Quinone Carbonyl‐Functionalized Carbon Dots Enable Selective 2e − Oxygen Reduction for Benzyl Alcohol‐Assisted Photocatalytic H 2 O 2 Production

Photocatalytic hydrogen peroxide (H 2 O 2 ) production through the two‐electron oxygen reduction reaction (2e − ORR) is often limited by competing four‐electron reduction. Here, a precursor‐controlled series of carbon dots (CDs) is developed. The quinone‐associated carbonyl characteristics are systematically tuned by varying the resorcinol‐to‐catechol feed ratio. Across this chemically related series, spectroscopic and electrochemical changes in quinone‐associated surface chemistry correlate with photocatalytic H 2 O 2 production, with resorcinol‐derived CDs ( m ‐CDs) showing the highest activity. In a benzyl alcohol (BA)/ H 2 O biphasic system, BA serves as the reductive substrate, coupling its oxidation with O 2 reduction to H 2 O 2 . A plate‐type microchannel reactor delivers H 2 O 2 production rates of 17.71 and 54.19 mmol g −1 h −1 at 25 and 60°C, respectively, under 450 nm irradiation. In situ spectroscopy and electron paramagnetic resonance (EPR) show reversible light‐induced changes in carbonyl/oxygen‐containing surface states, and EPR features consistent with semiquinone‐type and ∙ OOH‐related species. Combined with the electrochemical and photocatalytic results, these observations support peroxide‐selective O 2 reduction and motivate a proposed quinone‐associated surface redox model that may involve proton and electron transfer. This work establishes a tunable CDs platform for probing and regulating quinone‐associated surface chemistry in photocatalytic H 2 O 2 production.