Stepwise structural evolution toward robust carboranealkynyl-protected copper nanocluster catalysts for nitrate electroreduction.

Atomically precise metal nanoclusters (NCs) are emerging as idealized model catalysts for imprecise metal nanoparticles to unveil their structure-activity relationship. However, the directional synthesis of robust metal NCs with accessible catalytic active sites remains a great challenge. In this work, we achieved bulky carboranealkynyl-protected copper NCs, the monomer Cu13·3PF6 and nido-carboranealkynyl bridged dimer Cu26·4PF6, with fair stability as well as accessible open metal sites step by step through external ligand shell modification and metal-core evolution. Both Cu13·3PF6 and Cu26·4PF6 demonstrate remarkable catalytic activity and selectivity in electrocatalytic nitrate (NO3-) reduction to NH3 reaction, with the dimer Cu26·4PF6 displaying superior performance. The mechanism of this catalytic reaction was elucidated through theoretical computations in conjunction with in situ FTIR spectra. This study not only provides strategies for accessing desired copper NC catalysts but also establishes a platform to uncover the structure-activity relationship of copper NCs.

Interfacial Properties and Hopping Diffusion of Small Nanoparticle in Polymer/Nanoparticle Composite with Attractive Interaction on Side Group.

The diffusion dynamics of fullerene (C 60 ) in unentangled linear atactic polystyrene (PS) and polypropylene (PP) melts and the structure and dynamic properties of polymers in interface area are investigated by performing all-atom molecular dynamics simulations. The comparison of the results in two systems emphasises the influence of local interactions exerted by polymer side group on the diffusion dynamics of the nanoparticle. In the normal diffusive regime at long time scales, the displacement distribution function (DDF) follows a Gaussian distribution in PP system, indicating a normal diffusion of C 60 . However, we observe multiple peaks in the DDF curve for C 60 diffusing in PS melt, which indicates a diffusion mechanism of hopping of C 60 . The attractive interaction between C 60 and phenyl ring side groups are found to be responsible for the observed hopping diffusion. In addition, we find that the C 60 is dynamically coupled with a subsection of a tetramer on PS chain, which has a similar size with C 60 . The phenyl ring on PS chain backbone tends to have a parallel configuration in the vicinity of C 60 surface, therefore neighbouring phenyl rings can form chelation effect on the C 60 surface. Consequently, the rotational dynamics of phenyl ring and the translational diffusion of styrene monomers are found to be slowed down in this interface area. We hope our results can be helpful for understanding of the influence of the local interactions on the nanoparticle diffusion dynamics and interfacial properties in polymer/nanoparticle composites.