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Fundamentals of Water Electrolysis
Published in Lei Zhang, Hongbin Zhao, David P. Wilkinson, Xueliang Sun, Jiujun Zhang, Electrochemical Water Electrolysis, 2020
Xiaoxia Yan, Rida Javed, Yanmei Gong, Daixin Ye, Hongbin Zhao
Among them, photodissociation of water to produce hydrogen is through the absorption of solar energy by photocatalyst powder or electrode to produce photocarriers, which then decompose water into hydrogen and oxygen. Hydrogen production by the splitting of water provides a possible way to directly convert solar energy into clean and storage chemical energy. The design and selection of the reaction system is one of the core issues of realizing efficient photocatalytic hydrogen production and whether it can be industrialized. There are three major types of solar hydrogen production systems29: (1) heterogeneous photocatalytic systems, (2) photoelectrochemical systems (PEC), and (3) photovoltaic-photoelectrochemical hybrid systems (PV-PEC), as shown in Figure 1.2. Different systems have their own advantages, disadvantages, and application scope. Among them, a PV-PEC (photovoltaic)-coupled photochemical conversion system is expected to provide an important development path for the industrialization of hydrogen production by the photodissociation of water.30
Air pollution impacts on ozone
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
In Chapter 1 we looked at two types of photochemical processes – photosynthesis and photosensitisation (Section 1.5.5). Photodissociation (also known as photolysis and photodecomposition), is another photochemical process occurring in both the troposphere and stratosphere whereby a single molecule or compound splits into two or more smaller products (which may be capable of recombining to form the reactants). It forms the basis of the theory for the origin of the ozone layer, originally proposed by the British scientist Sidney Chapman in 1930 (hence known as the Chapman mechanism). It laid the foundation for our understanding of modern stratospheric chemistry. Chapman proposed that the ozone layer originated from the photodissociation of atmospheric O2. He highlighted that the bond energy of the O2 molecule (498 kJ mol−1) is equivalent to the energy of a 240 nm UV photon; hence only photons of wavelengths <240 nm can photolyse the O2 molecule. These high energy photons are present at high altitude above the Earth’s surface.
Laser Ionization Techniques
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
The bond breaking and making of typical bimolecular reactions becomes simplified in so-called half-collision processes—the molecular photodissociation process is often referred to like this, since it involves the breaking of a molecular bond only. In this context, REMPI probing has proven to be a versatile tool for investigating the quantum-state distribution of photodissociation fragments.
Molecular photodissociation in the vacuum ultraviolet region: implications for astrochemistry and planetary atmospheric chemistry
Published in Molecular Physics, 2021
Despite the technical challenge discussed above, there are still many research topics involving molecular photodissociation that can be done within the reach of the current experimental developments, and are highly needed by the fields of astrochemistry and planetary atmospheric chemistry. This article will highlight two of these researches that are currently in progress in several laboratories worldwide.