transfer rate and photocatalytic performance were further improved after the introduction of Chl.Next,the effect of Mg on the catalytic activity was also studied.Then,we can conclude that the Mg loading increased the light absorption capacity and photocatalytic stability of materials.The best photocatalytic performance was achieved when the doping amount was 0.1%.Besides,the photocatalytic mechanism of the composites was also analyzed.