Z-scheme TiO2/g-C3N4 composites with improved solar-driven photocatalytic performance deriving from remarkably efficient separation of photo-generated charge pairs

• There exists a strong interaction between TiO2 and g-C3N4.
• The photo-induced charge separation rate has been greatly enhanced.
• The photocatalytic activity has been remarkably promoted.
• The composites follow a typical Z charge separation and migration mechanism.

High recombination rate of electron-hole pairs and weak oxidation ability of holes from g-C3N4 greatly limit the catalytic degradation efficiency of g-C3N4-based photocatalysts, thus it is crucial to further improve the photocatalytic efficiency of g-C3N4. In this paper, TiO2 was successfully loaded onto the g-C3N4 surface to induce the electron−hole separation and enhance the photocatalytic efficiency. The results revealed the maximum photocatalytic performance toward discoloration of methyl orange (MO) aqueous solution under the simulated sunlight illumination at molar ratio of 3% TiO2 to g-C3N4 composite. The junction between TiO2 and g-C3N4 significantly accelerate the separation of the photo-generated charge pairs caused by the strong interactions between TiO2 and g-C3N4. Such highly efficient photo-generated charge separation can be explained by a Z-scheme charge separation and migration mechanism based on the results of the scavenger experiments and the energy band structures.

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