Electrocatalytic water splitting using organic polymer materials-based hybrid catalysts
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Introduction Current environmental and energy issues are increasingly and more urgently calling for clean and renewable energy source alternatives. Because the oceans account for 71% of the earth’s area, the use of water to produce H2 and O2 can sustainably and efficiently provide support for hydrogen applications and provide further solutions to energy shortages and environmental problems.1 There are two classes of efficient electrocatalysts to achieve full splitting of water at low overpotential: hydrogen production at the cathode (HER) and oxygen production at the anode (OER). OER is a four-proton-coupling reaction, while HER is a two-electron-transfer reaction. The corresponding reaction equations for HER and OER are listed below as Equation 1 and Equation 2, respectively. It can be seen that OER requires higher reaction energy, namely overpotential, to overcome the kinetic barrier. Therefore, the ability of electrocatalytic water splitting can be improved mainly by improving OER reactivity. 2 H + + 2e− → H 2
(1)
2 H 2O → O2 + 4 H + + 4e−.
(2)
Currently, the noble metal platinum (Pt) is the most common HER-active metal, and the noble metal oxide (IrOx or RuOx) is the benchmark for electrocatalytic OER. However, an increasing number of researchers have been devoted to finding substitutes, since precious metals including Pt are scarce and expensive. Transition metals are gaining much attention as alternatives to precious metals because they have vacant d orbitals, which can act as electrophiles in chemical reactions, or they can provide lone pairs of electrons to act as nucleophiles, to form intermediates that reduce the activation energy and facilitate the reaction. So far, a variety of compounds have been studied as catalysts for water splitting, including sulfides,2,3 nitrides, carbides4,5 and carbon materials,6,7 clusters,8 and single atoms.9,10 Organic species used for inorganic chemical reactions, especially electrocatalysis, must have good conductivity. Many polymers meet these requirements. Organic polymers have received widespread attention due to their unique properties, tunable chemical and band structure, easy processability, and chemical and thermal stability.11,12 In this article, we summarize three categories of organic polymers:
Lijuan Niu, Beijing University of Technology, China; [email protected] Lu Sun, Beijing University of Technology, China; [email protected] Li An, Beijing University of Technology, China; [email protected] Dan Qu, Beijing University of Technology, China; [email protected] Xiayan Wang, Beijing University of Technology, China; [email protected] Zaicheng Sun, Beijing University of Technology, China; [email protected] doi:10.1557/mrs.2020.167
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• VOLUME 45 • JULY 2020 Auckland • mrs.org/bulletin © 2020 Materials Research Downloaded MRS fromBULLETIN https://www.cambridge.org/core. University of Technology, on 14 Jul 2020 at 03:06:05, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/mrs.2020
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