Dear Collleagues,

The development of bifunctional materials that are able to catalyze oxygen-related reactions, i.e., the oxygen reduction (ORR) and the oxygen evolution (OER) reaction, is still a challenge for the progress of energy conversion and storage devices such as metal–air batteries or unitized regenerative fuel cells. These devices represent a promising future for a clean and sustainable conversion and storage of energy. Regenerative fuel cells produce H₂ and O₂ when acting as water electrolysers and provide electricity when acting as fuel cells fed with H₂. On the other hand, metal–air batteries are envisaged as next-generation batteries, with extraordinary high energy densities, being promising systems for portable, mobile or stationary applications. Oxygen electrodes can be very lightweight and thin because the active material, oxygen, does not need to be stored inside the cell. However, these electrodes are restricted by the poor reaction kinetics and low activity of many catalysts towards the oxygen evolution and reduction reactions.

In addition, it is a challenge to maintain the chemical and mechanical stability of the catalyst and supporting materials at oxidizing currents under the strong alkaline conditions commonly used, and under gas evolution. This Special Issue aims to cover the most recent advances and developments regarding bifunctional catalysts as oxygen electrodes.

Dr. Cinthia Alegre
Dr. David Sebastián
Prof. Dr. María Jesús Lázaro Elorri
Guest Editors

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• Metal–air batteries
• Fuel cells
• Oxygen reduction and/or evolution reactions
• Hydrogen oxidation and/or evolution reactions
• Advances in the design and synthesis of electrocatalysts
• Supports for bifunctional electrocatalysts
• Transition metal catalysts
• Water splitting