Jem 2100

The as-prepared products were characterized on an XRD (Bruker-D8 advance) equipped with a Cu Kα radiation source (λ = 1.5418 Å) at a scanning rate of 6 ° min⁻¹; X-ray tube voltage and current were set at 40 kV and 40 mA, respectively. SEM, TEM, and HAADF-STEM images were taken with an FEI Nova NanoSEM NPE218, JEM-2100, and JEM-ARM200F, respectively. The samples were prepared by dropping ethanol dispersion of samples onto carbon-coated copper TEM grids using pipettes and dried under ambient condition. EELs were recorded using an FEI Talos F200X equipped with super-EDX and energy filter (Gatan GIF Quantum ER 965) operated at 200 kV under STEM mode. By using Gatan Quantum 965 with dual EELs capability, both low- and high-loss region were collected near simultaneously, which allows accurate measurement of chemical shifts as EELs SI analysis was carried out. XPS was performed on an AXIS ULTRA DLD X-ray photoelectron spectrometer. UV-Vis absorption spectrum was obtained from Lambda 750S (Perkin Elmer, Inc., USA). Elemental content was tested by EDX and ICP-optical emission spectroscopy (iCAP7600). Raman spectra were recorded by a DXR Raman spectrophotometer (Thermo Fisher Scientific) at an excitation radiation wavelength of 532 nm.

The Bruker D8 Advance was used to acquire room-temperature powder XRD data, while the crystal structure of the electrode material was investigated by high-temperature XRD using a Rigaku D/max 2500 V high-temperature accessory. Raman spectrometer (Seki Technotron model STR 750 with 514.5 nm argon laser) has been used for deducing the vibrational modes of the powder samples. The SEM (JEOL-S4800) was employed to obtain the surface morphology of both powders and cells. Powder elemental distribution and microstructure were obtained by HR-TEM (JEOL, JEM-2100) and TEM-EDX (FEI Tecnai G2 T20). Elemental valence states were explored by XPS (Thermo ESCALAB 250). The mass changes of the sample during the warming process were detected using TGA (Model STA 449 F3, NETZSCH). O₂/H₂O-TPD were acquired by a mass spectrometer (MS, Hiden, HPR20), and H₂O-TPD data were acquired after the powders were pretreated in moist air at 600 °C for 10 h. The material’s specific surface area was determined using the Quanta chrome AutoSorb-iQ3 instrument through nitrogen adsorption-desorption isotherms. Dense bars were used to test TEC data in air atmosphere by means of Netzsch 402 C/3/G. Co K-edge and Fe K-edge XANES were performed at NSRRC in Taiwan. The photon energies of Co K-edge and Fe K-edge spectra were calibrated using metallic Co and Fe foils as references, respectively.

TEM (JEOL, JEM-2100) and HRTEM (FEI, Tecnai G2 F30 S-Twin TEM) were measured for imaging. The phase composition was measured by the Bruker D8 ADVANCE X-ray diffractometer (XRD). BET-specific surface areas and pore structures were determined by a Beishide 3H-2000PS2 system. XPS measurement was performed on a Thermo Scientific ESCALAB 250Xi spectrometer. The photocurrent response experiment was performed on a photoelectrochemical workstation (CIMPS-2, Zahner) with a three-electrode system; 300 W Xe lamp and Na₂SO₄ aqueous solution (0.1 M) were used as the light source and electrolyte solution, respectively. The hydroxyl radicals were detected using a fluorescence spectrophotometer (Hitachi F-7000).

PXRD data were collected at room temperature using a Rigaku Ultima diffractometer using Cu Kα radiation. The diffractometer was operated at 40 kV and 40 mA, with a scan rate of 5° min⁻¹ and a step size of 0.02°. TEM images were recorded on a JEOL JEM-2100 or FEI Tecnai F20 microscope at an acceleration voltage of 200 kV. SEM measurements were performed on a Hitachi S-4800 microscope operated at 5 kV. UV-visible absorption spectra were collected using a spectrophotometer (TU-1900, Beijing Purkinje General Instrument Co. Ltd, China). Nitrogen adsorption–desorption isotherms were measured at 77 K using a Quantachrome Autosorb-IQ-2C-TCD-VP analyzer and were used to calculate the surface areas of the nanozymes with the BET method. The temperature-dependent magnetization was measured on a MPMS SQUID magnetometer (MPMS-3, Quantum Design) with a magnetic field of H = 1 kOe under field-cooling procedures. O K-edge X-ray absorption spectroscopy (XAS) measurements were performed at the beamline BL12B-a (CMD) in Hefei Synchrotron Radiation Facility, National Synchrotron Radiation Laboratory.

Transmission electron microscopy was carried out on JEOL JEM 2100 and Cs-TEM FEI Titan G2. X-ray powder diffraction (XRD) patterns were recorded on an X-ray diffractometer (Rigaku D/max 2500) with Cu Kα radiation (40 kV, 30 mA, λ = 1.5418 Å) at a scan rate of 10° min⁻¹ in the 2θ range from 8 to 60°. X-ray photoelectron spectra (XPS) were carried out by using a model of ESCALAB 250. ICP-MS measurement (Thermo X Series II ICP/MS quadrupole system, Thermo Fisher Scientific) was employed to investigate the chemical composition of Ru/CoFe-LDHs and the metal dissolution amounts in the electrolytes for different electrocatalysts during stability test. Calibration ranges from 0.01 to 100 ppb yielding a linear response in the range of 100–10,000,000 counts. The detection limit (DL) was 0.005 ppb.

Powder XRD patterns of the dried samples were recorded on Bruker D8 diffractometer at a scanning rate of 2° min⁻¹ using Cu Kα radiation (λ = 1.5406 Å). XPS and UPS spectra were recorded on the ESCALAB 250Xi (Thermo Fisher Scientific) system. The XPS results were calibrated with the reference C 1s peak located at 284.6 eV. The X-ray absorption fine structure (XAFS) experiments under transmission mode were performed at the 7-BM of the National Synchrotron Light Source II (NSLS-II) which is using a channel-cut monochromator. The NSLS-II is rung at 400 mA electron beam current under top-off mode. Samples for SEM and TEM characterizations were prepared by dropping nanomaterial dispersions in toluene on a silicon substrate and amorphous carbon-coated copper grid, respectively. SEM images were obtained using FESEM, JEOL JSM-7800F. TEM characterization was performed with a JEOL JEM-2100 and FEI TF20 operated at 200 kV. Dark-field STEM, Cs-HAADF STEM, and elemental mapping images were obtained using FEI Titan G2 60-300 operated at 300 kV as well as a JEM-ARM200F operated at 200 kV. The 3D reconstruction of Ag-CdS icosapods was carried out using FEI Titan G2 60-300 operated at 60 kV.