Redefining Water Oxidation Selectivity Through Electrolyte Microenvironment Engineering

ABSTRACT The two‐electron water oxidation reaction (2e − WOR) offers a sustainable route to in situ H 2 O 2 production from water, distinct from the anthraquinone process and direct H 2 /O 2 synthesis. Its central challenge is the competition between H 2 O 2 formation and the four‐electron oxygen evolution reaction (OER), governed by water polarization, hydroxyl‐intermediate formation, O─O bond construction, peroxy‐species desorption, and product stability. Because catalyst‐site regulation alone rarely optimizes selectivity, stability, and productivity simultaneously, the electrolyte microenvironment becomes a critical reaction variable. Through specific ion adsorption, electric‐double‐layer reconstruction, local pH control, solvation and hydrogen‐bond‐network regulation, and interfacial electric fields, electrolytes reshape intermediate configurations, proton‐electron transfer barriers, and H 2 O 2 decomposition. This Review introduces the framework of “electrolyte‐encoded reaction pathways” to describe how electrolyte‐derived interfacial states differentially regulate competing H 2 O 2 ‐forming channels. It distinguishes direct surface‐mediated 2e − WOR, electrolyte‐assisted direct 2e − WOR, and indirect electrolyte‐mediated anodic H 2 O 2 synthesis, thereby separating pathway regulation from reaction‐network reconstruction. By linking electrolyte descriptors and catalyst‐electrolyte coupling to selectivity, H 2 O 2 stability, and system‐level performance, this framework redefines the electrolyte as an active variable in reaction‐network design.