The study of high-performance electrocatalysts for driving the oxygen evolution reaction (OER) is important for energy storage and conversion systems. As a representative of inverse-spinel-structured oxide catalysts, nickel ferrite (NiFe 2 O 4 ) has recently gained interest because of its earth abundance and environmental friendliness. However, the gained electrocatalytic performance of NiFe 2 O 4 for the OER is still far from the state-of-the-art requirements because of its poor reactivity and finite number of surface active sites. Here, we prepared a series of atomically thin NiFe 2 O 4 catalysts with different lateral sizes through a mild and controllable method. We found that the atomically thin NiFe 2 O 4 quantum dots (AT NiFe 2 O 4 QDs) show the highest OER performance with a current density of 10 mA cm −2 at a low overpotential of 262 mV and a small Tafel slope of 37 mV decade −1 . The outstanding OER performance of AT NiFe 2 O 4 QDs is even comparable to that of commercial RuO 2 catalyst, which can be attributed to its high reactivity and the high fraction of active edge sites resulting from the synergetic effect between the atomically thin thickness and the small lateral size of the atomically thin quantum dot (AT QD) structural motif. The experimental results reveal a negative correlation between lateral size and OER performance in alkaline media. Specifically speaking, the number of low-coordinated oxygen atoms increases with decreasing lateral size, and this leads to significantly more oxygen vacancies that can lower the adsorption energy of H 2 O, increasing the catalytic OER efficiency of AT NiFe 2 O 4 QDs.

A polyaniline-multiwalled carbon nanotube supported, high performance CoFe2O4 nanoparticle loaded electrocatalyst is synthesized through a novel and simple in situ process under mild conditions.

Electrocatalytic nitrogen reduction reaction (NRR) represents a highly promising process to ammonia synthesis for artificial N2 fixation. However, the yield rate for NH3 production and Faradaic efficiency (FE) are still low, which greatly hinder its widespread applications. Until now, although a variety of catalysts, including single-atom catalysts, have been developed for NRR in the pursuit of suppressing hydrogen evolution reaction (HER) and the corresponding higher FE, the limited NH3 yield rate makes them uncompetitive for the synthesis of ammonia. Herein, we report a Fe single-atom catalyst anchoring on a nitrogen-doped carbon substrate (Fe SAC/N–C) as a highly efficient NRR catalyst. The catalyst achieves a high FE of 39.6% in 0.1 M KOH under room temperature, particularly a dramatically enhanced NH3 yield rate of 53.12 μgNH3 h–1 mgcat –1. The isotopic labeling (15N2) experiment confirms that the NH3 production completely originates from N2 reduction. Meanwhile, theoretical calculations and X-ray fine structure analysis reveal that the Fe–N3 coordination of Fe SAC/N–C is indeed responsible for the suppression of HER, particularly resulting in a maximum activation of NRR intermediates to produce ammonia with a high yield rate.

A high-performance Ni 1Àx Fe x on polyethyleneimine (PEI)-functionalized molybdenum disulfide (MoS 2 ) electrocatalyst has been synthesized by an electroplating in situ growth approach. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the successful functionalization of MoS 2 with PEI. The empty orbitals of Ni 2+ and Fe 2+ (Ni and Fe precursors) coordinated with the donated lone pairs of nitrogen atoms in PEI-mediated MoS 2 and then the Ni 2+ and Fe 2+ were in situ reduced at a negative potential. Transmission electron microscope images and X-ray diffraction reveal that Ni 85 Fe 15 nanoparticles with an average size of 2.25 nm are uniformly dispersed on the PEI-MoS 2 sheets. The Ni 1Àx Fe x /PEI-MoS 2 catalyst exhibits unexpectedly high activity towards the hydrazine oxidation reaction, which can be attributed to highly homogeneous dispersed Ni 1Àx Fe x alloy. It also shows enhanced electrochemical stability due to the structural integrity of PEI-MoS 2 . Finally, the Ni 85 Fe 15 /PEI-MoS 2 catalyst is proved to be very valuable for applications in hydrazine fuel cells, as compared with Ni 90 Fe 10 / PANi-MoS 2 and Ni 85 Fe 15 /MoS 2 catalysts.

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A simple method is devised for the in situ growth of Ni-Fe alloy on graphene-like MoS 2 . The Ni-Fe/MoS 2 hybrid with a Ni:Fe molar ratio of 80 : 20 exhibits the highest electrocatalytic activity toward hydrazine oxidation. The electrocatalytic activity is remarkably enhanced by the synergistic effects between graphene-like MoS 2 and Ni-Fe alloy.