Rational Design Of Materials Based On Titanium Oxide For Efficient CO₂ Reduction

The amount of CO₂ in the atmosphere is sharp increasing with the consumption of fossil fuels,which accelerates the pace of global warming.At present,using semiconductor photocatalysts to reduce CO₂ into carbon-containing energy materials is a feasible and effective way to solve the climate warming and fossil fuel consumption.An ideal photocatalyst should be not only stable but also has an appropriate energy band structure.The band gap should be narrow so that it can absorb enough solar energy,and meanwhile the photocatalyst should be stable enough so that it can be protected from the corrosion of the byproducts and light.Since Japanese researchers achieved producing hydrogen by using titanium oxide under ultraviolet light irradiation,scientists focused on designing functional photocatalysts for efficient photocatalytic reaction.Although great progress has been made in photochemical water splitting and carbon dioxide reduction in recent years,there is still a long way to go before it can be fully industrialized.Which is mainly due to the low absorption ability and insufficient charge transmission capacity of the photocatalyst.Based on this,we plan to effectively improve the optical absorption ability and photogenerated carriers transmission capacity of the composite by rationally constructing heterojunction and modifying the architecture,so as to finally achieve high CO₂ reduction efficiency.The specific experimental contents are as follows:?1?We prepared one-dimensional monocrystal r-TiO₂ nanoarrays by one-step hydrothermal method as a high-speed transmission channel for photogenerated carriers.And then deposit g-C₃N₄ quantum dots and Au quantum dots on the surface of the r-TiO₂ by impregnation method to construct an Au assisted C₃N₄/TiO₂ Z-type heterojunction.It is the rational construction of the Z-type heterojunction that effectively improves the optical absorption ability and the charge separation and transmission efficiency of the composite.Meanwhile,the band widening effect of g-C₃N₄ quantum dots leads to higher reduction capacity.The composite photocatalyst indicates a high CO₂ reduction performance without any sacrificial agents,which the yield rate of CO is 0.138?mol?cm^-2?h^-1,and the yield rate of CH₄ is 0.032?mol?cm^-2?h^-1,which is almost 4 times than that of r-TiO₂ nanoarrays.And the TiO₂ based thin film structure show great advantages in the collection and recycling performance after the chemical reaction.?2?We fabricated one-dimensional potassium titanate nanoarrays with acicular branch structure by one-step hydrothermal method,and the K⁺in the titanate were then replaced by H⁺by cyclic immersion in hydrochloric acid.After annealing,a large number of regular mesoporous can be formed in the body of nanoarrays,then we got the one-dimensional monocrystal porous anatase nanoarrays.The excellent porous single crystal structure not only effectively improves the light absorption performance of the catalyst,but also realizes efficient CO₂ reduction efficiency by virtue of the large specific surface and high carrier transport performance,which the yield rate of CO is0.129?mol?cm^-2?h^-1,and the yield rate of CH₄ is 0.019?mol?cm^-2?h^-1.In this work,we designed and synthesized TiO₂ based photocatalyst for efficient CO₂ reduction by constructing heterojunction and optimizing the material structure.And finally we realized excellent photocatalytic performance.These methods might provide guidance for the design of stable and efficient photocatalyst materials,and also provide solutions for the industrial production and practical application of photocatalysts.