Research On The Strategy And Mechanism Of Improving The Activity Of Carbon Nitride Photocatalysis To Generate Fuel

As the world environment and traditional fossil energy problems become more and more promient,the search for a clean,renewable,cheap,safe and feasible energy source to solve the problem of depletion of fossil fuels and environmental pollution has attracted much attention.Semiconductor photocatalytic technology takes semiconductor photocatalyst as the core and utilizes inexhaustible solar energy resources to effectively realize the conversion production of new energy sources such as water decomposition and hydrogen production and carbon dioxide reduction to methane,etc.,and can effectively eliminate environmental pollution.extensive attention.At present,the development of efficient and inexpensive visible light catalysts is the focus of research in the field of photocatalysis.Two-dimensional nanosheet material Graphite phase carbonitride?g-C₃N₄?is widely considered to be a potential photocatalyst material as an environmentally friendly and inexpensive product.However,defects such as electrons and holes are liable to recombine and surface catalytic activation is poor,which seriously affects the visible light catalytic activity of g-C₃N₄.Therefore,this paper aims to improve the precious metals?Pt,Ag,Au?and transition metals?Ni,Fe,Co?by boric acid surface pretreatment for the key scientific problems of g-C₃N₄ visible light charge separation and surface catalytic activation.A new strategy was constructed on the surface of single-atom cocatalyst dispersed on the surface of g-C₃N₄,and its photo-generated charge transfer,separation and surface catalytic activation mechanisms were deeply explored.The specific experiment is divided into the following two parts:First,the general precious metal Pt was selected as a cocatalyst to improve the dispersion of Pt on the surface of g-C₃N₄ and reduce the particle size by regulating the modification amount of inorganic boronic acid on the surface of g-C₃N₄.The surface photovoltage spectrum,fluorescence spectrum and hydroxyl radical concentration test showed that the photo-generated charge separation of Pt-g-C₃N₄ could be effectively improved by the pretreatment of boric acid.The sample 0.5Pt-5B-CN was the best.Photocatalytic carbon dioxide reduction and hydrogen production activity test results show that the activity of boric acid is much higher than that of purely precious metal,which may be due to the surface modification of boric acid effectively increasing the surface dispersion of Pt and greatly reducing the particle size of Pt.Even to the result of a single atom.Finally,the superiority of Pt is determined by comparing the activity of different noble metal atoms.The results of this study provide new ideas for the subsequent improvement of the photocatalytic activity of g-C₃N₄ and the work of monoatomic.Secondly,the nanocomposite of YNi-5B-CN was designed and synthesized by wet chemical method.The existence of single atom of Ni was proved by spherical electron microscopy and synchrotron radiation,and the fluorescence spectrum was based on the instantaneous/steady-state surface photovoltagespectrum.Hydroxyl radical photoluminescence spectroscopy determined that the charge separation ability was significantly improved,and the activity of photocatalytic hydrogen production and photocatalytic carbon dioxide conversion was also significantly enhanced.More notably,by IR,TG-Mass and XPS water adsorption,it was found that nickel atoms can not only regulate electrons,but also improve the adsorption capacity of YNi-5B-CN nanocomposites for water,resulting in a significant increase in catalytic activity.On this basis,the paper also explores the existence of hydrogen in the product in the presence of photocatalytic methanol,which is mainly derived from water,and a small part is derived from methanol.Methanol is mainly present as a sacrificial agent in the catalytic reforming process.Finally,it is verified by comparative experiments that the presence of boric acid is more favorable for the activity,and the activity of Ni is better than that of Fe and Co under the same conditions.