关键词: 电化学, 二电子氧还原反应, 过氧化氢, 催化剂, 选择性

Abstract:

Hydrogen peroxide (H₂O₂) is an important chemical and has been extensively used in various industrial and manufacturing applications, such as wastewater treatment, sterilization, energy storage, and oxidation of small molecules. With increasing demand in various fields, the global hydrogen peroxide market is expected to grow to ＄8.9 billion by 2031. Currently, over 90% of H₂O₂ is industrially synthesized by the anthraquinone process, which requires complex infrastructure and expensive catalysts. Additionally, the anthraquinone process is energy intensive and leads to increased levels of environmental pollution. Although the direct synthetic process, which involves mixing hydrogen and oxygen, can achieve high atomic utilization, its development is limited due to explosion risk and high cost. Thus, there is a pressing need for a safe, cost-effective, and efficient industrial method for the production of H₂O₂. The electrochemical synthesis of H₂O₂ via a two-electron oxygen reduction reaction (2e⁻ ORR) has emerged as an attractive method for the decentralized production of H₂O₂, which could effectively address the issues associated with the indirect anthraquinone and direct synthetic processes. However, sluggish reaction kinetics and poor selectivity decrease the energy efficiency of electrochemical H₂O₂ synthesis. In this regard, developing electrocatalysts with high 2e⁻ ORR selectivity is vital for the efficient production of H₂O₂. In the past decades, extensive efforts have been devoted to developing effective 2e⁻ ORR electrocatalysts such as noble metals/alloys, carbon-based materials, single-atom catalysts, and molecular complexes. However, the reported catalysts still have unsatisfactory catalytic performances. Therefore, there is still a long way to realize the large-scale production of H₂O₂ via electrochemical 2e⁻ ORR pathway. In this perspective, we systematically summarize recent developments regarding the direct production of H₂O₂ through electrochemical two-electron oxygen reaction. First, the fundamental aspects of electrochemical 2e⁻ ORR are discussed, including their reaction mechanisms, possible reaction pathways, testing techniques and performance figures of merit. This introduction is followed by detailed discussions on the different types of 2e⁻ ORR electrocatalysts, with an emphasis on the underlying material design principles used to promote reaction activity, selectivity, and stability. Subsequently, the applications of electrosynthetic hydrogen peroxide in various fields are briefly described, including pollutant degradation, water sterilization, energy storage, and small-molecule synthesis. Finally, potential future directions and prospects in 2e⁻ ORR catalysts for electrochemically producing H₂O₂ are examined.

Key words: Electrochemical, 2e^? oxygen reduction reaction, Hydrogen peroxide, Catalyst, Selectivity