Deadline for manuscript submissions: 30 June 2025.
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.
The degradation of metformin hydrochloride (MET) and glibenclamide (GLI), widely used anti-diabetics, was performed using an electrochemical advanced oxidation process, namely electro-Fenton, and several other Advanced Oxidation Processes (AOPs) of photocatalytic nature, like UV/H2O2, UV/persulfate, and UV/TiO2. The electrochemical behavior of the drugs was first characterized by cyclic and differential pulse voltammetry. The data implied that both drugs present quasi-reversible oxidation. The effect of the applied current and the airflow in the electrogeneration of hydrogen peroxide was studied. Degradations of 60% of the initial drug were obtained for aqueous solutions of 30 mg·L−1 of MET and 15 mg·L−1 of GLI by using photoelectron-Fenton conditions with 1.0 A of current and a Fe2+ concentration of 3.5 mg·L−1, although the removal of MET required 60 min of reaction while for GLI only 45 min were needed. The mineralization (organic carbon removal) percentages after 60 min of treatment were 20%and 30% for electro-Fenton and photo electro-Fenton processes, respectively. For UV/H2O2, UV/persulfate, and UV/TiO2 treatments of MET solutions, the order of observed degradations was UV/PS > UV/H2O2 > UV/TiO2 with maximum values of drug removal of 30% after 60 min of irradiation. This efficiency is lower than the removal observed with the electro-Fenton reaction. For GLI the order of degradation efficiency was UV/PS > UV/TiO2 > UV/H2O2, with maximum values of drug removals of 99.5% after only 10 min of irradiation. This performance is clearly better that in the case of electro-Fenton or photo-electro-Fenton. The removals of the two drugs when dissolved in chemical matrices that mimic real hospital wastewaters and seawater were also studied. They showed a clear dependency on the pharmaceutical of choice. While the degradation of MET was hampered by the presence of other chemicals in the two water matrices, GLI removal was remarkable, pointing towards a possible application in real wastewaters.
The study explored the use of 3D-printed plastics as catalyst supports for gas-phase photocatalytic applications. Specifically, it compared three commonly used plastic materials: PLA, ABS, and PETG. The process involved 3D modeling, additive manufacturing through 3D printing, and functionalization via dip-coating with titanium dioxide (TiO2). The study evaluated the loading capacity of the materials, the adhesion of the films, and the optical properties of the photocatalytic plates. Finally, the three plastic samples were tested as support materials in a laboratory-scale flat-plate reactor for the photocatalytic oxidation of dichloromethane in air. Loading capacities of around 3 mg/cm2 for TiO2 were achieved, along with radiation absorption capacities close to 65%. A correlation between loading and absorption fraction was identified, leading to the proposal of a simple saturation model; in turn, it allowed the predictive model of pollutant conversion as a function of the absorbed fraction of radiation. By analyzing both qualitative and quantitative properties and results, in order to determine the most suitable plastic material to be used in a photocatalytic wall reactor, PLA emerged as the best choice among the materials tested. These results show promise for the effective utilization of these plastics in the design of air decontamination devices.