Abstract
In this work, the lacunary Keggin-type phosphotungstates of [PW9O34]9- (PW9) clusters were loaded onto the g-C3N4 nanosheets (NSs) to synthesize the phosphotungstate clusters-decorated 2D heterojunction photocatalysts by using the electrostatic-force driven self-assembly process. The surface charge polarity of g-C3N4 NSs was changed from a negative to a positive charge through the acidizing treatment. The positively-charged g-C3N4 NSs allowed the negatively-charged PW9 clusters to be adsorbed and deposited onto the g-C3N4 NSs, forming the PW9/g-C3N4 heterojunction NSs. The as-synthesized samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and UV-VIS absorption spectra, respectively. The photocatalytic activity tests indicated that, upon simulated sunlight irradiation, the photocatalytic H2-generation rate of PW9/g-C3N4 heterojunction NSs (~23.8 μmol h−1) was ~3.3 times higher than that of the pure g-C3N4 NSs (~7.3 μmol h−1). The enhanced photocatalytic activity of PW9 cluster-decorated g-C3N4 NSs could be attributed to the enhanced separation process of the photoinduced charge-carriers, due to the Z-scheme-mediate charge transfer behavior across their hetero-interface.
Highlights
The continuous burning of unsustainable fossil energy sources, which emits large amounts of harmful gases, has induced a global energy crisis and environmental contamination
To synthesize the PW9 /graphite C3 N4 (g-C3 N4) heterojunction NSs, the g-C3 N4 bulk was crushed into the g-C3 N4 nanosheets (NSs), at first, through the ultrasonic method
The positively-charged g-C3 N4 NSs were suspended into the water solution of PW9 to enable the negatively-charged PW9 to be self-assembled onto the g-C3 N4 NSs, based on the electrostatic force [22,23]
Summary
The continuous burning of unsustainable fossil energy sources, which emits large amounts of harmful gases, has induced a global energy crisis and environmental contamination. Since the H2 generation from the photo-driven water splitting over the TiO2 semiconductor photocatalyst was first reported in 1972 [5], this photochemical reaction has been widely used in the research area of solar-to-fuels conversion, mainly owing to its low cost and low energy consumption [6,7,8]. Material has attracted increasing interest in the area of photocatalytic H2 generation [11,12] This kind of metal-free semiconductor with a 2D nanosheet structure can open new prospects for the application of solar-to-fuels conversion because it is an abundant, cheap and stable semiconductor, with a suitable energy-level position for reducing protons. It is believed that our work will provide a new platform to construct the ultra-small polyoxometalates cluster-decorated g-C3 N4 NSs for highly-efficient photocatalytic solar-to-fuels conversion
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