Merlin

The morphologies and size of as-synthesized samples were characterized by high-performance field emission SEM (Zeiss Merlin) and TEM (JEOL JEM 2010F), and the elemental contents were assessed using EDS. The XRD data were performed on an X-ray diffractometer (Rigaku D/max-B, Japan) with Cu-K_a radiation (λ = 0.154056 nm) between 5° and 90° in 2θ. Raman spectra were collected on a LabRAM HR Evolution spectrometer between 1,000 and 3,000 cm⁻¹. XPS were captured in an ESCALAB 250 X-ray photoelectron spectrometer (Thermo Fisher Scientific, USA) with monochromatic 150W Al-Kα radiation. FTIR spectra were obtained by using a Netzsch X70 FTIR spectrometer between 500 and 4,000 cm⁻¹. The pore diameters and specific surface were obtained from the results of the N₂-physisorption surface area and porosity analyser (Quantachrome, USA) at 77 K using the Barrett–Joyner–Halenda (BJH) and BET calculations, respectively. UV–VIS absorbance spectra were captured in a spectrophotometer (HACH 6000). The isotope-labeled catalysts were analyzed in a ¹H-NMR spectrometer (800-MHz, Bruker). ⁵⁷Fe Mössbauer spectroscopy data were recorded on a Rh/⁵⁷Co source using an Fe foil for velocity calibration.