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

Hydrogen peroxide (H2O2) is an environmentally friendly oxidant, finding widespread use across the chemical industry, in sanitation and environmental remediation. Currently, H2O2 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 H2O2 to the point‐of‐use. Accordingly, the electrochemical synthesis of H2O2 is now attracting a lot of interest as an alternative, cost‐effective, small‐scale, and distributed technology for H2O2 manufacture. This review summarizes recent advancements in the development of Homogeneous and Heterogeneous catalysts for electrocatalytic O2 reduction reaction (ORR) to H2O2. The basic principles of the ORR, and methodologies for investigating the ORR to H2O2 are first introduced. Next, H2O2 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 H2O2 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 H2O2 are critically discussed. Hydrogen peroxide (H2O2) is widely used as a green oxidant in chemical industries and environmental remediation. This review summarizes recent advances in the design and development of Homogeneous catalysts and Heterogeneous electrocatalysts for the oxygen reduction reaction (ORR) to H2O2. Finally, the challenges and opportunities for electrochemical ORR to H2O2 are critically discussed to offer insights in this field.