Metal‐Free Multi‐Heteroatom‐Doped Carbon Bifunctional Electrocatalysts Derived from a Covalent Triazine Polymer

Abstract

The construction of multi‐heteroatom‐doped metal‐free carbon with a reversibly oxygen‐involving electrocatalytic performance is highly desirable for rechargeable metal‐air batteries. However, the conventional approach for doping heteroatoms into the carbon matrix remains a huge challenge owing to multistep postdoping procedures. Here, a self‐templated carbonization strategy to prepare a nitrogen, phosphorus, and fluorine tri‐doped carbon nanosphere (NPF‐CNS) is developed, during which a heteroatom‐enriched covalent triazine polymer serves as a “self‐doping” precursor with C, N, P, and F elements simultaneously, avoiding the tedious and inefficient postdoping procedures. Introducing F enhances the electronic structure and surface wettability of the as‐obtained catalyst, beneficial to improve the electrocatalytic performance. The optimized NPF‐CNS catalyst exhibits a superb electrocatalytic oxygen reduction reaction (ORR) activity, long‐term durability in pH‐universal conditions as well as outstanding oxygen evolution reaction (OER) performance in an alkaline electrolyte. These superior ORR/OER bifunctional electrocatalytic activities are attributed to the predesigned heteroatom catalytic active sites and high specific surface areas of NPF‐CNS. As a demonstration, a zinc‐air battery using the NPF‐CNS cathode displays a high peak power density of 144 mW cm−2 and great stability during 385 discharging/charging cycles, surpassing that of the commercial Pt/C catalyst.

Recent advances in heterostructured cathodic electrocatalysts for non-aqueous Li–O2batteries

“…More importantly, they can also show excellent catalytic property for boosting ORR. 113,114 Their OER catalytic activity, 52 however, is evidently insufficient, largely limiting their practical Li-O 2 battery performance. 116,117 Therefore, it is necessary to employ the bifunctional cathode catalysts with excellent performance towards both ORR and OER by constructing the heterogeneous structures containing carbon materials and active OER catalytic materials.…”

Air Electrodes for Flexible and Rechargeable Zn−Air Batteries

“…are usually introduced into the carbon matrix to tune the partial electronic structure and change the charge density distribution of carbon, leading to the improvement of catalytic activity. [ 163–166 ] Generally, nitrogen doping was widely investigated, and DFT calculations suggested that the carbon atoms situated at the armchair edge and adjacent to the graphitic N dopants acted as more active sites for the ORR and OER. [ 167–170 ] Marcilla et al reported a kind of CNT fiber fabricated by direct chemical vapor deposition (CVD) spinning and then treated by a facile hydrothermal reaction with urea.…”

Recent Advancements in the Synthesis and Application of Carbon-Based Catalysts in the ORR

“…The use of polymers as starting materials for synthesizing carbon based electrocatalysts have gained particular interest in the research field of ORR [41]. Doping has been used as a method to incorporate heteroatoms such as N, P, and fluorine (F) into the active sites of the carbon matrix to improve its performance [42,43]. This process requires the mixing of carbon precursors with different heteroatom sources through multiple steps [42][43][44].…”

“…Doping has been used as a method to incorporate heteroatoms such as N, P, and fluorine (F) into the active sites of the carbon matrix to improve its performance [42,43]. This process requires the mixing of carbon precursors with different heteroatom sources through multiple steps [42][43][44]. However, some research studies have been performed using a single precursor to prepare heteroatom-doped carbon as electrocatalysts for ORRs.…”