研究目的
To confirm whether introducing Zn into g-C3N4 leads to an increased generation of charge carriers and to clarify the chemical status of the Zn species (doped or deposited on the surface).
研究成果
Loading Zn into g-C3N4 via a one-pot solid-state method significantly enhances photocatalytic H2 evolution under visible light, with an optimum at 0.2 atomic% Zn, achieving a rate of 26.3 μmol/g·h. The improvement is attributed to an increased population of photoexcited electrons, as confirmed by light-induced IR absorption, rather than changes in light absorption or physical properties. The Zn species are present as ZnOx clusters in the +2 oxidation state, coordinated to O atoms, and not doped into the framework. Future studies should focus on understanding the electron population dynamics and optimizing Zn loading for broader applications.
研究不足
The study is limited to Zn loading on g-C3N4 and does not explore other metals or co-catalysts. The mechanism behind the non-linear relationship between Zn concentration and activity is not fully understood, and the interaction between ZnOx clusters and g-C3N4 requires further investigation. The experiments were conducted under specific conditions (e.g., visible light, no co-catalysts), which may not represent all practical applications.
1：Experimental Design and Method Selection:
A one-pot solid-state route was used to load Zn into g-C3N4, with characterization techniques including XRD, FESEM/EDS, TEM, DRS, N2 adsorption-desorption, ICP-OES, XPS, XANES, and light-induced IR absorption to analyze the materials and their photocatalytic properties.
2：Sample Selection and Data Sources:
Samples were prepared with varying Zn atomic percentages (
3：1%, 2%, 4%) using urea and zinc acetate dihydrate as precursors. List of Experimental Equipment and Materials:
Equipment included XRD (Bruker D8-Advance), FESEM/EDS (JSM-7610 F, Jeol), TEM (JEM 2010, Jeol), DRS (Lambda 950, Perkin Elmer), N2 adsorption-desorption apparatus (ASAP 2020, Micromeritics), ICP-OES (ICPS-8100, Shimadzu), XPS (Thermo Scientific), XANES at Synchrotron Light Research Institute, FT/IR spectrometer (FT/IR610, Jasco), Hg-Xe lamp, Xenon lamp with cutoff filter, gas chromatograph (Shimadzu GC-8 A). Materials included urea, zinc acetate dihydrate, methanol, water, CaF2 plates.
4：Experimental Procedures and Operational Workflow:
Photocatalysts were prepared by suspending urea in Zn(Ac)2 solution, drying at 70°C for 5h, calcining at 500°C for 5h in air, washing with water, and drying. Photocatalytic H2 evolution was evaluated in a Pyrex flask with a 300W Xenon lamp (λ > 420 nm), photocatalyst suspended in water-methanol mixture, N2 bubbling to remove O2, and H2 quantified by GC. Light-induced IR absorption measurements were done under vacuum with UV-vis light irradiation.
5：Data Analysis Methods:
Data were analyzed using integrated peak areas from XPS and ICP-OES, absorption spectra from DRS and IR, and kinetic data from H2 evolution experiments.
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X-ray diffractometer
D8-Advance
Bruker
Characterization of crystallographic phases of photocatalyst samples
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Field emission scanning electron microscope
JSM-7610 F
Jeol
Morphology analysis and elemental mapping via energy dispersive X-ray spectroscopy
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Transmission electron microscope
JEM 2010
Jeol
High-resolution imaging to observe nanostructures and clusters
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Diffuse reflectance spectrophotometer
Lambda 950
Perkin Elmer
Measurement of light absorption properties
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Inductively coupled plasma optical emission spectroscopy
ICPS-8100
Shimadzu
Quantification of elemental composition, specifically Zn content
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Fourier transform spectrometer
FT/IR610
Jasco
Recording light-induced infrared absorption spectra to quantify photoexcited electrons
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Gas chromatograph
GC-8 A
Shimadzu
Analysis of evolved hydrogen gas during photocatalytic reactions
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N2 adsorption-desorption apparatus
ASAP 2020
Micromeritics
Determination of surface area and pore characteristics
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X-ray photoelectron spectrometer
Thermo Scientific
Analysis of chemical states and surface composition
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Xenon lamp
300 W
Light source for photocatalytic activity evaluation with cutoff filter for visible light
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Hg-Xe lamp
Light source for light-induced IR absorption measurements
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