N-doped carbon dots decorated 3D g-C3N4 for visible-light driven peroxydisulfate activation: Insights of non-radical route induced by Na+ doping

A novel material with N-doped carbon dots decorated three-dimensional graphitic carbon nitride (NCDs/TCN) is synthesized using NaCl as template. Abundant Na+ are found to be in-situ doped in 3D g-C3N4 framework. Experiments and density functional theory (DFT) calculations suggest that peroxydisulfate (PDS) activation follows radical and non-radical pathways on the NCDs/TCN catalyst. NCDs have superior up-conversion photoluminescence property and can enhance charge separation efficiency, thus improving the photocatalytic reactivity of 3D g-C3N4 and promoting the radical activation of PDS efficiently. Interestingly, the NCDs/TCN-PDS* complex can be formed due to the large adsorption energy of doped Na+ for PDS, thus inducing the non-radical PDS activation pathway. This work provides an effective approach to combine radical and non-radical pathways for boosting PDS activation and gives deep insights for the non-radical pathway induced by doped Na+ in 3D g-C3N4.