Carbon quantum dots as efficient cocatalysts in Fenton-like processes: Preparation optimization and mechanistic...

Carbon quantum dots (CQDs) are promising cocatalysts in Fenton-like technologies, leveraging hydrogen peroxide and boosting Fe^2 + generation and thereby expediting the advanced oxidation process. Although several studies have shown that the preparation affects the cocatalytic performance of the resulting CQDs, the precise correlation between the preparation and the cocatalytic efficiency is unclear. Here, we combine the batch experiments with the theoretical calculations to systematically explore how the parameters in electrochemical exfoliation preparation affect the cocatalytic performance of the as-prepared CQDs. The results show that adjusting parameters like voltage, electrolyte concentration, and electrolysis duration can precisely regulate the surface functional groups of CQDs, which in turn affects the cocatalytic performance. A linear positive correlation is identified between the surface carboxyl content and the pseudo-first-order rate constant (k_obs) in Fenton-like reactions, with the highest carboxyl content (18.26 mmol/g) found in C@C3-30V-24H that induces the optimum catalytic performance to the C@C3-30V-24H-Fe³⁺/H₂O₂ system for phenol removal (97.75 % versus 21.17 % in Fe³⁺/H₂O₂ system at pH 3). DFT calculations reveal that phenolic compounds with electron-donating groups are more readily oxidized and that those with lower LUMO levels demonstrate higher k_obs. This study underscores the crucial role of CQDs preparation on their cocatalytic performance in Fenton-like reactions.