Atomic Hydrogen in Electrocatalytic Systems: Generation, Identification, and Environmental Applications

• H* generation mechanisms in various electrocatalytic systems are reviewed • Advances on H* identification and quantification protocols are reviewed • Regulation of H* generation using several typical cathodes is discussed • Efficiencies of different electrochemical reactors are compared • The principles of H* toward environmental application are discussed Electrochemical reduction has emerged as a viable technology for the removal of a variety of organic contaminants from water. Atomic hydrogen (H*) is the primary species generated in electrochemical reduction processes. In this work, identification and quantification for H* are reviewed with a focus on methods used to generate H* at different positions. Additionally, we present recently developed proposals for the surface chemistry mechanisms of H* on the most commonly used cathodes as well as the use of H* in standard electrochemical reactors. The proposed reaction pathways in different H* systems for environmental applications are also discussed in detail. As shown in this review, the key hurdles facing H* reduction technologies are related to i) the establishment of systematic and practical synthetic methods; ii) the development of effective identification approaches with high specificity; and, iii) an in-depth exploration of the H* reaction mechanism to better understand the reaction process of H*.