Strategies and challenges on selective electrochemical hydrogen peroxide production: Catalyst and reaction medium design

Hydrogen peroxide (H2O2), as a valuable fuel and oxidant, has attracted increasing attention in the energy and environmentalrelated areas. The electrochemical oxygen reduction reaction (ORR) with a prominent 2-electron (2e(-)) pathway has been recognized as a ``green'' route for the direct synthesis of H2O2 and its on-site utilization. A systematic summary on rational design of catalyst systems (i.e., the catalyst and the reaction medium) for selective electrochemical H2O2 production is still lacking, which is critical for advancing this burgeoning field. Here, fundamental knowledge of electrochemical H2O2- related reactions including the reaction mechanism and the performance (activity, selectivity, and stability) descriptors is introduced in the beginning of this review. Afterward, the cutting-edge electrocatalyst and reaction medium (i.e., electrolyte) design strategies for H2O2 generation via 2e(-) ORR pathway are reviewed, with a special emphasis on selectivity regulation. Finally, critical perspectives are presented on the challenges and opportunities on the selective electrochemical H2O2 production.