What type of reaction occurs in hydrogen-oxygen fuel cells?

In hydrogen-oxygen fuel cells, a redox reaction occurs. This type of reaction involves the transfer of electrons between two species, allowing both oxidation and reduction processes to take place simultaneously. In the specific case of hydrogen-oxygen fuel cells, hydrogen gas (H₂) is oxidized at the anode, losing electrons, while oxygen gas (O₂) is reduced at the cathode, gaining those electrons. This electron transfer generates electrical energy, which is the primary function of the fuel cell.

While other types of reactions are mentioned, they do not accurately describe the processes happening within a hydrogen-oxygen fuel cell. A synthesis reaction typically involves two or more reactants combining to form a single product, whereas a decomposition reaction involves a single compound breaking down into simpler substances. Exothermic reactions, though relevant since they release energy, do not specifically define the electron transfer that is characteristic of redox reactions. Therefore, the classification of the reaction in a hydrogen-oxygen fuel cell as a redox reaction is both precise and essential for understanding its operation.