Preparation Of G-C₃N₄ Based Photocatalyst And Its Photocatalytic Performance Under Visible Light

Recently,semiconductor photocatalyst has been widely applied to resolve intractable environmental issuses using abundant solar energy.However,only a mount of UV-light in natural light sources can be ultilized due to the opitical limitations of conventional photocatalyst materials with wide band gap?for instance,TiO₂ is about 3.2 eV?,so the photocatalytic performance of photocatalysts can be limited in large extent.Therefor,it is urgent to find a photocatalyst that is high-efficiency and can take an effect under visible light.The band gap of graphite-like carbon nitride?g-C₃N₄?is².7 eV,so g-C₃N₄ can degrade organic polluent under visible light irradiation.However,the fast recombination of photogenerated electrons and holes inhibits the photocatalytic performance of g-C₃N₄.Consequently,we have made the following studies of g-C₃N₄ to overcome its fast recombination of photogenerated electrons and holes:?1?Efficinet graphene/band structure modified g-C₃N₄?Gr/PI?heterojunction photocatalyst was preparated by sonochemical method.Gr/PI has a good degradation effection on Rhodamine B?RhB?.The results showed that the kinetic constant?k?of RhB removal with Gr/PI catalyst was 0.0401 min^-1,which was 1.72 times and 1.60 times as that of PI(0.0233 min^-1)and Gr/g-C₃N₄(0.0250min^-1),respectively.The excellent photocatalytic ability of Gr/PI was mainly attributed to the effective separation of photogenerated electrons and holes.The trapping experiments of radicals showed that·O₂^-and·OH were the main reactive species for the photocatalytic degradation of RhB.?2?Carbon vacancies modified g-C₃N₄ photocatalyst?V_C-C₃N₄?was successfully preparated by calcination method under high temperature,which had a good degradation effection on bisphenol A?BPA?.The results showed that the k of BPA photodegradation with V_C-C₃N₄(0.0056 min^-1)was 1.65 times as that of pristine g-C₃N₄(0.0034 min^-1).The enhanced photocatalytic performance of V_C-C₃N₄ was ascribed to critical role of carbon vacancies:on the one hand,carbon vacancies served as the reservoir of photogenerated electrons to inhibit the recombination of photogenerated holes and electrons;On the other hand,carbon vacancies as conversion centers transferred trapped photogenerated electrons to absorbed O₂ for generation of abundant superoxide radical?·O₂^-?,which took a dominant effect in the photocatalytic degradation process.?3?WO₃/lamellar g-C₃N₄?WO₃/t-C₃N₄?photocatalyst was preparated by calcination,which could efficiently degrade RhB.The results showed that the photocatalytic capacity of WO₃/t-C₃N₄ was gradually enhanced with the increase of WO₃.The k of RhB photodegradation with 30%WO₃/t-C₃N₄(0.040 min^-1)was 1.33,1.74 and 2.67 times as that of 20%WO₃/t-C₃N₄(0.030 min^-1),10%WO₃/t-C₃N₄(0.023 min^-1)and t-C₃N₄(0.015 min^-1),respectively.The enhanced photocatalytic capacity was attributed to the improved adsorption ability of WO₃/t-C₃N₄ and the advantage of WO₃/t-C₃N₄ heterojunction which could inhibit the fast recombination of photogenerated electrons and holes.The trapping experiments of radicals confirmed that·O₂^-and·OH were the main reactive species for the photocatalytic degradation of RhB...