Rational design and observation of the tight interface between graphene and ligand protected nanocrystals

Imaging the kinetics of anisotropic dissolution of bimetallic core-shell nanocubes using graphene liquid cells

Chemical design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics. Here, we apply single-particle imaging coupled with atomistic simulation to study reaction pathways and rates of Pd@Au and Cu@Au core-shell nanocubes undergoing oxidative dissolution. Quantitative analysis of etching kinetics using in situ transmission electron microscopy (TEM) imaging reveals that the dissolution mechanism changes from predominantly edge-selective to layer-by-layer removal of Au atoms as the reaction progresses. Dissolution of the Au shell slows down when both metals are exposed, which we attribute to galvanic corrosion protection. Morphological transformations are determined by intrinsic anisotropy due to coordination-number-dependent atom removal rates and extrinsic anisotropy induced by the graphene window. Our work demonstrates that bimetallic core-shell nanocrystals are excellent probes for the local physicochemical conditions inside TEM liquid cells. Furthermore, single-particle TEM imaging and atomistic simulation of reaction trajectories can inform future design strategies for compositionally and architecturally sophisticated nanocrystals.

Rational design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics. Here, the authors apply single-particle liquid-cell electron microscopy imaging coupled with atomistic simulations to understand pathways and rates of bimetallic core-shell nanocubes undergoing oxidative dissolution.

Integrating Polar and Conductive Fe2O3-Fe3C Interface with Rapid Polysulfide Diffusion and Conversion for High-Performance Lithium-Sulfur Batteries

A low-cost in situ formed Fe₂O₃-Fe₃C heterostructure highly dispersed in carbon nanofiber was delicately designed via a facile one-pot electrospinning method. The intense anchoring (by Fe₂O₃) and rapid electron transfer (by Fe₃C) for lithium polysulfides transformation can be simultaneously achieved on the Fe₂O₃-Fe₃C heterostructure interface, thus preventing the amassment of lithium polysulfides benefiting from its excellent interfacial contact and improving sulfur utilization. Experimental characterizations and DFT calculations confirmed the restrained polysulfides shuttle and enhanced redox kinetics. Therefore, the battery containing optimal Fe₂O₃-Fe₃C heterostructure delivered a high capacity of 776.2 mA h g^-1 after 300 cycles at 1 C at a low fading rate of 0.037% per cycle. Even at a high sulfur loading of 3.5 and 4.5 mg cm^-2, high capacities of 773.6 and 533.6 mA h g^-1 at 0.5 C can be achieved with capacity retentions of 91.7 and 94.2%, respectively. This distinctive heterostructure proposes an effective design of high-performance lithium-sulfur batteries contributing to the excellent electrochemical performance, which can synergize the virtues of effectively adsorptive metal oxides and appealing conductive metal carbides.