Oxygen Evolution Reaction at Carbon Edge Sites: Investigation of Activity Evolution and Structure–Function Relationships with Polycyclic Aromatic Hydrocarbons

Abstract

The abundance of available surface chemical information and edge structures of carbon materials have attracted tremendous interest in catalysis. For the oxygen evolution reaction (OER), the edge effects of carbon materials have rarely been studied in detail because of the complexity of various coexisting edge configurations and the controversy between carbon corrosion and carbon catalysis. Herein, the exact roles of common carbon active edge sites in the OER were interrogated using polycyclic aromatic hydrocarbons (PAHs) with designated configurations (zigzag and armchair) as model probe molecules, with a focus on structure–function relationships. Zigzag configurations of PAHs showed high activity for the OER while also showing a good stability at a reasonable potential. They show a TOF value of 0.276 s −1 in 0.1 m KOH. The catalytic activity of carbon edge sites was further effectively regulated by extending the π conjugation structure at a molecular level.

Nanostructured Carbon Based Heterogeneous Electrocatalysts for Oxygen Evolution Reaction in Alkaline Media

“…In recent years, enormous research efforts have been directed to investigate the edge chemistry and defect engineering of nanocarbon materials due to their importance for electronic properties and surface reactivity . The edge‐induced topological defects are reported to redistribute the local electron density and offer a strong affinity to the reaction intermediates during OER process.…”

“…A concise summary on the doping elements, precursors, doping levels, electrolytes, and electrocatalytic performances of single‐element‐doped and multi‐elements‐doped metal‐free nanocarbons are given in Table and Table , respectively. Additionally, topological edge dangling bonds and defective sites in dopant‐free nanocarbons can significantly contribute to the electrocatalytic performances . Some of edge‐ and defect‐rich metal‐free nanocarbons are summarized including precursors, synthetic methods, electrolytes, and electrochemical performances in section 2.3.…”

“…So far, various engineering methods for producing the edge and defect on the nanocarbons have been explored, including high‐temperature reduction, chemical reduction, ball‐milling method, and plasma treatment, etc. In particular, edge‐ and defect‐rich dopant‐free nanocarbon based materials as metal‐free catalysts play vial roles in OER electrocatalysis due to their economic viability, high conductivity, surface chemistry, tunable structure, as well as remarkable activity …”

Investigating the Integrity of Graphene towards the Electrochemical Oxygen Evolution Reaction

“…As one can see in Figure A, the electrochemical performance of mono‐layer graphene towards the OER decays when successive scans are completed; note also that the electrochemical signal of the first scan is highly likely perturbed by bubbles being formed upon the graphene electrode's surface, which are oxygen bubbles being formed as a result of the OER occurring at edge plane sites/defects on the basal plane graphene surface. The origin of electron transfer properties at pristine graphene has been recently confirmed to happen at the edges particularly for the OER application, zigzag edge configurations give better performance than armchair motifs, playing both a positive role in the OER …”

“…As a result, there is interest in developing graphene‐based catalysts using innovative strategies including surface functionalization, geometric arranging and heteroatom doping . It is important to add the highlight of studies regarding pristine 2D graphene (CVD) application, large‐quantity synthesis and integration for energy applications, and the effect of the graphene's edge structures because of the high complexity of coexisting edge configurations . Therefore, there is a need to fundamentally understand the intrinsic relationship of the bare graphene structures (mono, few, multi) correlated to electrochemical performance for the future application of CVD graphene‐based catalysts.…”