Designing and preparing porous transition metal ferrites without using any template, shape-directing agent, and surfactant is a challenge. Herein, heterojunction MFe₂O₄ (M = Co, Ni, Cu, Mn) nanofiber (NF) based films with three-dimensional configurations were synthesized by electrospinning and the subsequent thermal treatment processes. Characterization results indeed show the 3D net-like textural structures of the electrospun spinel-type MFe₂O₄ NFs. In particular, the resulting MFe₂O₄ NFs have lengths up to several dozens of micrometers with an average diameter size of about 150 nm and possess abundant micro/meso/macropores on both the surface and within the films. The hierarchically porous structures and high surface areas of these MFe₂O₄ NFs (for example, the CoFe₂O₄ NFs possess a larger BET specific surface area (61.48 m² g⁻¹) than those of the CoFe₂O₄ NPs (5.93 m² g⁻¹)) can afford accessible transport channels for effectively decreasing the mass transport resistances, enhancing the electrical conductivity, and increasing the density and reactivity of the exposed catalytic active sites. All these advantages will be responsible for the better electrocatalytic performances of these MFe₂O₄ NFs compared with their structural isomers (i.e. the MFe₂O₄ NPs) for the oxygen evolution reaction (OER) and H₂O₂ reduction in alkaline solution. Meanwhile, both the OER and H₂O₂ reduction catalytic activities for these MFe₂O₄ NFs obey the order of CoFe₂O₄ NFs > CuFe₂O₄ NFs > NiFe₂O₄ NFs > MnFe₂O₄ NFs > Fe₂O₃ NFs. The CoFe₂O₄ NFs represent a new class of highly efficient non-noble-metal catalysts for both OER and H₂O₂ reduction/detection in alkaline media.

Herein, ruthenium (Ru) and iridium (Ir) are introduced to tailor the atomic and electronic structure of self-supported nickel-vanadium (NiV) layered double hydroxide to accelerate water splitting kinetics, and the origin of high hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities are analyzed at atomic level. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectroscopy studies reveal synergistic electronic interactions among Ni, V, and Ru (Ir) cations. Raman spectra and Fourier and wavelet transform analyses of the extended X-ray absorption fine structure indicate modulated local coordination environments around the Ni and V cations, and the existence of V vacancies. The Debye–Waller factor suggests a severely distorted octahedral V environment caused by the incorporation of Ru and Ir. Theoretical calculations further confirm that Ru or Ir doping could optimize the adsorption energy of intermediates in the Volmer and Heyrovsky steps for HER and accelerate the whole kinetic process for OER.

A cobalt-based MOF (Co-MOF) and macroporous carbon (MPC) composite has been synthesised for the first time using a one-step hydrothermal treatment of the Co-MOF precursor mixture and MPC. The carbon skeleton exhibited a restrictive effect on the growth of Co-MOF crystallites; thus, the sizes of the crystallites matched well with those of the macropores of the MPC matrix. The formation of the composite material was verified by detailed characterisation (i.e., X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, energy dispersive X-ray, and thermogravimetric analyses). The obtained nanosized and nanocrystalline Co-MOF composite with incorporated MPC exhibited greatly improved electrochemical activity. More importantly, this composite, which displays excellent electrocatalytic ability for the oxidation of hydrazine and the reduction of nitrobenzene, can be used as a good electrochemical sensing platform.

Here, we describe the synthesis of a novel interwoven NiS/NiS₂ structure with an amorphous interface accomplished by carrying out a one-step thermal decomposition of nickel sulfate and thiourea.