| Graphitic carbon nitride(g-C3N4)has various advantage such as simple fabrication process,cheap feedstocks,low band gap(2.7 eV)and visible-light-response,which make it attract worldwide attention.However,the low specific surface area and fast recombination of photo-induced carriers,limitting the application of g-C3N4 in photocatalysis field.Nanosizing g-C3N4 is one of the effective methods to improve its quantum efficiency.In recent years,the mesoporous g-C3N4,which possesses large surface area,low mass transfer resistance and efficient separation of photogenerated carriers,overcome the intrinsic deficiency of bulk g-C3N4 in some degree?and often shows enhanced photocatalytic performance.Generally,the mesoporous g-C3N4 is prepared by template method.Those templates,including SBA-15?core/shell SiO2 and SiO2 NPs etc,which have regular morphology.However,there are still some shortcomings:1)The template is expensive due to the synthesis process of templates are complicated;2)the insufficient combination degree between the templates and the precursor of g-C3N4,resulting in the relatively lower surface area of obtained mesoporous g-C3N4.The foam-like graphitic carbon nitride was synthesized by template method using melamine as raw material and the cheap sepiolite as hard template,respectively.Basis on this,a series of modified foam-like graphitic carbon nitride by varied methods and their photocatalytic activity were investigated.The detail work is as follows:(1)The form-like g-C3N4 was fabricated by template method using the cheap sepiolite as hard template and in-situ formation of polydopamine coating layer as modification.The results showed that polydopamine coating could act as adhesives,which could improve the combination degree between template and melamine,leading increase of the specific surface area of foam-like graphitic carbon nitride.Furthermore,the specific surface area of the obtained sample increases with the increasing of polydopamine modified sepiolite.When polydopamine modified sepiolite:melamine is 2:1,the specific surface area of the foam like g-C3N4 is as high as 389.2 m2/g and the visible light driven H2 evolution rate can reach up to 1061.87?Lmol·g·h-1,,which is?7 times greater than that of bulk g-C3N4(151.2 ?gmol·g-1·h-1)and 2.6 times higher than that of graphitic carbon nitride synthesized by unmodified sepiolite,respectively.(2)The ultrafine platinum nanoparticles,acting as co-catalyst,were fabricated using the channel of sepiolite as nano-reactor firstly.Then,a foam-like g-C3N4 with the highly dispersed platinum nanoparticle cocatalyst embeded in the cavity was obtained.The results showed that the visible light driven H2 evolution rate of the as-prepared platinum nanoparticle embeded foam-like g-C3N4 is 2 times greater than that of foam-like g-C3N4 loading Pt by in-situ photo-depostion.The optimal Pt mass percent is 3.7%,giving a visible-light driven H2-production rate of 2270.3?mol·g-1·h-1,which is?15 times greater than that of bulk g-C3N4(151.2 ?mol·g-1·h-1).(3)Phosphorus doped foam-like g-C3N4 was prepared by thermal pyrolysis the mixture of foam g-C3N4 and NaH2PO2.When the mass ratio of foam g-C3N4 and NaH2PO2 was 4:1,the as-prepared samples exhibited optimal photocatalytic activity and the visible light driven H2 evolution rate can reach up to 1844.6 ?.m0ol·g-1·h-1,which is?1.7 times greater than foam g-C3N4.The results indicate that phosphorus was successfully doped into the foam-like g-C3N4,leading to a change of band gap of g-C3N4 and an enhancement of solar light utilization.(4)Aiming to development of cos-effective cocatalyst alternative noble metal Pt,a single atom CoPx site coordinated with foam-like g-C3N4 were constructed.The results showed that single CoPx site confined on g-C3N4 could both promote the separation of charge and surface catalytic transfer of carriers.The optimal CoPx content is 3%,giving an H2-production rate of 682.82 ?pmol·g-1·h-1 which is as?60 times as the pure foam g-C3N4 without co-catalyst. |
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