Abstract
Quantum dot (QD) sensitization can increase the light absorption and electronic transmission of photocatalysts. However, limited studies have been conducted on the photocatalytic activity of photocatalysts after modification by noble metal QDs. In this study, we developed a simple method for fabricating Pd-QD-modified g-C3N4. Results showed that the modification of Pd-QDs can improve the NO photocatalytic oxidation activity of g-C3N4. Moreover, Pd-QD modification changed the NO oxidation mechanism from the synergistic action of h+ and O2− to the single action of ·OH. We found that the main reason for the mechanism change was that Pd-QD modification changed the molecular oxygen activation pathway from single-electron reduction to two-electron reduction. This study can not only develop a novel strategy for modifying Pd-QDs on the surface of photocatalysts, but also provides insight into the relationship between Pd-QD modification and the NO photocatalytic oxidation activity of semiconductor photocatalysts.
Highlights
The strongest peak at 27.41, which corresponded to 0.326 nm, was due to the stacking of the conjugated aromatic system that was indexed as the (002) peak for graphitic materials
No other peaks, such as Pd, could be detected in the X-ray diffraction (XRD) pattern of palladium QDs (PQDs)-g-C3 N4, which indicates that the content of deposited
We found that the only ·OH− was generated on PQDs-g-C3N4
Summary
Since Fujishima and Honda discovered oxygen and hydrogen evolution at a semiconductor electrode under light irradiation in 1972 [1], semiconductor photocatalysis have attracted worldwide attention in the fields of water or air purification [2,3,4,5], water splitting [6] and CO2 photoreduction [7,8]. Many researchers turn to develop new photocatalysts that are active under visible light Among these endeavors, Wang et al [13] reported that graphitic carbon nitride (g-C3 N4 ) can produce oxygen or hydrogen by water splitting under visible light irradiation. To increase the efficiency of this attractive material, many methods, such as surface area enhancement, anionic or cationic doping and coupling with other semiconductors, have been developed by researchers [18,19,20] Despite all of these properties, the visible light photocatalytic activity of g-C3 N4 is still low because of the fast recombination of the photogenerated carriers. The reasons for the enhancement of the photocatalytic activity were analyzed in detail
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