Humidity-Independent Photocatalytic Toluene Mineralization Benefits from the Utilization of Edge Hydroxyls in Layered Double Hydroxides (LDHs): A Combined Operando and Theoretical Investigation

Abstract

Water vapor (humidity) has been known as one of the important enhancement factors in the photocatalytic degradation of volatile organic compounds (VOCs). In this study, a composite structure of TiO2/Mg–Al layered double hydroxides (LDHs) has been constructed, which displays unique humidity-independent photocatalytic activity. Optimized structure has shown toluene degradation efficiency values as high as 74.3% under a completely dry atmosphere and the degradation efficiency ranges between 73.2% to 84.3% as the humidity increases from 0 to 90%. The origin of humidity-independent photocatalytic activity is investigated by in situ attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy, which can distinguish H2O and hydroxyl via different adsorption modes. We found that the OH– would lose electrons and be oxidized into hydroxyl radicals at the edge of LDH to participate in toluene mineralization reaction under light irradiation. The surface structure of the sample can be recovered when the surface hydroxyl is consumed, because of the existence of water vapor. Density functional theory (DFT) theoretical calculations verify that H2O molecules are more likely to dissociate and adsorb through the isolated hydrogen-terminated hydroxyl group (OHT) on LDH surface to generate hydroxyl radicals to participate in toluene photocatalytic degradation under harsh conditions, compared with the case on TiO2 surface. This work introduces a new strategy to promote the efficiency of the photocatalytic degradation of VOCs under a wide range of relative humidity.

Insights into Dynamic Surface Bromide Sites in Bi4O5Br2 for Sustainable N2 Photofixation

“…To conduct rapid scan FT‐IR, typically, a drop of water was placed on the sample to offer an aqueous reaction environment as shown in Figure S8a. Both BOB and BrV‐BOB in water are observed to have an IR absorption peak near 1640 cm −1 of H 2 O bending for H 2 O adsorption (Figure S8b, c) [17b] …”

Aqueous Photocatalytic Recycling of Gold and Palladium from Waste Electronics and Catalysts

“…It has been proven through capture experiments that photogenerated electron–holes and oxygen radicals are the key active substances in the dissolution reaction (Figure a). Electrons and holes are generated under the action of photocatalysis (Supporting Information Figure S12). , Oxygen free radicals are mainly composed of superoxide free radicals ( • O 2 – ) and hydroxyl free radicals ( • OH), which are the reaction products of oxygen and electrons or water and holes, respectively. The equation is as follows …”

Chemical Discrimination of Benzene Series and Molecular Recognition of the Sensing Process over Ti-Doped Co3O4

“…In Figure 6a, the broad IR peak at 3100−3600 cm −1 could be assigned to the stretching vibration of the −OH group. 41 The sharp IR peak located at 3068 cm −1 could be identified as the unsaturated CH bond stretching vibration. In Figure 6b, the IR peaks at 1596, 1519, and 1448 cm −1 were identified as the characteristic stretching vibration of the benzene skeleton.…”