Late-model g-CNQDs/H3PW12O40/TiO2 heterojunction nanocatalyst with enhanced photocatalytic performance

Abstract

The g-CNQDs/H3PW12O40/TiO2 heterojunction photocatalytic material is fabricated by facile ultrasonic method. The crystal structure, elemental composition, morphology and optical properties of as-synthesized catalysts are investigated by a series of characterizations. Studies have shown that g-CNQDs have been successfully doped into H3PW12O40/TiO2. The introduced g-CNQDs are uniform in size and have an average diameter of 5.8 nm. The 5% g-CNQDs/H3PW12O40/TiO2 shows the highest degradation efficiency of 99.3% toward RhB under simulated sunlight for 30 min, which is 5.68 times than of H3PW12O40/TiO2 under same conditions. The improved photocatalytic activity of the g-CNQDs/H3PW12O40/TiO2 ternary system is attributed to the expansion of visible-light absorption region and diminishing photoelectron–hole recombination. The testing of radical scavengers demonstrated that the main active species in the photocatalytic process involving three active species are ·O2− and ·OH, and the holes (hVB+ ) play an auxiliary role. The photodegradation efficiency of g-CNQDs/H3PW12O40/TiO2 ternary composite catalyst is reduced by 6.2% after five cycling runs. The present work proposes an efficient optimization of the fabrication of potent and stable TiO2-based photocatalysts driven by sunlight.