Solid-state Synthesis Of Carbon-based Nanocatalysts And Their Applications

Carbon nanomaterials(graphene,carbon nanotubes,carbon quantum dots,etc.)are a new type of catalysts or catalyst support materials,which have broad application prospects in photocatalysis,electrocatalysis,ammonia synthesis,catalytic hydrogenation,ammonia decomposition for hydrogen production.At present,the preparation of traditional carbon-based nanocatalysts is mostly using liquid phase synthesis method,which is difficult to control the composition and dispersibility of the catalysts due to the constraints of the mixed precursor,and the method is complicated and the cost is high.Layered metal hydroxides have uniform structure and tunable compositions,and have attracted widespread attentions in the field of nanomaterial synthesis.In this thesis,highly-dispersed and purity carbon-based nanocatalysts are synthesized by a one-step solid-state synthesis method using organic intercalated layered metal hydroxide as a single precursor.The catalysts are characterized and applied in detail.The detail research contents are as follows:1.Using cheap sodium salicylate and zinc nitrate as raw materials,salicylic acid intercalated layered zinc hydroxide nanosheets is prepared in the aqueous phase by coprecipitation method.The precursor is calcined in an inert atmosphere to obtain a ZnO@C nanocomposite catalyst.A series of characterizations of HRTEM,XRD,FTIR,XPS,Raman are carried out.The results are as follow:Salicylate is thermally decomposed into graphitized carbon,and the high-crystallinity and purity Zn0(4-9 nm)nanoparticles are uniformly dispersed in the graphite carbon matrix;the graphite carbon and ZnO form a strong interaction with the C-O-Zn;the graphite carbon surface contains a large number of hydrophilic functional groups(-OH).By controlling the calcination temperature,we can control the structure and composition of ZnO@C nanocatalyst.The catalyst exhibited excellent catalytic activity for visible light degradation of methylene blue,and the degradation rate of methylene blue reached more than 80%within 5 hours,which is superior to commercial ZnO and P25.The catalyst has excellent stability and still maintains high catalytic activity after being recycled for 4 times.2.The binary layered hydroxide zinc-nickel was prepared by modifying the metal composition of the precursor layer.In the absence of reducing agent,Ni-ZnO@C nanocomposite catalyst is prepared by one-step calcination.XRD,HRTEM,Raman,FTIR and XPS characterization results as follows:In the pyrolysis process,no NiO is formed,the nickel ions are reduced to Ni,and the strong chemical is formed between Ni and the graphite carbon by C-O-Ni bond;graphite carbon surface contains a large number of hydrophilic hydroxyl groups.The performance of the catalyst for photodegradation of methylene blue is investigated.The catalytic rate of Ni-ZnO@C was 1.11 times that of ZnO@C.Further photocurrent test shows that the modification of Ni accelerates the electron transport rate of the composite system,so it has more excellent catalytic activity.The catalyst is reused 4 times,and the degradation rate of the contaminant methylene blue is above 90%,indicating that the catalyst has good stability.3.In the absence of template and additional carbon source,a novel Metal-free porous carbon nanocatalyst is prepared in one step by calcining layered zinc hydroxide intercalated with salicylate at 900?.A series of characterization results as follow:No Zn element is detected in the carbon nanocatalyst obtained by pyrolysis of salicylate.The catalyst is rich in pore structure and reduced oxygen functional group(-OH)and has a large specific surface area(2480 m2/g).Catalytic activity of the catalyst is investigated by catalytic reduction of p-nitrophenol(4-NP).The degradation of 4-NP is completed in 4 min,which is superior to commercial Pb/C and Pt/C catalysts.In addition,the catalyst has a wide pH(5-11)range of application and still exhibits good catalytic activity at lower NaBH4 concentrations.