Executive Summary : | The project aims to resolve the existing the gap in catalyst characterization between experiments and density functional theory (DFT) based electronic structure calculations, through a proposed scanning transmission electron-microscopy (STEM) based method of 3D characterization from 2D images. The symmetry-broken noble metal nanostructures, target materials of this proposal, will be synthesized wet-chemically, and will be interrogated through aberration-corrected STEM. The atomic models will be built from quantitative STEM data based atom-counting and will be fed into DFT simulations for selective dynamics to compute ‘real’ structures obtained in the experiments. This has the potential to emerge as an alternate method to conventional electron tomographic characterization for monoatomic nanomaterials in 3D at atomic-resolution. Once the image simulation of the computed structure under imaging conditions matches the real image, i.e. the real structure is found out, the oxygen binding onto the structures will be carried out in DFT. Also, the shifts in d-band centre will be compared to that of conventionally modelled surfaces, to pinpoint the importance of the experimental data. Furthermore, the oxygen reduction mechanism will be carried out through nudged elastic band (NEB) calculations to explore the two well-established mechanisms, i.e. four or two electron pathways and corresponding electrochemical experiments will be carried out to look at the mechanistic details of the reaction. Overall, the proposed research aims to interrogate the structure of the wet-chemically synthesized symmetry-broken nanostructures at atomic-scale to establish structural and electronic descriptors for their activity in electrochemical oxygen reduction reaction. |