Deadline for manuscript submissions: 31 December 2024.
Bi4V2O11 possesses a bandgap of ~1.9 eV, and the band positions of minimum conduction band and maximum valence band straddle the redox potentials of H+/H2 and O2/H2O. In the current work, photoanode made of particulate Bi4V2O11 film displays a wide range of light adsorption. However, when the anode was fabricated by drop-casting and examined for photoelectrochemical water splitting, the photocurrent density of the pristine Bi4V2O11 was low. Improvement has then been carried out by Mo-doping. The Mo-doped Bi4V2O11 photoanode achieves a maximum photocurrent density of 0.3 mA/cm2 after a post deposition necking treatment to improve the connectivity of the drop-cast particles in the film. This material also shows a stability with maintaining 80% photocurrent after 2 h test. Discussion has been made on the displayed performance in PEC water splitting of the Bi4V2O11 materials. Potential solutions have been proposed for this type of promising photoanode material for water splitting.
Photocatalytic synthesis of hydrogen peroxide (H2O2) can be an environmentally friendly and energy-saving solution. However, the oxygen reduction reaction (ORR) rate is limited due to the low solubility of O2 in water. In this study, a modified BiVO4 (BVO) photoanode combined with an Sn-coordinated phthalocyanine gas diffusion electrode (SnPc-GDE) was employed for the synthesis of H2O2, and the oxy-gen reduction reaction rate was increased through a unique three-phase interface system. When visible light was irradiated on the BVO photoanode, the hole-electron pairs were excited and the oxygen evolution reaction (OER) was driven through the holes, and the excited electrons were transferred to the SnPc-GDE to reduce O2 for the synthesis of H2O2. Oxygen vacancy enrichment on the BVO electrode was achieved by photoetching and annealing under an N2 atmosphere, which effectively improved the carrier separation efficiency. Complexation with a WO3 layer formed a built-in electric field, which further promoted the electron-hole pair separation. The SnPc catalyst-modified GDE electrode has the best selectivity for ORR and remains stable during long-term reactions. Under bias-free conditions, the generation rate of H2O2 reached 952.5 μM·L−1·h−1, with a Faradaic efficiency of 48.4%. This study provided a practical strategy for designing a highly efficient BVO/SnPc-GDE photoelectrochemical system to produce H2O2 based on improvement in electron-hole transmission efficiency and product selectivity.
Photocatalytic (PCO) and photothermocatalytic oxidation (PTCO) of ethene (C2H4) and ethanol (EtOH) are investigated using TiO2 and 1%Pt/TiO2 coating on velvet glass support in the presence of UV-A and UV-C irradiation. Both VOC are efficiently mineralised under UV-A irradiation and PCO, but the presence of Pt has a minor impact on their transformation. Instead, there is only a slight increase in the disappearance of EtOH and the formation of acetaldehyde, which are already observed in the dark. Surprisingly, when a higher photon flux is emitted with a UV-C lamp, photocatalytic disappearance and mineralisation of EtOH are less effective than under UV-A irradiation in the presence or absence of Pt. Similar behaviour is also observed on C2H4 PCO in the presence of 1%Pt/TiO2 but not on its PCO mineralisation with TiO2, which is improved by a factor equivalent to the number of photons emitted. Under PTCO, by increasing the temperature from 40 °C to 120 °C, only a benefit impact is observed on C2H4 and EtOH disappearance but an important decrease of mineralization of C2H4 was observed in presence of TiO2 and UV-C The behaviour of these two VOCs under different irradiations and temperatures will be discussed according to the catalytic process.
