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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
Hydrogen Production from Biomass
Published in Vladimir Strezov, Hossain M. Anawar, Renewable Energy Systems from Biomass, 2018
The technologies with the highest energy efficiency are fossil fuel (mainly natural gas) reforming (83%), plasma arc decomposition (70%), biomass gasification (65%), and coal gasification (63%). Biofuel reforming and other biological alternatives (e.g., dark fermentation, biophotolysis, and photofermentation) are currently not showing the advantage in energy efficiency. Photochemical-based methods, such as photocatalysis, photoelectrochemistry, artificial photosynthesis, and photoelectrolysis, are the least efficient, with energy efficiency values below 10%.
Magnetoelectrochemistry and Photoelectrochemistry of Porous Materials
Published in Antonio Doménech-Carbó, Electrochemistry of Porous Materials, 2021
The term photoelectrochemistry is in general applied to all phenomena where photon absorption is accompanied by electrochemical processes. The usual requirements for photoelectrochemical activity are: (a) the semiconductor character of the electrode material, (b) the existence of an electrolyte concentration high enough to significantly exceed the density of charge carriers in the semiconductor, and (c) the semiconductor should be reverse biased with respect to the solution [16].
Modeling and Simulation of Radioactive Nanomaterials of Pb-U, Pb-Th, and Pb-Co in Water-Filled Containers for Nuclear Security Applications
Published in Nuclear Science and Engineering, 2022
Elham Gharibshahi, Miltos Alamaniotis
One of the most fascinating and functional aspects of nanomaterials is their optical properties.16 In this regard, the optical properties of nanoparticles are highly attractive for scientists to do research in nanomaterials and physical chemistry due to their surface plasmon resonance characteristics and strong extinction efficiency in the visible spectrum.17,18 However, the optical properties of nuclear nanoparticles intended both experimentally and theoretically have not been studied very sufficiently.19,20 Applications based on the optical properties of nanoparticles comprise optical detector, sensor, laser, imaging, phosphor, solar cell, display, photocatalysis, photoelectrochemistry, and biomedicine.16
Transition-metal-free electrochemical-induced active C(sp3)-H functionalization
Published in Green Chemistry Letters and Reviews, 2023
Xiaolong Ma, Jinfeng Wei, Xu Yang, Huajin Xu, Yi Hu
Under the background of the traditional energy shortage crisis and increasing awareness of environmental protection, researchers are dedicated to developing environment-friendly and sustainable methods (1–3). The transition-metal-catalyzed C–H bond functionalization (4–11) realizes the precise cleavage of the C–H bond and the construction of C–X (X = C, N, O, S, etc.) by non-directed strategies(for example high reactive C–H bond) (12, 13) or directed strategies (introducing directed groups(DGs)) (7, 14, 15) or transient directed groups(TDGs) (16, 17) in cooperation with adding appropriate ligands (18–20) which greatly improves the reaction efficiency and selectivity. However, this method still has many disadvantages, such as using expensive, polluting, and unrecycled transition metal catalysts and requiring high reaction temperature, etc. In recent years, photochemistry (21–25), electrochemistry (26–29), and photoelectrochemistry (PEC) (30–34) have been extensively used for C–H bond functionalization and have brought about great breakthroughs. As we all know, electrochemistry has always been considered as a green, powerful, sustainable tool in organic synthesis. It acts as a redox agent by adjusting the current or voltage to replace the traditional redox agents which could not meet the economic standards. In addition, electrochemistry also provides a number of other advantages despite the fact that the limitations of substrates are still relatively large, such as completing difficult reactions in fewer steps, using durable and recyclable electrode materials, and reducing the waste of reaction reagents. Compared to transition-metal-catalyzed C–H bond functionalization, electrochemistry provides an alternative mechanism for C–H bond functionalization (35). The electrochemical mechanism can be roughly divided into two categories, one is direct electrolytic oxidation (Scheme 1A), and the other is indirect electrolytic oxidation (Scheme 1B). In Scheme 1A, the reactions proceed via electron transfer (ET) from the organic molecule to the anode, enabling self-oxidation of single substrates or oxidative coupling of different substrates. In Scheme 1B, such methods employ a medium called electrocatalyst, which transfers electrons on the electrode and then facilitates the oxidation of substrates in the solution. The reaction can significantly reduce the overpotential through the electrocatalyst to bypass high-energy radical-cation intermediates, to significantly expand the functional group tolerance and comprehensive utility of the reaction. Additionally, because C(sp3)-H (PKa > 50) exists higher bond energy than C(sp2)-H (PKa = 15∼50), it is more difficult to implement C(sp3)-H functionalization, resulting in far fewer reports about C(sp3)-H functionalization than C(sp2)-H functionalization. To my best knowledge, there are few reviews on electrochemical-induced C(sp3)-H functionalization. This review summarizes transition-metal-free electrochemical-induced C(sp3)-H functionalization reactions from 2016 to now.