Review and perspectives on carbon-based electrocatalysts for the production of H2O2via two-electron oxygen reduction

Abstract

As a versatile and environmentally friendly chemical, hydrogen peroxide (H₂O₂) is in high demand. The current anthraquinone oxidation process suffers from high energy consumption in hydrogen production and the cumbersome alternating operations of hydrogenation and oxidation. The direct synthesis of H₂O₂ from H₂ and O₂ is constrained by the balance between safety and efficiency and heavy metal pollution from catalysts. Two-electron oxygen reduction reaction (2e⁻ ORR) is an efficient, safe, and low-cost route for the production of H₂O₂. This 2e⁻ ORR pathway has potential to become a supplement to the anthraquinone process because of fossil energy-free feature. The bottleneck of the industrialization of 2e⁻ ORR is the lack of efficient catalysts. The 2e⁻ ORR catalytic performance of noble metal electrode materials urgently needs to be significantly enhanced by smart design. However, the high price and limited reserves of these noble metal-based materials still severely limit their commercialization. Among many 2e⁻ ORR catalysts, carbon-based catalysts have received much attention because of their low cost and diverse structures. This study reviews the research progress and the synthesis methods of carbon-based catalysts for 2e⁻ ORR in recent years. First, this paper introduces the fundamental mechanism of H₂O₂ production by 2e⁻ ORR through a combination of theory and experiment. Then, the synthesis methods and optimization strategies of various high-efficiency carbon-based catalysts are discussed. Finally, the various influencing factors (pH effect, pore structure, and carbon defects) and the practical applications for H₂O₂ production are analyzed. In addition, the future research direction is also proposed to promote the development of carbon-based catalysts for 2e⁻ ORR toward industrialization. Although carbon-based catalysts display obvious advantages for electrocatalytic applications, there are still a few shortcomings that need to be overcome. The intrinsic activity and the long-term stability of carbon-based materials still require to be improved to a level that can be compared with those of noble metal-based catalysts. This review presents a comprehensive overview of the latest developments in the production of H₂O₂ by 2e⁻ ORR on carbon-based catalysts, combining the most advanced theoretical and experimental literature available. The current state of the research on carbon-based catalysts in recent years indicates great promise for further advancement.