ZIF-67-Derived Dodecahedral Co@N-Doped Graphitized Carbon Protected by a Porous FeS₂Thin-Layer as an Efficient Catalyst to Promote the Oxygen Reduction Reaction

Abstract

The oxygen reduction reaction (ORR) plays an irreplaceable role in many energy-conversion processes. Low-cost catalysts with high activity and stability are eagerly needed to improve the sluggish ORR kinetics. Herein, we use a simple hydrothermal method to evenly deposit iron disulfide (FeS2, as shell) on the surface of dodecahedral Co@N-doped graphitized carbon (Co@DNC, as core) with ZIF-67 dodecahedrons as the precursor. Co@DNC@FeS2-0.5 (Co@DNC-to-FeCl3·6H2O mass ratio of 0.5) catalyst shows a comparable ORR catalytic activity (onset potential of 0.942 V and half-wave potential of 0.846 V, vs reversible hydrogen electrode) to commercial Pt/C (20 wt %) in alkaline media. The charge transfer resistance (4.06 Ω) of Co@DNC@FeS2-0.5 is smaller than that of Pt/C (6.72 Ω), indicating that Co@DNC@FeS2-0.5 facilitates a fast Faradaic process and charge transfer kinetics for the ORR. The core@shell structure and highly active moieties of Co@DNC@FeS2-0.5 contribute to the high ORR activity. DNC-wrapped Co/CoO (originated from the oxidation of surface Co0) possesses the positive charges to prioritize the adsorption of O2 on the Co–N x (Co atom binds to pyridinic N) active sites, and then, the S–S bonds in FeS2 with multivalent redox activity can supply/transfer the electrons to Co–N x to boost the ORR via a 4e– pathway. Moreover, the DNC@FeS2 shell with a porous structure can protect the active sites on the Co cores and accelerate the mass transfer of ORR-related species (O2, OH–, etc.) to the active sites. This study provides a novel strategy to enhance ORR activity using the core@shell structured catalysts originating from zeolite imidazole frameworks.

2D/3D-Shaped Fe0.8Ni0.2S2/ZIF-67 as a Nanozyme for Rapid Measurement of H2O2 and Ascorbic Acid with a Low Limit of Detection

“…Fe 0.8 Ni 0.2 S 2 /ZIF-67 was fabricated by a hydrothermal method, where the experimental conditions were similar as the synthesis of FeS 2 . Fe­(NO 3 ) 3 ·9H 2 O (3.636 g), Ni­(NO 3 ) 2 ·6H 2 O (0.291 g), and Na 2 S·9H 2 O (2.400 g) were dissolved in deionized water.…”

Trimetallic Mo-/Ni-/Fe-Based Hybrids Anchored on Hierarchical N-CNTs Arrays with Abundant Defects and Interfaces for Alkaline Water Splitting

“…Moreover, the new peaks detected at 233.5 and 230.5 eV correspond to Mo 5+ 2p 3/2 and Mo 5+ 2p 5/2 , respectively, while the peaks detected at 232.2 and 229.2 eV can be assigned to Mo 4+ 2p 3/2 and Mo 4+ 2p 5/2 , respectively, verifying the partial reduction of the Mo species and change of the chemical coordination environment of Mo atoms. , In the Ni 2p spectrum, the peaks at 873.8 and 856.0 eV are in line with Ni 2+ 2p 1/2 and Ni 2+ 2p 3/2 , respectively (Figure f). With the partial reduction of the Ni species, the peak pairs centered at 870.3/853.4 and 868.0/852.0 eV can be assigned to Ni(1) and Ni(0), respectively. , Similarly, the peak pairs centered at 726.0/713.0, 724.6/711.0, and 719.8/707.8 eV in the Fe 2p spectrum (Figure g) can be ascribed to Fe 3+ , Fe 2+ , and Fe(0), respectively, indicating the partial reduction of Fe 3+ to Fe 2+ and Fe(0). , The change of the chemical coordination environment of the Mo, Ni, and Fe atoms may adjust the electronic structure and then boost the electrocatalytic capability of the composites.…”

“…54,55 Similarly, the peak pairs centered at 726.0/ 713.0, 724.6/711.0, and 719.8/707.8 eV in the Fe 2p spectrum (Figure 4g) can be ascribed to Fe 3+ , Fe 2+ , and Fe(0), respectively, indicating the partial reduction of Fe 3+ to Fe 2+ and Fe(0). 44,56 The change of the chemical coordination environment of the Mo, Ni, and Fe atoms may adjust the electronic structure and then boost the electrocatalytic capability of the composites.…”

Multielectron Electrode Reaction Kinetics with RDE and RRDE: An Advanced Electrochemical Laboratory Experiment

“…Thus, the limiting current density of ORR occurs in the high overpotential region. From Figure B, the onset potential, half-wave potential and the limiting current density of LSV is 0.9 V, 0.8 V (vs RHE), and 5.7 mA/cm 2 , respectively. It is common knowledge that the higher the onset potential and the half wave potential, the better the catalytic activity of ORR catalyst. , The Pt/C catalyst displays high onset potential and half-wave potential, suggesting good electrocatalytic activity. Therefore, the catalytic activity of the Pt/C electrode can be evaluated by LSV curve. …”

“…It is common knowledge that the higher the onset potential and the half wave potential, the better the catalytic activity of ORR catalyst. 18,19 The Pt/C catalyst displays high onset potential and half-wave potential, suggesting good electrocatalytic activity. Therefore, the catalytic activity of the Pt/C electrode can be evaluated by LSV curve.…”