Selectivity Control of CO₂ Reduction over Pt/g-C₃N₄ Photocatalysts under Visible Light

Photocatalysts based on g-C3N4 have been investigated in the CO2 reduction reaction under visible light irradiation (lambda = 397, 427, 452 nm). Photocatalysts were prepared by melamine calcination at 500-600 degrees C with further platinum deposition (0.1-1.0 wt.%). The effect of the preparation conditions of g-C3N4 and the method of platinum deposition on the physicochemical properties and activity of photocatalysts was studied. The photocatalysts were investigated by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, X-ray diffraction, high resolution transmission electron microscopy, UV-Vis spectroscopy, and low temperature nitrogen adsorption techniques. It has been found that the efficiency of CO2 reduction is governed by the surface area of g-C3N4 and the presence of platinum in the metallic state, while the optimal content of platinum is 0.5 wt. %. The highest rate of CO2 reduction achieved over Pt/g-C3N4 photocatalyst is 13.2 mu mol h(-1) g(-1) (397 nm), which exceeds the activity of pristine g-C3N4 by 7 times. The most active photocatalysts was prepared by calcining melamine in air at 600 degrees C, followed by modification with platinum (0.5 wt.%).