Hierarchically devising NiFeO H catalyst with surface Fe active sites for efficient oxygen evolution reaction

Regulable in-situ autoredox for anchoring synergistic Ni/NiO nanoparticles on reduced graphene oxide with boosted alkaline electrocatalytic oxygen evolution

To develop ideal alternatives to noble metal catalysts, transition metal catalysts supported on graphene have been receiving extensive attention in the field of electrochemical energy. In this work, using graphene oxide (GO) and nickel formate as precursors, Ni/NiO synergistic nanoparticles with regulable composition are anchored on reduced graphene oxide (RGO) to prepare Ni/NiO/RGO composite electrocatalysts through in-situ autoredox. Thanks to the synergistic effect of Ni³⁺ active sites and Ni electron donors, the as-prepared Ni/NiO/RGO catalysts exhibit efficient electrocatalytic oxygen evolution performance in 1.0 M KOH electrolyte. The optimal sample has an overpotential of only 275 mV at a current density of 10 mA cm^-2 and a small Tafel slope of 90 mV dec^-1, which are very comparable to those of commercial RuO₂ catalyst. Additionally, the catalytic capacity and structure remain stable after 2000 cyclic voltammetry cycles. For the electrolytic cell assembled with the best-performing sample as anode and commercial Pt/C as cathode, the current density can reach 10 mA cm^-2 at a low potential of 1.57 V and remains stable after 30 h of continuous work. It would be expected that the as-developed Ni/NiO/RGO catalyst with high activity should have broad application prospects.

Rapid Synthesis of Large-Size Fe2O3 Nanoparticle Decorated NiO Nanosheets via Electrochemical Exfoliation for Enhanced Oxygen Evolution Electrocatalysis

A novel nonprecious Fe₂O₃ nanoparticle decorated NiO nanosheet (Fe₂O₃ NPs@NiO NSs) composite has been obtained by a rapid one-pot electrochemical exfoliation method and can be used as an efficient oxygen evolution reaction (OER) catalyst. In the nanocomposite, the Fe₂O₃ NPs are uniformly anchored on the ultrathin graphene-like NiO nanosheets. At the same time, we also studied the influence of the Fe/Ni molar ratio on the morphology and catalytic activity. The Fe₂O₃ NPs@NiO NSs nanocomposite possessed a high BET surface area (194.1 m² g^-1), which is very conducive to the charge/mass transfer of electrolyte ions and O₂. Owing to the unique two-dimensional (2D) heterostructures and rational Fe content, the as-prepared Fe₂O₃ NPs@NiO NSs show high catalytic performance, a low overpotential at 10 mA cm^-2 (221 mV), a small Tafel slope (53.4 mV dec^-1), and 2000 cycle and 20 h long-term durability. The introduction of Fe₂O₃ NPs is beneficial to accelerating charge transport, increasing the electrochemically active surface area (ECSA), and thus improving the release of oxygen bubbles from the electrode surface.