Transmission Electron Microscopy and elemental mapping: TEM images were collected at The Facility for Electron Microscopy Research (FEMR) of Mcgill University. TEM characterization was performed using Thermo Scientific Talos F200X G2 (S)TEM with High visibility lowbackground beryllium double-tilt optimized for energy-dispersive X-ray spectroscopy (EDS). All samples were prepared by carefully scratching off from the electrode and dispersing them onto ethanol solution. After sonicating for 5 min, the solution was drop cast onto a copper grid supporting a thin electron transparent carbon film. High angular annular dark-field imaging (HAADF) performed in parallel with EDS acquisition in the collection angle of 58-200 mrad.