Preparation Of Morphology-controlled Photocatalysts And Their Photocatalytic Performance Of CO₂ Reduction Study

In order to continuously pursue higher economic benefits,human emissions of CO₂continue to increase.In addition,due to the limited reserves of fossil fuels,with the continuous development and utilization of human beings for so many years,the fossil energy crisis has gradually emerged.In order to cope with this situation,it is urgent to develop new energy utilization technologies.In this case,the photocatalytic CO₂ reduction reaction is an extremely promising research direction under the background of global warming.But current catalysts have many drawbacks,for example most photocatalysts can only promote the two-electron reduction process to generate CO,and it is difficult to produce eight-electron product CH₄,which is more valuable and can store more solar energy.The preparation of catalysts occupies an extremely important position in the development of this technology,As one of the important modification methods of photocatalysts,morphology control will undoubtedly attract everyone’s attention.In this work,the morphology of the photocatalyst was regulated by simple means,and a series of studies were carried out on its photocatalytic CO₂reduction performance.The specific work is as follows:（1）we prepared porous silver cyanamide nanocrystals with tunable morphologies via a facile synthesis strategy.Compared with ball/rectangular plate（RAP）and ball/leaf-like plate（SAP）,the ball/porous leaf-like plate（LAP）can provide more internal reaction microenvironment,which is not only conducive to the transport of photoinduced charge carriers,but also can expand the active sites for photocatalytic CO₂ reduction.Moreover,the suitable band gap of LAP sample can capture more visible light to provide more photoinduced electron-hole pairs to participate in the reduction reaction.Consequently,the LAP sample can convert CO₂ to CH₄ with remarkable activity and high selectivity（nearly 100%）without cocatalyst and photosensitizer under visible light irradiation.This work provides a promising way to design new photocatalysts for various applications in solar energy conversion.（2）A series of organoborane molecules with different conjugated systems were prepared by organic synthesis strategy,and they were prepared into quantum dots and porous g-C₃N₄to construct 0D/2D composites.The 0D/2D composite has great photo-generated electron transfer ability and good photocatalytic performance under illumination.After 5 h of illumination,its carbon monoxide yield is 320.09μmol g^-1 h^-1,which is 23.9 times that of porous g-C₃N₄(μmol g^-1 h^-1).The yields of hydrogen and methane were also significantly improved,which were 36.4 times and 10.1 times higher than those of porous g-C₃N₄,respectively.The experimental results show that the introduction of different conjugated systems can greatly affect the ability of B atoms to activate CO₂molecules,and significantly enhance the photocatalytic activity.