Oxygen Evolution Reaction—The Enigma in Water Electrolysis

By E. Fabbri, Thomas J. Schmidt. ACS Catalysis, 2018

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in the metal oxide lattice, which can be replenished by a fi nal step by reacting with OH − in the electrolyte. Four electrons are overall exchanged in the LOER but decoupled proton electron steps take place. Step 2 and 3 are represented as formal reaction steps, but they would rather occur as a concerted process where H + and O 2 are released. The oxygen vacancy can be replenished by reaction with OH − (step 4), but also by H 2 O which can dissociate in hydroxide ion and a proton; the former fi lls an oxygen vacancy, while the latter can form a covalent bond with lattice oxygen. Proton incorporation via the dissociative adsorption of water has been widely discussed for proton conducting perovskites, such as BaZr 1 − Y . 57 − 59 In the fi gure, a perovskite structure AMO 3 has been used as representative catalyst where the orange, the green, the red, and the violet spheres represent the A-site cations, M-site cations, the oxygens (O), and the oxygen vacancies (V), respectively. For binary oxides, only the terminating MO layer can be considered.

Subfields: Electrical and Electronic Engineering, Electrochemistry, Renewable Energy, Sustainability and the Environment

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