Hrtem

The crystalline phase and structure of PdO–NiO, NiO and PdO were obtained from X-ray diffractometer (Bruker AXS company, Germany). Functional groups and metal oxide peaks of the catalysts was analyzed by ATR-FTIR (iS5, Thermo Scientific, USA). Morphology images and elemental composition of metal oxides were monitored by (FE-SEM) Hitachi S-4800 II (Japan). The HR-X-ray &UV Photoelectron Spectrometer (XPS, Thermo scientific, USA) was used to analyze the metal bonding. High resolution images and mapping images of the catalyst are analyzed from HR-TEM (Hitachi) instrument. The PL excitation and emission spectra were obtained by using HORIBA Fluoromax spectrofluorometer. The catalytic reduction of nitrophenol and dye molecules were systematically studied by using UV–Vis spectrophotometer (Shimadzu).

TEM analysis was done using high-resolution transmission electron microscopy (HR-TEM) (Hitachi, Clarksburg, MD, USA). For the analysis, one drop of the diluted sample was placed on a 200 mesh Cu grid coated with a layer of carbon 20 ± 5 µm in thickness. The dried sample was placed into a JEOL double tilt specimen holder and inserted into a JEOL 2100-F TEM operating at 200 kV. The sample was allowed to stabilize at a column pressure of 9.0 × 10⁻⁶ Pa in the microscope before imaging. The absence of formvar as a grid support increases the transmission of the electron beam. Therefore, a condenser lens aperture with a diameter of 50 µm was chosen to reduce unnecessary electron interaction with the sample, employing an emission current of 119 µA. The microscope was aligned by performing JEOL’s standard alignment procedures, followed by high-resolution alignment. The images were collected using a GATAN camera (Gatan Inc., Pleasanton, CA, USA) and processed with GATAN digital micrograph software (Gatan Microscopy Suite 3, Pleasanton, CA, USA).