Pyrazinium ionic liquid for preparing a 0D/2D hybridized N,P-codoped carbon enriched with pyridinic N and its enhanced electrocatalytic performance toward the oxygen reduction reaction

Abstract

Given their low volatility and heteroatom-rich composition, ionic liquids (ILs) are considered excellent precursors for fabricating various porous heteroatom-modified carbon materials, which exhibit good electrocatalytic activity for the oxygen reduction reaction (ORR). In the heteroatom-doped carbons, the pyridinic N-doped carbon is considered the active sites. Herein, a pyrazine IL that structurally resembles the pyridinic N-doped carbon is selected as the precursor for synthesizing a N,P-codoped carbon (C_pyr) material, which exhibits a high pyridinic N content of 19.2 at%, in contrast to the pyridinic N content of 11.2 at% of the control sample (C_mim) derived from 2-methylimidazole. The pyrazine IL-derived C_pyr has a unique 0D/2D hybridized morphology and a larger electrochemical surface area, while C_mim displays the general sheet-like appearance. The high pyridinic N content and unique 0D/2D hybridized structure synergistically enhance the ORR performance of C_pyr. The onset potential and half-wave potential of C_pyr are 0.94V_RHE and 0.75V_RHE and those of C_mim are 0.90V_RHE and 0.58V_RHE, respectively. Thus, this work provides a promising strategy to prepare highly electroactive carbon materials via the rational design of IL precursors at the molecular level.