Metal‐Free Electrocatalyst for Oxygen Reduction: Synthesis‐Controlled Density of Catalytic Centers and Impact on ORR

Abstract

This work demonstrates a rapid and scalable route for the preparation of N‐doped carbon spheres of 80–120 nm via pyrolysis of polypyrrole as the only carbon and nitrogen source. The resulting porous catalyst has a nitrogen doping level of 6–8 at%. Electrochemical studies show that N‐doped C is very active toward oxygen reduction in alkaline electrolyte and the mechanism of ORR process is controlled by the surface concentration of catalytic active sites that promote either a direct four‐electron or two‐electron process. An interesting observation is that we can generate precursors for the N‐doped carbon with desirable particle size, shape and with the preferential structure (linear polypyrrole from the αα coupling during slow polymerization or cross‐linked polypyrrole from αβ coupling during fast polymerization) that promotes the formation of favorable catalytic sites for O2 reduction. The XPS analysis in conjunction with RDE voltammetry highlights the effect of polymer precursor synthesis on the chemical structure and a resulting electrochemical activity of the N‐doped carbon materials.

N, S-Codoped Porous Carbon with Densely Edge Structure for Oxygen Reduction Reaction and Zinc-Air Battery

“…40 Moreover, the high content of pyrrolic N also contributes to the improved catalytic performance of ORR by modulating the adsorption of O 2 molecules and the electron transport properties. 48 The similar external surface area to the specific surface area indicates abundant micropores on the surface of the catalysts, which contribute to the exposure of active sites and the utilization of efficient active sites.…”

General Doping Chemistry of Carbon Materials

“…Various precursors and synthetic methods have been worked to make heteroatom‐doped carbon materials [77] . These structural features of the materials affect the electrocatalytic properties, such as electrocatalytic activity and electrical conductivity [78] . For instance, doping with alkali metals enhances the conductivity, e. g., producing superconductivity of fullerenes, diamond, and graphite.…”

“…[77] These structural features of the materials affect the electrocatalytic properties, such as electrocatalytic activity and electrical conductivity. [78] For instance, doping with alkali metals enhances the conductivity, e. g., producing superconductivity of fullerenes, diamond, and graphite. Undoped diamond is an insulator, but the diamond has been turned up to become a superconductor after it undergoes a metal-insulator transition by B-doping.…”

Nanostructured conducting polymers for energy applications: towards a sustainable platform

“…Dispersion and size distribution of NP catalysts are achieved on CPNs for maximum exploitation and fast kinetics which tend to provide a way to decrease the catalyst loading. [211][212][213] in comparison to their bulk counterparts, CP nanostructure supported catalytic materials can display improved electrode activities for ethanol oxidation which can be useful for direct ethanol fuel cells (DFFCs). 213 A series of Pt NP based electrocatalysts supported on CPs have been used for the electrocatalytic oxidation of methanol.…”