Synthesis And Catalytic Properties Of Platinum-based Materials On ZIF-8 Deriverd N-doped Carbon

Platinum,as a member of the noble metal group,is well known as one of the most useful and versatile catalytic materials.Due to its outstanding catalytic performance,platinum are highly demanded in industry.However,the storage of platinum on earth is rather low,limiting its wide commercialization.Therefore,novel catalysts with lower platinum amount and superior catalytic activity are highly desired.In this thesis,single-atom platinum and platinum nanoparticles have been successfully synthesized with the distinct synthetic routes and their catalytic performances have been studied.Zeolitic Imidazolate Framework(ZIF),a subclass of MOF(Metal-Organic Framework),is chosen as a precursor of the carbon support.Firstly platinum single atom material is synthesized by encapsulating metal precursor of Pt(acac)2 in the molecular cages of ZIF-8.After carbonization at 900?under Ar atmosphere,ZIF-8 is transformed to nitrogen-doped carbon and the Pt precursor inside the cages is reduced by the organic linker,leading to the formation of single platinum atoms anchored on N-doped carbon.The oxidation of styrene using TBHP as oxidant is chosen as a probe reaction.The result shows that 0.04Pt/CN exhibited high catalytic activity for styrene oxidation to benzaldehyde with 67.5%conversion and 78.8%selectivity to benzaldehyde after 12h.Secondly,well-dispersed platinum nanoparticles were successfully synthesized through a two-step synthesis involving doping and adsorption approach to enhance the density of the active sites.Pt precurors are firstly confined in the cages of ZIF-8.After carbonization at 900? under Ar atmosphere,the obtained powder was used as a host to adsorb additional Pt and N sources followed by direct pyrolysis at 900?.The product exhibited well-dispersed nanoparticles with size of 20 nm on N-doped carbon which were related to their electrocatalytic activity.Compared to commercial Pt/C and Pt/CN-first which is obtained at the first-step synthesis,Pt/CN-0.2second showed excellent electrocatalytic performance for ORR with half-wave potential of 0.78 V.The Pt/CN-0.2second also exhibited stable electrocatalytic performance for ORR with half-wave potential value decreased 25 mV(0.755 V)after 2000 cycles of stability test.