Single‐Atom Catalysts for H₂O₂ Electrosynthesis via Two‐Electron Oxygen Reduction Reaction

Abstract

Oxygen reduction reaction via the two-electron route (2e − ORR) provides a green method for the direct production of hydrogen peroxide (H 2 O 2 ) along with in situ utilization. The effective catalysts with high ORR activity, 2e − selectivity, and stability are essential for the application of this technology. Single-atom catalysts (SACs) have attracted intensively attention for H 2 O 2 electrosynthesis owing to the unique geometric and electronic configurations. In this review, the mechanism and theoretical predictions for 2e − ORR over SACs are first introduced. Then, the recent advances of various SACs for the electrosynthesis of H 2 O 2 are documented. And the correlation between the central atom, coordination atoms, and coordination environment of SACs and the corresponding electrocatalytic ORR performance including activity, selectivity, and stability are emphatically analyzed and summarized. Finally, the major challenges and opportunities regarding the future design of SACs for the H 2 O 2 production are pointed out.

Constructing single atom sites on bipyridine covalent organic frameworks for selective electrochemical production of H2O2

“…This observation confirms the successful synthesis of imine-linked Py-Bpy-COF. This result is further confirmed by the 13 C solidstate nuclear magnetic resonance ( 13 C NMR). As shown in Fig.…”

“…Single-atom catalysts (SACs) have garnered significant attention in the application of the ORR for H 2 O 2 synthesis owing to their distinctive geometric and electronic structures, along with exceptional atom utilization efficiency. [12][13][14] Although some progress has been made in the past few years, 12,13 most reported SACs toward 2e À ORR are synthesized by hightemperature uncontrollable pyrolysis, which makes it hard to obtain well-defined and uniformly distributed metal centers. Also, it brings difficulty in establishing a clear relationship between the structure and performance.…”

Non‐precious Metal Catalysts for Two‐Electron Oxygen Reduction Reaction

“…[33] For full utilization of metal active sites, the concept of single atom catalysts (SACs) has been extensively studied in various fields of electrocatalysis. [5,8,[34][35][36] The metal single atoms are distributed onto the carbon support at the atomic level, enabling full utilization of the catalytic activity.…”

“…The reaction proceeds via either pathway depending on the adsorption type of O 2 . [34] In side-on adsorption of O 2 , the reaction proceeds mostly via four-electron pathways. On the other hand, for end-on adsorption, O 2 can be adsorbed either via Griffiths-type mode or Yeagertype mode.…”

“…[41,43,54,55] The concept of a SAC also induces endon adsorption by separating active sites. [34,42,44,56,57] For practical applications of electrochemical synthesis of hydrogen peroxide, more economically viable electrocatalysts are needed. The earth-abundant non-precious metal-based catalysts in the form of heterogenized catalysts of a transition metal-N x moiety with and without a carbon support (MeÀ N x and MeÀ N x /C), SAC, and metal-organic frameworks (MOFs) are suitable for this purpose.…”