F‐Doped Co−N−C Catalysts for Enhancing the Oxygen Reduction Reaction in Zn‐Air Batteries

Abstract

Zn‐air battery is a promising next‐generation energy storage device. Its performance, however, is limited by a high overpotential resulted from the slow kinetics of the cathodic oxygen reduction reaction (ORR). This study reports a simple strategy for preparation of a fluorine‐doped Co−N−C composite as highly efficient electrocatalyst for ORR. The C@PVI‐(TPFC)Co‐800 catalyst was prepared by pyrolysis of F‐containing Co‐corrole that was assembled on PVI‐functionalized carbon black through the axial imidazole coordination (PVI=polyvinylimidazole, TPFC=5,10,15‐triperfluorophenyl‐21H, 22H‐corrole). The C@PVI‐(TPFC)Co‐800 catalyst exhibited much more positive ORR half‐wave potential (E1/2=0.88 V vs. RHE) than its counterpart C@PVI‐(TPC)Co‐800 (E1/2=0.82 V, TPC=5,10,15‐triphenyl‐21H, 22H‐corrole) without F‐doping in 0.1 M KOH electrolyte. C@PVI‐(TPFC)Co‐800 also achieved a greater kinetic current density and enhanced durability in alkaline media. In addition, a Zn‐air battery with C@PVI‐(TPFC)Co‐800 loaded at the cathode delivered much higher peak power density (Pmax=141 mW/cm2) and open‐circuit voltage (OCV=1.45 V) over the C@PVI‐(TPC)Co‐800 counterpart (Pmax=110 mW/cm2, OCV=1.39 V) and the commercial 20 % Pt/C (Pmax=119 mW/cm2, OCV=1.42 V) as well. The promoted catalyst performance for ORR was attributed to the increased specific surface area, more defects generated, and reduced electron density distribution around the Co metal center after F‐doping.

Tailoring single-metal atom catalysts: a strategic defect engineering approach for electrochemical reduction reactions

“…In 2023, Xu and colleagues investigated fluorine doping, which aided in the formation of additional defects for the stabilization of Co based single metal atoms on porous carbon. 166 The XPS analysis of the catalyst C@PVI-(TPFC)Co-800 showed the presence of elements like C, F, N, O and Co, indicating a comprehensive doping profile, as shown in Fig. 20(k).…”

Regulating the Electronic Configuration of Single-Atom Catalysts with Fe–N5 Sites via Environmental Sulfur Atom Doping for an Enhanced Oxygen Reduction Reaction

“…Constructing dual-metal atomic sites could utilize the short/medium-range interactions with another metal to optimize the charge density and the adsorption configurations of key ORR intermediates, thus boosting the intrinsic activity of ORR catalysts . Apart from modifying the metal center, engineering the local carbon structure around active sites (local carbon strain engineering or defect engineering) could change the electronic structure of the metal center, thereby kinetically increasing the ORR activity. , The edge-hosted M-N x sites were reported to show a higher ORR activity than the in-plane-hosted M-N x sites due to the defect-induced rearrangement of the electron density. , In addition, heteroatom doping (e.g., S, P, and halogens) to modulate the intrinsic activity of M-N x sites represents an attractive approach. − Sulfur, as a p-block element, is similar to nitrogen but with a lower electronegavity. , Therefore, rational introducing of the electron-donating S atoms into the catalyst composite could regulate the electronic structure of the metal center. Chen et al prepared an efficient ORR catalyst by pyrolyzing a metal–organic framework precursor and a methimazole ligand, in which S atoms were doped into the environmental carbons and FeS nanoparticles were formed as well .…”