Solar-to-hydrogen peroxide energy conversion on resorcinol–formaldehyde resin photocatalysts prepared by acid-catalysed polycondensation

Abstract

The photocatalytic generation of hydrogen peroxide from water and dioxygen (H2O + 1/2O2 → H2O2, ΔG° = +117 kJ mol–1) under sunlight is a promising strategy for the artificial photosynthesis of a liquid fuel. We had previously found that resorcinol–formaldehyde (RF) resin powders prepared by the base-catalysed high-temperature hydrothermal method act as semiconductor photocatalysts for H2O2 generation. Herein, we report that RF resins prepared by the acid-catalysed high-temperature hydrothermal method (~523 K) using common acids at pH < 4 exhibit enhanced photocatalytic activity. The base- and acid-catalysed methods both produce methylene- and methine-bridged resins consisting of π-conjugated and π-stacked benzenoid–quinoid donor–acceptor resorcinol units. The acidic conditions result in the resins with a lower bandgap (1.7 eV) and higher conductivity because the lower-degree of crosslinking creates a strongly π-stacked architecture. The irradiation of the RF-acid resins with simulated sunlight in water with atmospheric-pressure O2 generates H2O2 at a solar-to-chemical conversion efficiency of 0.7%, which is the highest efficiency ever reported for powder catalysts used in artificial photosynthesis.

High Performance Generation of H2O2under Piezophototronic Effect with Multi‐Layer In2S3Nanosheets Modified by Spherical ZnS and BaTiO3Nanopiezoelectrics

“…Most importantly, the generation rate of H 2 O 2 on ZnS/In 2 S 3 /BTO increases continuously during 5 h of piezophotoreaction, and the concentration of H 2 O 2 formed reaches approximately 1160 µ m even after the sixth cycle reaction (Figure 4e,f). Obviously, this yield of H 2 O 2 with ZnS/In 2 S 3 /BTO in piezophotocatalysis is comparable to that of excellent photocatalysts and piezoelectric semiconductors, such as resorcinol‐formaldehyde resins [ 30 ] and melon‐based C 3 N 4 photocatalysts, [ 13b ] as is summarized in Table S1, Supporting Information. Furthermore, the morphology of ZnS/In 2 S 3 /BTO remains the same before reaction and after six consecutive uses (see Figure S16a,b, Supporting Information).…”

Nanospatial Charge Modulation of Monodispersed Polymeric Microsphere Photocatalysts for Exceptional Hydrogen Peroxide Production

“…The structure of the polymer is verified by powder XRD (Figure S16, Supporting Information). All of the mesoporous resin sphere materials investigated exhibited broad diffraction at 2θ = ≈ 20° (d = ≈ 4.4 Å), assigned to (002) planes of graphitic carbon, indicative of a narrowed distance between the aromatic planes (π-stacking) and stronger interactions of D-A couples [39] (Figure S17, Supporting Information). This three-dimensional cross-linked structure facilitates the charge transfer (CT) transition of D-A couples that enhances light capture.…”

Hybrid Proton-Exchange Membrane Based on Perfluorosulfonated Polymers and Resorcinol–Formaldehyde Hydrogel

“…The absorption increased with the F exposure time and implicitly with RF gel concentration in the membrane. The RF gel resulting from the polycondensation reaction provided the absorption band at 540 nm, related to the charge transfer transitions of the π-conjugated and π-stacked donor–acceptor units [ 41 ]. The absorption band at 270 nm appeared due to an aromatic ring in pure resorcinol present in the membrane, while the broad band at 440 nm was specific to the dimerization of resorcinol [ 42 ].…”