Kinetics insights into size effects of carbon nanotubes'growth and their supported platinum catalysts for 4,6-dinitroresorcinol hydrogenation

Size effects are a well-documented phenomenon in heterogeneous catalysis,typically attributed to alterations in geometric and electronic properties.In this study,we investigate the influence of catalyst size in the preparation of carbon nanotube(CNT)and the hydrogenation of 4,6-dinitroresorcinol(DNR)using Fe_(2)O_(3)and Pt catalysts,respectively.Various Fe_(2)O_(3)/Al_(2)O_(3)catalysts were synthesized for CNT growth through catalytic chemical vapor deposition.Our findings reveal a significant influence of Fe_(2)O_(3)nanoparticle size on the structure and yield of CNT.Specifically,CNT produced with Fe_(2)O_(3)/Al_(2)O_(3)containing 28%(mass)Fe loading exhibits abundant surface defects,an increased area for metal-particle immobilization,and a high carbon yield.This makes it a promising candidate for DNR hydrogenation.Utilizing this catalyst support,we further investigate the size effects of Pt nanoparticles on DNR hydrogenation.Larger Pt catalysts demonstrate a preference for 4,6-diaminoresorcinol generation at(100)sites,whereas smaller Pt catalysts are more susceptible to electronic properties.The kinetics insights obtained from this study have the potential to pave the way for the development of more efficient catalysts for both CNT synthesis and DNR hydrogenation.

Towards a molecular understanding of the electronic metal-support interaction(EMSI)in heterogeneous catalysis

Tailoring the electronic metal-support interaction(EMSI)has attracted considerable interests as one of the most efficient approaches to improve both the activity and stability of metal catalysts in heterogeneous catalysis.In this viewpoint,we illustrate the methodology and relevant fundamentals on the disentanglement,characterization,and interpretation of EMSI.Under the choice of monometallic catalyst over inert support,a combination of optimal experiment design,multimodal techniques,in situ characterization,with a comprehensive understanding of the underlying measurement protocols is highly desirable for a reliable determination of EMSI.Accordingly,not only the d-band filling but also d-band energy within the EMSI should be taken into consideration for providing general principles to guide the electron-promoting catalytic reaction.

Kinetics and mechanistic insights into the active sites of Au catalysts for selective propylene oxidation

Identification of the catalytically active sites emerges as the prerequisite for an atomic-level comprehensive understanding and further rational design of highly efficient catalysts.Here,we demonstrate a kinetics strategy to identify the active sites of Au catalyst for the disentanglement of geometric and electronic effects on the selective oxidation of propylene to acrolein.Both the Ti-containing titanium-silicalite-1(TS-1)and Ti-free silicalite-1(S-1)were employed as supports to immobilize Au catalysts,which were investigated by a combination of multiple characterization,kinetics analysis,crystal structure modelling.The Au(111)sites are identified as the main active site for acrolein formation,while their electronic effects are highly relevant to the presence or absence of Ti.Moreover,propylene epoxide(PO)formation mainly involves the co-participation of Au and Ti sites,the proximity between Au and Ti sites is found to have less influences on PO formation in a certain distance.In comparison,acrolein is very likely to generate over Au(111)sites via the hydrogen-assisted O_(2) activation to oxygenated species for its oxidizing propylene.The insights gained here could guide the design and preparation of Au catalysts for selective propylene oxidation.