Electrocatalytic Oxygen Reduction to Hydrogen Peroxide: From Homogeneous to Heterogeneous Electrocatalysis

Abstract Hydrogen peroxide (H 2 O 2 ) is an environmentally friendly oxidant, finding widespread use across the chemical industry, in sanitation and environmental remediation. Currently, H 2 O 2 is manufactured via the anthraquinone process which has a number of disadvantages including nondistributed production, high‐energy consumption, substantial organic by‐product waste, and the need to transport the obtained H 2 O 2 to the point‐of‐use. Accordingly, the electrochemical synthesis of H 2 O 2 is now attracting a lot of interest as an alternative, cost‐effective, small‐scale, and distributed technology for H 2 O 2 manufacture. This review summarizes recent advancements in the development of Homogeneous and Heterogeneous catalysts for electrocatalytic O 2 reduction reaction (ORR) to H 2 O 2 . The basic principles of the ORR, and methodologies for investigating the ORR to H 2 O 2 are first introduced. Next, H 2 O 2 production over Homogeneous catalysts is discussed, with a focus on the reaction mechanisms and the factors that influence activity, selectivity, and reaction kinetics. Subsequently, recent breakthroughs in H 2 O 2 synthesis over Heterogeneous catalysts, including nonnoble metal‐based nanomaterials, carbon materials, and single‐atom catalysts are described. The latter are given special attention, since they serve as a bridge between Homogeneous catalysis and Heterogeneous catalysis, while also offering excellent performance. Finally, the challenges and opportunities for electrochemical ORR to H 2 O 2 are critically discussed.