Transmission electron microscopy (TEM) measurement was performed using a JEOL-JEM 2100 system equipped with an EDX detector. To prepare a TEM sample, the sample powder was put into ethanol and sonicated to obtain the suspension, which was subsequently dropped onto the copper grid. STEM-EDS measurements were carried out on a Thermo Fisher Scientific Talos F200C instrument equipped with Bruker Xflash 6T-30 EDS detector, High angle angular dark field detector (HAADF) for STEM imaging and a Thermo Fisher Scientific Ceta 16megapixel CMOS camera. Powders were dispersed in cyclohexane, and 4 μL was deposited on a gold grid covered by QuantiFoil® holey carbon, filtered and then dried in air.