A quaternary ammonium cyclodextrin polymer for efficient photocatalytic production of hydrogen peroxide from pure water

A photocatalytic system can be used to efficiently produce hydrogen peroxide (H2O2) without introducing a sacrificial agent or oxygen (O2). This system has practical application potential but remains challenging to implement. To increase the H2O2 yield of this system, a quaternary ammonium cyclodextrin polymeric photocatalyst QCD36A1-1350 is successfully synthesized using quaternization modification and low-temperature polycondensation. The photocatalyst is used to produce H2O2 from pure water and air by the one-step two electron oxygen reduction reaction. Under irradiation by visible light, QCD36A1-1350 produces a higher H2O2 yield (of up to 2.51 mmol g−1h−1) than unquaternized polymers and reported metal-free catalysts under similar conditions. Experimental and theoretical studies clearly show that the introduction of quaternary ammonium groups can effectively broaden the visible light absorption of polymer catalysts, while increasing the hydrophilicity, charge transfer efficiency and surface stability. The practicability of efficient photocatalytic production of H2O2 is realized by increasing the activity and selectivity of the polymer photocatalyst.