Enhancement of Photo‐ and Electrocatalytic H ₂ O ₂ Production by the Reversible Catechol‐to‐ <i>o</i> ‐Benzoquinone Transformation in Polydopamine

Abstract H 2 O 2 is an environmentally benign oxidant widely used in organic synthesis, wastewater treatment, disinfection, and the pulp and paper industry. While the industrial anthraquinone process enables large‐scale production of concentrated H 2 O 2 (30–70 wt%), it remains energy‐ and capital‐intensive due to its multi‐step nature, involving hydrogenation, oxidation, separation, concentration, and purification. Consequently, there is increasing interest in developing sustainable and decentralized methods for producing dilute H 2 O 2 (0.1–20 wt%) directly from H 2 O or O 2 . Light‐ and electricity‐driven O 2 reduction and/or H 2 O oxidation processes have emerged as promising strategies for efficient and cost‐effective H 2 O 2 generation. However, these approaches often suffer from low H 2 O 2 selectivity due to competing side reactions. Recent studies suggest that the reversible catechol‐to‐ o ‐benzoquinone transformation in polydopamine (PDA) can enhance photo‐ and electrocatalytic H 2 O 2 production. Despite its potential, the underlying mechanisms responsible for this improvement remain poorly understood. A deeper investigation into this reversible redox process is thus crucial for optimizing H 2 O 2 selectivity in photo‐ and electrocatalytic systems. This mini‐review highlights recent advances in PDA‐based catalysts for photo‐ and electrocatalytic H 2 O 2 production, focusing on key factors that improve H 2 O 2 selectivity. Building on these insights, we propose a generalized catalyst design strategy to achieve high H 2 O 2 selectivity in such systems.