Nano Metal Oxides Synthesized With Solid-liquid Phase Arc Discharge Method （SLPAD） And Their Application In The Photocatalytic Reduction Of CO₂

With a rapid development of industry and economy in the world, a series of environmental problems such as the "green-house effect" caused by the increasing of the concentration of CO2in the air have drawn much attention and concern of the national research scholars. Therefore, in recent years, researches for CO2fixation and transformation have gradually developed. As an important study branch, photocatalytic reduction of CO2to the useful chemicals or fuels which uses solar energy as power has attracted more attentions for its environmental protection ideas. In this way,"greenhouse effect" can be alleviated and the product generated can reduce the nuisance caused by the energy crisis, which can be described as killing two birds with one stone.Metal oxides have been favored by many researchers, due to its excellent performance in catalytic, non-toxic, easy preparation, low cost and other advantages in the choice of catalysts for the photocatalytic reduction of CO2. Several fabricating methods including hydrothermal processes, microemulsion, ball milling method, and molten salt synthesis method have been used to obtain metals oxides. However, the above synthetic methods are too complex and experimental conditions are too harsh, and often require organic surface active agent, which produces some pollution or toxic byproducts and causes serious environmental pollution. Therefore, looking for a simple, convenient, safe, low-cost and environmentally friendly method to synthesize metal oxide nanomaterials used in photocatalysis is of great significance.This article aims at exploring a simple method to prepare nanoparticles which meets the above requirements and investigation the nanoparticles in the application in the photocatalytic reduction of CO2. Hence, here we present a novel electrochemical method for forming nano-materials via a so-called solid-liquid phase arc discharge method (SLPAD) with the wire and NaN03aqueous solution. We did the following work:1. Highly ordered layer by layer TiO2nanotube arrays generated from a solid-liquid arc discharge process under ambient conditions in the absence of F. A possible fabricating mechanism was proposed. The current density on the contact surface of Ti wires and reaction solution play the key role of resulting in the products’ morphology. Then Tio2nanotube arrays were successfully applied to photocatalytic conversion CO2into useful hydrocarbon materials with H2O after loading with cocatalysts.2. A thin (-4nm), single-crystal WO3nanosheet was synthesized with a facile solid-liquid phase discharge (SLPAD) route. The edge of valence band and conduction band was2.48eV and-0.3eV, respectively. This indicates that the photogenerated electrons and holes in the irradiated WO3nanosheets can react with adsorbed CO2and H2O to produce CH4. The WO3nanosheets exhibit promising photocatalytic activity for reduction of CO2to CH4.