Research On Synthesis And Visible Light Photocatalytic Propertiees Of Tin Dioxide-based Nanomaterials

Photocatalysis is a research direction that can solve environmental pollution and energy crisis by using solar energy.Degradation of organic pollutants by semiconductor photocatalysts is an important component of photocatalysis.Tin dioxide?SnO₂?is a highly promising semiconductor photocatalyst that has been widely used in varieties of photocatalytic reactions.However,similar to TiO₂,SnO₂is a wide bandgap semiconductor,and the low utilization of visible light limits its application in photocatalytic reactions.Here,a series of tin dioxide-based photocatalysts with visible light catalytic activities were prepared by introducing oxygen vacancies and doping of metal ions.The oxygen vacancy-rich SnO₂ quantum dots photocatalysts were successfully synthesized by the vapor hydrolysis method.Due to the introduction of oxygen vacancies,the light absorption range of the as-synthesized SnO₂ quantum dots is extended to the visible region.The formation of defect energy levels contributes to the separation and transfer of photogenerated electron holes.The specific surface areas of SnO₂ quantum dots are much larger than that of commercial SnO₂,which is about 11 times,and more active sites are obtained.Methyl orange solution was used as the typical pollutant for degradation.It is found that the prepared SnO₂ quantum dots have much higher degradation activity for methyl orange than commercial SnO₂.By changing the synthesis temperature,it is found that the photocatalytic degradation activity is the best at 160?.The photocatalytic activity of SnO₂ quantum dots synthesized at 160? is 259.84 and 182.70 times higher than that of commercial SnO₂ and P25,respectively.Finally,the main active substances in photocatalytic reaction are identified as superoxide radicals and holes by free radical trapping experiments.According to the results,a possible photocatalytic mechanism is proposed.Co-doped SnO₂ nanosheets were fabricated via hydrothermal method.The photocatalytic degradation activity of Co-doped SnO₂ nanosheets on methyl orange is significantly higher than that of commercial SnO₂ and the best Co doping amounts is 3%.The photocatalytic degradation rate of undoped SnO₂ nanosheets and the 3%Co/SnO₂ nanosheets are 30.4 times and 133.8 times of the commercial SnO₂ Oxygen vacancies form defect energy levels in the energy bands of SnO₂ semiconductor nanosheets.The introduction of Co further increased the defect concentrations,effectively promoted the transfer of photogenerated electrons,and suppressed the recombination of electrons and holes,which also corresponded to the photocatalytic performance.The main active substance in photocatalytic reaction was determined to be superoxide radical by free radical trapping experiment.Holes and hydroxyl radicals play an auxiliary role in the photocatalysis,and a possible photocatalytic mechanism is proposed.