Fe/Fe₃C Nanoparticles Encapsulated in N‐Doped Hollow Carbon Spheres as Efficient Electrocatalysts for the Oxygen Reduction Reaction over a Wide pH Range

Abstract

Nonprecious‐metal‐based electrocatalysts with low cost, high activity, and stability are considered as one of the most promising alternatives to Pt‐based catalysts for the oxygen reduction reaction (ORR). Herein, an economical and easy‐to‐fabricate catalyst is developed, that is, Fe/Fe3C embedded in N‐doped hollow carbon spheres (Fe/Fe3C/NHCS), which gave the half‐wave potential of 0.84 V in 0.1 m KOH, similar to the commercial Pt/C catalyst. Surprisingly, the favorable ORR performance of the as‐prepared catalyst was obtained in both acidic and neutral conditions with almost a four‐electron pathway and low H2O2 yield, which desirable the development of the proton exchange membrane (PEM) and microbial electrolysis cell (MEC) technology. Additionally, the obtained catalyst demonstrated better long‐term stability and high methanol tolerance over a wide range of pH. These features could be mainly attributed to the synergistic effect between Fe/Fe3C and Fe‐Nx sites, the hollow structure with mesopores, and the well‐dispersed Fe/Fe3C nanoparticles owing to the existence of the abundant hydrophilic groups within the HCS precursor. As such, designing an efficient and cheap ORR catalyst that can operate at alkaline, acidic, and neutral solutions is highly desirable, yet challenging.

An Fe-N/S-C hybrid electrocatalyst derived from bimetal-organic framework for efficiently electrocatalyzing oxygen reduction reaction in acidic media

“…The linearity of the Koutecky-Levich (K-L) plots and the near parallelism of the fitting lines (inset in Fig. 9b) indicate first-order reaction kinetics with respect to the concentration of the dissolved O 2 and 4e selectivity for ORR at different potentials [32][33][34][35]. To identify the ORR catalytic pathway at Fe-N/S-C-10%, the rotating ring-disk electrode (RRDE) technique was adopted, in which the amount of H 2 O 2 generated at the disk electrode is accurately determined by the ring current (Fig.…”

Nitrogen-doped iron for selective catalytic reduction of nitrate to dinitrogen

“…Meanwhile, a sharp peak at 26.2°and a board peak at 43.2°were corresponded to (0 0 2) and (1 0 1) planes of graphitized carbon (JCPDS No. [20,30]. The FeN-NC-140 showed the broadest Fe 0 /FeN peak with limited observation of a-Fe peak, indicating that Fe was prone to present either individually as zero-valent iron or covalently as participant in nitride iron [26,37].…”

“…Among various N containing moieties, graphitic carbon nitride (g-C 3 N 4 ) derived from sp 2 hybridization of C and N has been frequently used as an N precursor for high doping efficiency, due to the rich N content and multiple lone-pair electrons for coordination [24][25][26][27][28]. To stabilize the active iron as a catalyst, a nitridecarbon (NC) shell is constructed to further regulate the electron transfer pathway of FeN, resulting in prolonged catalytic activity and enhanced N 2 selectivity [29,30]. Carbonized glucose is thoroughly coated onto graphitized g-C 3 N 4 template for the growth of NC shell [31].…”

Trace Iridium Engineering on Nickel Hydroxide Nanosheets as High‐active Catalyst for Overall Water Splitting

“…[11][12][13][14] Currently, numerous potential electrocatalysts for HER in acidic electrolyte and OER in basic electrolyte have been designed. [15][16][17][18] However, powerful electrocatalysts with high efficiency for both HER and OER as well as operating in various electrolytes are still rare. Therefore, it is urgent to fabricate the pH-universal bifunctional electrocata-lysts with high catalytic activity and stability for water splitting electrolyzer.…”

“…On the other hand, an ideal electrocatalyst needs to adapt to different systems under multi‐pH conditions, such as acidic, basic, and especially for neutral conditions, because of the abundant resources of seawater [11–14] . Currently, numerous potential electrocatalysts for HER in acidic electrolyte and OER in basic electrolyte have been designed [15–18] . However, powerful electrocatalysts with high efficiency for both HER and OER as well as operating in various electrolytes are still rare.…”