oxygenevolving

Oxygenevolving refers to processes that release molecular oxygen (O2), typically through the oxidation of water or other oxygen-containing substrates. In natural systems and in artificial devices, oxygen evolution is the final step that generates O2 as a byproduct of water oxidation.

In biological systems, the oxygen-evolving complex of photosystem II is the principal catalyst for water splitting during photosynthesis. It uses solar energy to oxidize water, producing O2, protons, and electrons. The reaction is classically represented as 2 H2O → O2 + 4 H+ + 4 e− and proceeds through a series of oxidation steps, often described by S-states, within a Mn4CaO5 cluster. This biological process supplies the oxygen in Earth's atmosphere and provides electrons and protons for subsequent biosynthetic reactions.

In electrochemistry and artificial photosynthesis, the oxygen evolution reaction (OER) is the anodic half-reaction of water splitting. The same overall reaction occurs, and its efficiency is governed by the overpotential required to drive the process and the kinetics of electron transfer. Catalysts are crucial for improving activity and durability; common materials include iridium oxide, ruthenium oxide, and various transition metal oxides or mixed-metal compounds. Research also targets earth-abundant catalysts such as nickel-iron oxides and cobalt-based materials, as well as novel nanostructured and perovskite-type catalysts.

Oxygenevolving is central to renewable energy technologies, particularly solar-to-fuels systems and photoelectrochemical cells, where water is split to produce hydrogen and oxygen. Performance is evaluated by oxygen evolution rate, faradaic efficiency, stability, and resistance to fouling or degradation. Challenges include minimizing overpotential, preventing catalyst corrosion, and scaling materials for large-scale production.