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Band gap-tunable potassium doped graphitic carbon nitride with enhanced mineralization ability was prepared using dicyandiamide monomer and potassium hydrate as precursors. X-ray diffraction (XRD), N2 adsorption, UV-Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared catalysts. The CB and VB potentials of graphitic carbon nitride could be tuned from -1.09 and +1.56 eV to -0.31 and +2.21 eV by controlling the K concentration. Besides, the addition of potassium inhibited the crystal growth of graphitic carbon nitride, enhanced the surface area and increased the separation rate for photogenerated electrons and holes. The visible-light-driven Rhodamine B (RhB) photodegradation and mineralization performances were significantly improved after potassium doping. A possible influence mechanism of the potassium concentration on the photocatalytic performance was proposed.

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Interstitial P doping is more effective in improving the photocatalytic activity compared with substitutional P doping.

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Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Herein, we report a novel g-C3N4/ZnSnCdS heterojunction photocatalyst prepared using the hydrothermal method that has an outstanding nitrogen photofixation ability under visible light. The as-prepared ZnSnCdS is the ternary metal sulfide Zn0.11Sn0.12Cd0.88S1.12 with many sulfur vacancies, not a mixture of ZnS, SnS2, and CdS. Strong electronic coupling, as evidenced by the ultraviolet–visible, X-ray photoelectron spectroscopy, photoluminescence, and electrochemical impedance spectra results, exists between two components in the g-C3N4/ZnSnCdS heterojunction photocatalysts, leading to more effective separation of photogenerated electron–hole pairs and faster interfacial charge transfer. The sulfur vacancies on ternary metal sulfide not only serve as active sites to adsorb and activate N2 molecules but also promote interfacial charge transfer from ZnSnCdS to N2 molecules, thus significantly improving the nitrogen photofixation ability. With the ZnSnCdS mass percentage of 80%, the as-prepared heterojunction photocatalyst exhibits the highest NH4 + generation rate under visible light, which is 33.2-fold and 1.6-fold greater than those of individual g-C3N4 and ZnSnCdS.

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Nitrogen fixation is the second most important chemical process in nature, next to photosynthesis. Herein, we report a novel g-C3N4/ZnMoCdS heterojunction photocatalyst with outstanding nitrogen photofixation ability under visible light prepared by hydrothermal post-treatment. The as-prepared ZnMoCdS is the ternary metal sulfide Zn(0.12)Mo(0.12)Cd(0.9)S(1.14) with many sulfur vacancies, not a mixture of ZnS, MoS2 and CdS. Strong electronic coupling, as evidenced by the UV-Vis, XPS and EIS results, exists between two components in g-C3N4/ZnMoCdS heterojunction photocatalysts, leading to more effective separation of photogenerated electron-hole pairs and faster interfacial charge transfer. The sulfur vacancies on ternary metal sulfides not only serve as active sites to adsorb and activate N2 molecules but also promote interfacial charge transfer from the catalyst to N2 molecules, thus significantly improving their nitrogen photofixation ability. With an optimal ZnMoCdS mass percentage of 80%, the as-prepared heterojunction photocatalyst exhibits the highest NH4(+) generation rate under visible light, which is 13.5-fold and 1.75-fold greater than those of individual g-C3N4 and ZnMoCdS, respectively.