2.2 Characterization of samples
The morphologies of the samples were measured by field emission scanning
electron microscope (SEM: JSM-6701F. JEOL) and transmission electron
microscope (TEM: FEI Tecnai TF 20). The crystalline structure was
analyzed by X-ray diffraction (XRD: Rigaku RINT-2000) patterns, all
samples were scanned from 5° to 80° at a scanning rate of 5°/min under
40 mA and 40 kV. The chemical composition and valence state of the
catalyst were detected by X-ray photoelectron (XPS: ESCALAB 250Xi).
UV-vis diffuse reflectance spectra (DRS) were performed by Shimadzu UV
2550 spectrophotometer with BaSO4 powder was used as a
reference. Photoluminescence (PL) spectra and time resolved
photoluminescence (TRPL) spectra were analyzed on a FlUOROMAX-4
spectrophotometer (HORIBA Scientific, France) with the excitation
wavelength of 390 nm. Brunauer–Emmett–Teller (BET) surface area and
N2 adsorption-desorption isotherms were carried out on
an ASAP2020M instrument at 77 K.
The electrochemical tests and photoelectrochemical properties of MCS,
NiSe2 and MCNS-10 samples were performed by an
electrochemical workstation (VersaSTA4-400, AMETEK). The transparent
solution of Na2SO4 (0.2 M) was used as
electrolyte. In this test system, a platinum sheet was used as the
counter electrode and reference electrode of saturated calomel electrode
(SCE) and the work electrode of as-prepared was the fluorine-doped tin
oxide (FTO) coated. The FTO working electrodes was prepared as follows:
the FTO glass were cut to 2×1 cm2, it was orderly
washed with acetone, ethanol and deionized water in ultrasonic devices.
5 mg catalyst was ultrasonically dispersion for 1 h in 100 μL anhydrous
ethanol containing 10 μL of 5% Nafion solution. Then the dispersed
solutions of catalyst was uniformly coated FTO glass with the areas
about 1 cm2 until it dried. The linear sweep
voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were
measured at room temperature with a scan rate of 0.05 V
s−1. When the forward bias is 0.2 V, the EIS of
samples were measured in a frequency range of 1MHz to 1 Hz at AC
amplitude of 10 mV. Mott-Schottky was tested under the frequency of 1000
Hz.