No abstract

No abstract

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.

No abstract

As the core of an electrocatalyst, the active site is critical to determine its catalytic performance in the hydrogen evolution reaction (HER). In this work, porous N-doped carbon-encapsulated CoP nanoparticles on both sides of graphene (CoP@ NC/GR) are derived from a bimetallic metal−organic framework (MOF)@graphene oxide composite. Through active site engineering by tailoring the environment around CoP and engineering the structure, the HER activity of CoP@NC/GR heterostructures is significantly enhanced. Both X-ray photoelectron spectroscopy (XPS) results and density functional theory (DFT) calculations manifest that the electronic structure of CoP can be modulated by the carbon matrix of NC/GR, resulting in electron redistribution and a reduction in the adsorption energy of hydrogen (ΔG H* ) from −0.53 to 0.04 eV. By engineering the sandwich-like structure, active sites in CoP@NC/GR are further increased by optimizing the Zn/Co ratio in the bimetallic MOF. Benefiting from this active site engineering, the CoP@NC/GR electrocatalyst exhibits small overpotentials of 105 mV in 0.5 M H 2 SO 4 (or 125 mV in 1 M KOH) to 10 mA cm −2 , accelerated HER kinetics with a low Tafel slope of 47.5 mV dec −1 , and remarkable structural and HER stability.