Design and Performance Enhancement of Cobalt-Encapsulated Nitrogen-Doped Carbon Nanofiber Electrocatalyst through Ionic Liquid Modification for Efficient Oxygen Reduction

Abstract

The design of platinum-group-metal-free (PGM-free) electrocatalysts with appreciable activity and durability toward the oxygen reduction reaction (ORR) in acidic environments is a big challenge. Here, we report an efficient oxygen reduction activity of a Co-encapsulated nitrogen-doped carbon with nanofiber networks and its ionic liquid-modified interface in an acidic medium. The robust structure of the nanofibers embedded on a rigid framework derived from a zeolitic imidazole framework (ZIF-67) delivers promising activity and durability to the catalyst comparable to the state-of-the-art Pt/C. The ionic-liquid-modified catalyst shows a half-wave potential of 0.71 V vs RHE in oxygen-saturated 0.5 M H2SO4 along with activity reduction by only 11 mV (E 1/2) after 5000 cycles of the accelerated durability test. The catalyst also retains 71% of its original current during the short-term durability test. Furthermore, the electron transfer number and H2O2 yield of the catalyst during the ORR approaches 3.88–3.90 and 5.9–4.8% in the potential range 0.4–0.7 V vs RHE. The ORR performance of the ionic-liquid-modified catalyst is superior among all ionic liquid-based non-PGM catalysts reported so far in acidic media.

A Metal–Organic Framework-Derived Atomically Dispersed Yttrium as an Electrocatalyst for Oxygen Reduction Reaction

“…45,46 The high-resolution N 1s spectra further evidence the existence of pyridinic-N (398.1 eV), M−N x (399.7 eV), pyrrolic-N (400.9 eV), graphitic-N (401.6 eV), and pyridinic-N oxide (403.5 eV) type nitrogen in the catalyst (Figure S11b). 38,46 The deconvoluted Zn 2p and Y 3d XPS spectra illustrate the positive oxidation state of the respective elements with Zn 2p 3/2 and Y 3d 3/2 peaks shifted to 1021.4 and 159.9 eV, respectively, in comparison to their metallic states (Figure S11c,d). 38,40 This can be attributed to the existence of metal− nitrogen coordination.…”

A polypyrrole derived nitrogen doped porous carbon support for an atomically dispersed Mn electrocatalyst for the oxygen reduction reaction

“…The defect sites formed due to N-doping are known to facilitate O 2 adsorption in the electrocatalytic ORR. [37][38][39] The N 2 adsorption-desorption isotherms and pore size distribution curves of the Mn-N-C catalysts reveal the presence of large surface areas with micro-and mesoporous structures (Fig. 2c and d).…”

Highly Porous Polypyrrole (PPy) Hydrogel Support for the Design of a Co–N–C Electrocatalyst for Oxygen Reduction Reaction

“…The larger intensity ratio ( I D / I G ) of Co–N–C-0.02 with a higher Co content and N doping suggests that the atomic dispersion of Co is conducive to the formation of a disordered carbon structure . The defect sites are known to provide catalytic active centers for O 2 adsorption toward enhanced catalytic activity. ,− The N 2 adsorption–desorption isotherms and pore size distribution of the catalysts show similar surface area and the existence of both micro- and mesopores over a broad range (Figure S13c,d). The specific surface area, estimated by the Brunauer–Emmett–Teller (BET) method and total pore volume ranges between 411–493 m 2 /g and 1.49–1.60 cm 3 /g, respectively (Table S3).…”