Molecular Design of Porous Organic Polymer-Derived Carbonaceous Electrocatalysts for Pinpointing Active Sites in Oxygen Reduction Reaction

Abstract

The widespread application of fuel cells is hampered by the sluggish kinetics of the oxygen reduction reaction (ORR), which traditionally necessitates the use of high-cost platinum group metal catalysts. The indispensability of these metal catalysts stems from their ability to overcome kinetic barriers, but their high cost and scarcity necessitate alternative strategies. In this context, porous organic polymers (POPs), which are built up from the molecular level, are emerging as promising precursors to produce carbonaceous catalysts owning to their cost-effectiveness, high electrical conductivity, abundant active sites and extensive surface area accessibility. To enhance the intrinsic ORR activity and optimize the performance of these electrocatalysts, recognizing, designing, and increasing the density of active sites are identified as three crucial steps. These steps, which form the core of our review, serve to elucidate the link between the material structure design and ORR performance evaluation, thereby providing valuable insights for ongoing research in the field. Leveraging the precision of polymer skeletons based on molecular units, POP-derived carbonaceous catalysts provide an excellent platform for in-depth exploration of the role and working mechanism for the specific active site during the ORR process. In this review, the recent advances pertaining to the synthesis techniques and electrochemical functions of various types of active sites, pinpointed from POPs, are systematically summarized, including heteroatoms, surficial substituents and edge/defects. Notably, the structure–property relationship, between these active sites and ORR performance, are discussed and emphasized, which creates guidelines to shed light on the design of high-performance ORR electrocatalysts.

Graphitic Carbocatalysts with Pentagon Defects Synthesized from Polyperylene for Electrocatalytic Oxygen Reduction and Flexible Zinc-Air Batteries

“…To tackle these issues, carbocatalysts have garnered significant researchers’ attention and emerged as a potential alternative, considering their relatively low cost and better stability. − Typically, the fabrication of functional carbocatalysts can be achieved through methods such as doping, activating, or etching various carbon substrates at the nanoscale, , collectively referred to as post-treatment techniques. Alternatively, carbocatalysts can also be directly derived from the thermal treatment of porous organic polymers, , a process commonly termed the bottom-up approach. This method facilitates the formation of carbonaceous materials endowed with diverse functionalities and nanoscale properties.…”

Cobalt Phthalocyanine-Doped Polymer-Based Electrocatalyst for Rechargeable Zinc-Air Batteries

“…However, porous carbon materials synthesised using these methods suffer severe degradation at high voltage conditions in RZABs due to their insufficient graphitisation levels [ 18 , 19 , 20 ]. Thus, porous carbon-based catalysts derived from the rigid polymer precursors embedded transition metal dopants that undergo controlled pyrolysis result in desirable structures, compositions, and electrocatalytic properties [ 21 , 22 , 23 ]. Moreover, porous carbon derived from polymer-network materials possesses tuneable textural properties, high surface area, and good electrical conductivity [ 24 ].…”