Efficient photocatalytic production of hydrogen peroxide using dispersible and photoactive porous polymers

Abstract

Developing efficient artificial photocatalysts for the biomimetic photocatalytic production of molecular materials, including medicines and clean energy carriers, remains a fundamentally and technologically essential challenge. Hydrogen peroxide is widely used in chemical synthesis, medical disinfection, and clean energy. However, the current industrial production, predominantly by anthraquinone oxidation, suffers from hefty energy penalties and toxic byproducts. Herein, we report the efficient photocatalytic production of hydrogen peroxide by protonation-induced dispersible porous polymers with good charge-carrier transport properties. Significant photocatalytic hydrogen peroxide generation occurs under ambient conditions at an unprecedented rate of 23.7 mmol g^-1 h^-1 and an apparent quantum efficiency of 11.3% at 450 nm. Combined simulations and spectroscopies indicate that sub-picosecond ultrafast electron "localization" from both free carriers and exciton states at the catalytic reaction centers underlie the remarkable photocatalytic performance of the dispersible porous polymers.

Fig. 1. Synthesis and solution processing of the CTPs.

a Synthesis of TT–CTP and TTH–CTP. b Photos of TTH–CTP dispersed in various solvents under natural light and laser irradiation, showing the Tyndall effect.

Fig. 2. Photocatalytic production of H₂O₂.

a Time-dependent production rate of H₂O₂ on TT–CTP and TTH–CTP in pure water. b H₂O₂ generation rates of photocatalytic half-reaction of TT–CTP and TTH–CTP with and without benzyl alcohol as a hole sacrificial agent. c UV–Vis spectra and AQY of H₂O₂ generation for TT–CTP and TTH–CTP. d H₂O₂ generation rates and AQY of different photocatalysts. The red star represents TTH–CTP in this work (with benzyl alcohol, see panel b) and the orange, green, sky-blue, and blue circles correspond to other previously reported photocatalysts. e H₂O₂ generation rates of photocatalytic half-reaction of TT–CTP and TTH–CTP under different pH values. f H₂O₂ generation rates of photocatalytic half-reaction of TTH–CTP under different cycles.

Fig. 3. Theoretical calculations.

a TD-DFT-calculated absorption spectra and oscillator strengths for the model system of TT–CTP at the O₂-adsorbed state. The insets are the transition orbits at the maximum oscillator strength. b TD-DFT-calculated absorption spectra and oscillator strengths for the model system of TTH–CTP at the O₂-adsorbed state. The insets are the transition orbits at the maximum oscillator strength. c Calculated free energy diagrams of H₂O₂ production catalyzed by TT–CTP model system. The state of “abs_O₂” denotes the O₂-adsorbed state, and the states of “act_1”, “act_2”, and “act_3” represent three evolutionary steps to activate the O₂ molecule. d Calculated free energy diagrams of H₂O₂ production catalyzed by TTH–CTP model system. The state of “abs_O₂” denotes the O₂-adsorbed state, and the states of “act_1”, “act_2”, and “act_3” represent three evolutionary steps to activate the O₂ molecule. C: gray; N: blue; H: white; O: red; S: yellow.

Fig. 4. Charge-carrier dynamics of the CTPs.

a Temperature-dependent integrated photoluminescence intensity of TT–CTP. The red line is the fitting curve according to the Arrhenius equation. The inset shows the temperature-dependent photoluminescence spectra. b Temperature-dependent integrated photoluminescence intensity of TTH–CTP. The blue line is the fitting curve according to the Arrhenius equation. The inset shows the temperature-dependent photoluminescence spectra. c Terahertz photoconductivity dynamics of TT–CTP and TTH–CTP thin films. The samples were photoexcited by a 400-nm femtosecond pump pulse with an incident pump fluence of 886 μJ cm⁻² in a dry N₂ environment. d TA spectra for TT–CTP thin film upon excitation at 500 nm. e TA spectra for TTH–CTP thin film upon excitation at 500 nm. f Comparison of the 660-nm kinetic curve in TT–CTP thin film and the 680-nm kinetic curve in TTH–CTP thin film.