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Heterojunction Photocatalysts: Boon for Water Purification
Published in A. Pandikumar, K. Jothivenkatachalam, S. Moscow, Heterojunction Photocatalytic Materials, 2022
Ariharaputhiran Anitha, Amalraj John
accumulated on SC B, redox reaction occurs on the SC with lower redox potential. Moreover, the electron–hole pairs cannot be effectively separated. These two factors reduce the redox ability of the heterojunction photocatalyst.
Electrical Properties of Metals and Semiconductors
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
The voltage developed in a solar cell depends on the incident light intensity and can be derived as follows. In the absence of sunlight, the current-voltage relationship of a solar cell is the same as a standard pn junction as shown in Equation (3.16). When light with energy greater than the bandgap of the semiconductor falls on the solar cell, electron-hole pairs are created, then separate under the electric field at the pn junction to produce a current. Therefore, an additional term must be added to Equation (3.16) as follows: I(V)=Io[exp(eVkT)−1]−αG
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
What happens when a semiconductor material is heated or when we shine light on the semiconductor? Conductivities of semiconductors are altered by the action of heat or light. Heat or light energies break the chemical bonds, leading to the formation of electron–hole pairs. These electron–hole pairs participate in electrical conduction, increasing the conductivity of the material.
CdIn2S4-based advanced composite materials: Structure, properties, and applications in environment and energy – A concise review
Published in Inorganic and Nano-Metal Chemistry, 2023
Gaurav Yadav, Md. Ahmaruzzaman
Photocatalysis has been considered an advances technique which was significant in progress in recent years.[9,10] Photocatalysts provide green and clean energy without generating any harmful products.[11] In the past, titanium oxide was thought to be one of the most effective photocatalysts due to its non-toxicity, high stability, high activity, and low cost.[12,13] Photocatalysts gained a lot of attention due to coupling.[11] Semiconductor photocatalyst coupled with other materials enhance properties such as charge carrier separation, light harvesting, and bandgap energy. The obtained photocatalyst possesses high accessibility to catalytic sites and large active centers.[14] Photocatalysis is an important area of research because it seeks to find economically viable solutions to the world’s environmental and energy crises. Several different steps are involved in photocatalysis: (i) absorbing light to generate electron-hole pairs, (ii) separating excited charges, (iii) bringing electrons and holes to the surface, (iv) recombining electron-hole pairs, and (v) using surface charges in redox reactions.[15]
Island detection methods and grid current control methods in SPV-based energy systems
Published in International Journal of Ambient Energy, 2022
The movement of the electrons is described as follows: (1) absorption of a photon leads to the generation of an electron–hole pair. (2) Usually, the electrons and holes will recombine. (3) With impermeable membranes, the electrons and the holes can be separated. (4) The separated electrons can be used to drive an electric circuit. (5) After the electrons pass through the circuit, they will recombine with holes, maintaining the integrity of specifications. When the light falls on the p-n junction, the light photons can easily enter into the junction through the very thin p-type layer. The solar energy, in the form of photons, gives sufficient energy to the junction and excites the valance band electrons to the conduction band, thereby creating a number of electron–hole pairs. The free electrons in the depletion region will move to the n-type side of the junction because of the electric field across the junction. Similarly, the holes in the depletion move to the p-type side of the junction. Once, the newly created free electron–holes move to the p-type and the n-type material, higher the concentration of electrons in one side i.e. n-type side of the junction and higher the concentration of holes in another side i.e. the p-type side of the junction, the p-n junction will behave like a small battery cell. Due to this separation of charge on either side, voltage is set up, which is known as photo voltage. If we connect a load across this junction, there will be current flowing through it (Anudeep and Nayak 2017).
An overview: recent development of semiconductor/graphene nanocomposites for photodegradation of phenol and phenolic compounds in aqueous solution
Published in Journal of Asian Ceramic Societies, 2021
Reyhaneh Kaveh, Hassan Alijani
The absorption of photons to generate electron/hole pairs is the key to an effective photocatalytic reaction. Lots of semiconductors have wide band gaps, so they can be excited under UV illumination. Since the visible light accounts for 46% and UV light only accounts for 5% of the total energy from the sun, it is perfect to utilize visible solar energy because of the large amount that reaches the Earth’s surface [53]. Another profound issue that must be considered is the recombination rate of electron/hole pairs. This factor has significant effect on the photocatalytic performance of semiconductors. It is very necessary to decrease the recombination rate of electron/hole pairs. Moreover, heterogenous photocatalysis also requests for the adsorption of the contaminants on the surface of photocatalyst as an essential step. Consequently, appropriate concentrating the target contaminants around the surface of semiconductor can be highly efficient in improving the photocatalytic reaction due to the contaminants can then react readily with •OH radicals, and also serve as scavengers for electrons and holes [54,55].