OER Reaction Mechanism: AEM vs. LOM Explained

Currently, there exist two primary formulations of the OER reaction mechanism: AEM34, 35 and LOM36, 37. Figure 1a14, 38, 39 depicts the traditional AEM, which comprises four proton-electron transfer processes with metal serving as the active site. The oxygen product is derived from absorbed water molecules. Initially, a water molecule is adsorbed on the metal site (M) of the electrocatalyst through a one-electron oxidation step, wherein it loses a proton simultaneously to form adsorbed *OH. The adsorbed *OH species is then oxidized, transferring one proton and electron, to *O. Another water molecule subsequently conducts a nucleophilic attack on the oxygen species to produce the *OOH intermediate. Finally, the *OOH adsorbed on the metal site is further oxidized, followed by desorption to release a dioxygen molecule. In contrast, LOM (depicted in Figure 1b37, 39, 40) involves lattice oxygen of the catalysts in the oxygen evolution process and directly engages in OO coupling. The LOM pathway provides a unique reaction pathway for O-O coupling, and its reaction energy is not limited by the adsorption energy scaling relationship of the AEM pathway.