Atomic Structure of 2 nm Size Metallic Cobalt Prepared by Electrochemical Conversion: An in Situ Pair Distribution Function Study

Abstract

Conversion reactions, offering high capacity in batteries, imply a restructuration of the pristine atomic structure down to the nanoscale. The associated large broadening in the Bragg peaks of restructured electrode renders the description of atomic structure, almost impossible using conventional x-ray diffraction. On the other hand, atomic pair distribution function is well suited to probe the structure of few nanometer size particles. Here, we investigated the formation mechanism and structure of 2-nm particle size of metallic Co obtained by electrochemical conversion of CoF2. We found that the conversion process stabilized a disordered structure consisting of an hcp-fcc intergrowth. The reaction was followed by in-situ PDF providing unique insight into the growth of highly defective Co nanoparticles.

Comprehensive study of a versatile polyol synthesis approach for cathode materials for Li-ion batteries

“…This discrepancy suggest the presence of disorder (e.g. stacking faults) in the hcp-like phase which is likely related to the hcp-fcc intergrowth phenomena previously observed in nanosized Co metal [58,59].…”

There's no place like real-space: elucidating size-dependent atomic structure of nanomaterials using pair distribution function analysis

“…Since then, several PDF and total scattering studies have focused on the structures of non-fcc and hcp structures in metallic nanoparticles. 117,123,124 Vargas et al used PDF and TEM to characterize the atomic structure in long and ultrathin Au nanowires. In this study, many possible structural models in 2 nm by 12 nm nanowires were generated and energetically optimized using Molecular Dynamics simulations.…”

“…74,245 The interest and development of advanced computational techniques such as database mining and machine learning are very likely to impact PDF analysis as well as many other dataheavy elds in the coming years. 246 For example, machine learning methods have already been applied to PDF in regards to component analysis 123,[247][248][249][250] and in identifying symmetry and extracting distance lists. 251,252 This development is likely to aid in maximizing the information that can be extracted from the PDF of complicated nanostructures.…”

Cobalt‐Catalyzed Dehydrogenative Coupling of Amines into Imines

“…The crystalline nature of the particles was confirmed by X‐ray diffraction (XRD) which uncovered broad peaks at 44.4° and 51.8° most likely corresponding to the (111) and (200) planes of the face‐centered cubic (fcc) phase of cobalt . The fcc crystal structure is presumably formed due to the small size of the nanoparticles which is also the reason for the broadening of the signals. The presence and distribution of cobalt in the particles was also confirmed by elemental mapping with energy disperse X‐ray spectroscopy (EDS).…”