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Fundamentals of Semiconductor Photoelectrochemistry
Published in Anirban Das, Gyandshwar Kumar Rao, Kasinath Ojha, Photoelectrochemical Generation of Fuels, 2023
Mamta Devi Sharma, Mrinmoyee Basu
A subfield of physical chemistry is electrochemistry, and photoelectrochemistry is a branch of electrochemistry that deals with the interaction of light and electrochemical systems. Photoelectrochemistry attracted huge attention globally as it can be used to convert the energy of light to electricity. A photoelectrochemical (PEC) process is influenced by light in various ways. An electrochemical cell is composed of electrode and electrolyte, so in a PEC cell photoexcitation may happen in either electrode or electrolyte molecule. After the photoexcitation of the electrode, depending on whether the electrode material is a semiconductor or a metal, different phenomena can take place. When the electrode is a metal, then after photoexcitation by high energy photon (<>work function of the metal) results in photoemission of electrons from the electrode surface. In the case when the electrode is a semiconductor instead of a metal, under certain situations, the semiconductor absorbs the incident photons whose energy is greater than the bandgap of the material. Under such conditions, a PEC cell is developed. Photoexcitation of the electrolyte molecule results in the photogalvanic cell or a dye-sensitized solar cell.1,2
Magnetoelectrochemistry and Photoelectrochemistry of Porous Materials
Published in Antonio Doménech-Carbó, Electrochemistry of Porous Materials, 2021
The operation of dye-sensitized solar cells involves a set of processes initiated by the photoexcitation of the dye. Then, one electron is injected from the excited sensitizer to the semiconductor so that the dye is transformed in its oxidized state. This process competes with the decay of the excited dye to its ground state. The next step is the transport of electrons through the mesoporous semiconducting film. The back-electron transfer reactions involve the electron transfer from the conduction band to the oxidized sensitizer, or the recombination of electrons with any acceptor species in the electrolyte. To operate in a cyclic way, the oxidized dye must be regenerated. This is achieved with an electron acceptor in the electrolyte that captures electrons from the semiconductor, being subsequently reduced at the counter electrode. In the example illustrated in Figure 15.12, iodide ions act as electron acceptors regenerated at the Pt electrode via the I3– + 2e– → 3I– process.
Remediation of Wastewater
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials II, 2021
Shalini Chaturvedi, Pragnesh N. Dave
Interaction of light energy with metallic nanoparticles got attention due to their photocatalytic activities for various pollutants (Akhavan, 2009). These photocatalysts are made of semiconductor metals. It can degrade organic pollutants in wastewater like detergents, dyes, pesticides, and volatile organic compound (Lin et al., 2014). Semiconductor nanocatalysts are effective for the degradation of halogenated and non-halogenated organic compounds for heavy metals (Adeleye et al., 2016). The mechanism of photocatalysis is based on the photoexcitation of electron in the catalyst. The irradiation with light generates holes and exited electrons. In an aqueous medium, water molecules trapped the holes and hydroxyl radicals are generated (Anjum et al., 2016). The radicals act as a powerful oxidization agent. These hydroxyl radicals oxidize the organic pollutants and generate water and gaseous degradation products (Akhavan, 2009). Due to high reactivity under ultraviolet light (k< 390nm) and chemical stability, TiO2 is most applicable in photocatalysis (Akhavan, 2009). ZnO has also been extensively studied by researchers (Lin et al., 2014). Efficiency of photocatalyst depends on the factors like particle size, band gap energy, dose, pollutant concentration, and pH. CdS nanoparticles as a photocatalyst also received attention for the treatment of industrial dyes in wastewater (Tristao et al., 2006; Zhu et al., 2009).
Remediation of water and wastewater by using engineered nanomaterials: A review
Published in Journal of Environmental Science and Health, Part A, 2018
Obadia K. Bishoge, Lingling Zhang, Shaldon L. Suntu, Hui Jin, Abraham A. Zewde, Zhongwei Qi
The mechanism of photocatalysis in a solution is initiated by photoexcitation of the semiconductor along with the formation of an electron–hole pair on the catalyst surface. The potential oxidative hole (h+VB), which is formed in the presence of the catalyst, allows the oxidation of organic matter to react and the formation of very reactive hydroxyl radicals through the dissociation of water.[144] To increase the production of ROS and thus enhance photocatalytic activity, researchers have not only applied surface or structural modification techniques (such as metal ion doping[145,146] and insertion of non-metals[147]) but also combined different physical and chemical treatment processes.[148,149]
Investigation on photocatalytic degradation of crystal violet dye using bismuth ferrite nanoparticles
Published in Journal of Dispersion Science and Technology, 2021
Shahnaz Kossar, I. B. Shameem Banu, Noor Aman, R. Amiruddin
The photoexcitation mechanism generally leads to the existence of electrons in the conduction band with reduction ability and holes in the valence band with the oxidizing ability.[50] During the photocatalysis process, the oxygen (O2) molecules in the air will capture the electrons in the conduction band and result in the formation of superoxide anion () molecules as explained in Equation (5).