Spinel Nickel Ferrite Nanoparticles Supported on a 1T/2H Mixed-Phase MoS₂ Heterostructured Composite as a Bifunctional Electrocatalyst for Oxygen Evolution and Oxygen Reduction Reactions

Abstract

A composite electrocatalyst of NiFe2O4 supported on a 2H/1T multiphase MoS2 nanosheet is reported. The as-prepared NiFe2O4/MoS2 heterostructured composite exhibited an excellent bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. The composite electrocatalyst exhibited an OER current density of 10 mA cm–2 with an overpotential of 330 mV in 1 M KOH comparable to that of IrO2. On the other hand, the composite electrocatalyst exhibited an ORR onset potential (E onset) of 0.82 V vs RHE. The K–L plot and rotating ring-disk electrode analysis evidenced that the ORR on the NiFe2O4/MoS2 heterostructure follows closely the 4 e– transfer process similar to Pt/C and delivered notable electrochemical stability after 5000 potential cycles with retention of about 90% diffusion-limiting current density. The H2–O2 anion exchange membrane fuel cell (AEMFC) employing the cathode electrode fabricated with the NiFe2O4/MoS2 composite showed a peak power density of ∼20 mW cm–2. In contrast, a peak power density of ∼51 mW cm–2 was realized for the AEMFC employing the Pt/C cathode electrode under identical operating conditions. Considering the excellent bifunctional activity, good electrochemical performance and stability, and the low-cost facile synthetic approach, the NiFe2O4/MoS2 heterostructured composite developed in this study can be considered as a potential candidate for energy conversion and storage applications.

Influence of Exfoliated Boron Nitride for Fabrication of a Lightweight Wideband Microwave Absorbing Material

“…Figure4edepicts the deconvoluted XPS spectra of Fe. The presence of two peaks at ∼708.5 and ∼721.7 eV confirms the Fe 3+ state of iron in NiFe 2 O 4 52,53. Moreover, the deconvoluted XPS spectra of Fe show two satellite peaks at ∼716.1 and ∼729.9 eV (Figure4e).…”

“…The fitted Ni 2p core-level spectrum shows two satellite peaks and the two spin–orbit doublet peaks (Figure d). The peaks at ∼852.3 and ∼870 eV corresponding to the Ni 2p3/2 and Ni 2p1/2, respectively, indicate the presence of Ni 2+ in 15-NiFBN. , Figure e depicts the deconvoluted XPS spectra of Fe. The presence of two peaks at ∼708.5 and ∼721.7 eV confirms the Fe 3+ state of iron in NiFe 2 O 4 . , Moreover, the deconvoluted XPS spectra of Fe show two satellite peaks at ∼716.1 and ∼729.9 eV (Figure e).…”

“…The peaks at ∼852.3 and ∼870 eV corresponding to the Ni 2p3/2 and Ni 2p1/2, respectively, indicate the presence of Ni 2+ in 15-NiFBN. , Figure e depicts the deconvoluted XPS spectra of Fe. The presence of two peaks at ∼708.5 and ∼721.7 eV confirms the Fe 3+ state of iron in NiFe 2 O 4 . , Moreover, the deconvoluted XPS spectra of Fe show two satellite peaks at ∼716.1 and ∼729.9 eV (Figure e). Additionally, the 15-NiFBNs O 1s spectrum is deconvoluted into three peaks at ∼527.4, ∼529.1, and ∼530.6 eV, caused by the strong metal–oxygen bonds, O–H and O–B in the NiFe 2 O 4 nanostructure, respectively (Figure f). , …”

“…3 and ∼870 eV corresponding to the Ni 2p3/2 and Ni 2p1/2, respectively, indicate the presence of Ni 2+ in 15-NiFBN 48,52. Figure4edepicts the deconvoluted XPS spectra of Fe.…”

Sodium Tartrate-Assisted Synthesis of High-Purity NiFe2O4 Nano-Microrods Supported by Porous Ketjenblack Carbon for Efficient Alkaline Oxygen Evolution

“…More profoundly, the introduction of cheap and commercially available KB during the synthesis of NiFe 2 O 4 /KB and CoFe 2 O 4 /KB produced catalysts with much higher OER activities compared with the corresponding ferrite counterparts (NiFe 2 O 4 and CoFe 2 O 4 ). The η 10 value of 258 mV (vs RHE) measured for NiFe 2 O 4 /KB is one of the smallest values yet reported for ferrite-based electrocatalysts during OER (Table S1), − ,,,,,,− outperforming NiFe 2 O 4 /carbon cloth (340 mV vs RHE), NiFe 2 O 4 /FeNi 3 foam (262 mV vs RHE), NiFe 2 O 4 /Ti 3 C 2 (266 mV vs RHE), NiFe 2 O 4 /Ni@C (330 mV vs RHE), NiFe 2 O 4 -hollow nanoparticles/CNTs (260 mV vs RHE), and NiFe 2 O 4 /rGO (302 mV vs RHE) . Few ferrite-based composite catalysts have been reported with η 10 values lower than NiFe 2 O 4 /KB, though most have complicated compositions and cumbersome preparation routes, such as phosphided NiFe/NiFe 2 O 4 embedded into porous N-doped carbon nanospheres (P-FeNi/FeNiO/CNS, 220 mV vs RHE) or 3D porous CoFe 2 O 4 /C nanorod arrays supported on Ni foam@polyaniline (Ni foam@NC-CoFe 2 O 4 /C, 240 mV vs RHE) …”