Noble metal-free single-atom electrocatalysts and reactor engineering for enhanced hydrogen peroxide generation via two-electron oxygen reduction reaction

The generation of hydrogen peroxide (H 2 O 2 ), a compound with diverse applications, via the two-electron (2e − ) oxygen reduction reaction (ORR) has garnered extensive attention in both laboratory research and industrial settings. The integration of non-noble metals such as Co, Fe, Ni, Zn, Mn, Mo, or Bi into nitrogen-doped carbon (M–N–C) matrices with defined structures and active metal center sites has emerged as a promising approach for fabricating electrocatalysts for the ORR. This review uncovers the latest advancements in the development of noble metal-free single-atom electrocatalysts (M–N–C SAECs) and electrochemical reactors aimed at enhancing and stabilizing H 2 O 2 production from the 2e − ORR. Firstly, the review explores the basics of the ORR for H 2 O 2 production and the impact of electrochemical conditions. Subsequently, the synthesis strategies and characterization methods of various M–N–C SAECs are examined in depth. In addition, the structural attributes of both conventional and altered M–N–C SAECs are meticulously investigated, and the importance of engineering and optimizing reactors to elevate H 2 O 2 yields is highlighted. This review identifies the challenges and technological hurdles in bridging the gap between laboratory-scale research and practical, real-world applications. • The principles underlying direct H 2 O 2 production are examined. • The synthesis approaches and characterization techniques for M–N–C SAECs are analyzed. • The structural characteristics of M–N–C SAECs are explored. • The optimizing reactors for enhancing H 2 O 2 electrosynthesis are emphasized. • Barriers in transitioning from laboratory to real-world applications are addressed with future perspectives.