A schematic diagram showing the synthesis of the 1T-MoS₂/Ti₃C₂T_x heterostructure and the fast charge–discharge networks in the heterostructure.

Electrocatalytic water splitting is an efficient route to generate renewable energy sources, in which the noble metal materials are usually used as electrocatalysts. But the high price and scarcity of these catalysts impede their large-scale applications. Ni-based materials are considered to be the most suitable catalytic materials to substitute these noble metal materials. In this paper, the monodispersed α-Ni(OH)₂ microspheres assembled by ultrathin nanosheets were synthesized by a facile solvothermal method. This method was surfactant-free and no precipitator was used. The as-obtained products were well-characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), thermal gravimetric (TG) analysis, and X-ray photoelectron spectroscopy (XPS). The results of N₂ adsorption/desorption isotherm indicate that the BET surface area of the products was 169.94 m²g⁻¹, and the pore-size distribution centered at 3.5 nm. Then, the electrochemical properties were evaluated by linear sweep voltammetry (LSV) in 1 M KOH. At a current density of 10 mA cm², the overpotential for the α-Ni(OH)₂-MS is 320 mV, and the Tafel slope is 98.7 mV dec⁻¹, indicating its excellent reaction kinetics for an efficient catalyst toward oxygen evolution reaction (OER).

Cobalt oxides are economical and environmentally friendly electrocatalysts and they may be possible alternatives to noble metals for the oxygen evolution reaction. However, the most studied intrinsic cobalt oxides still need a high overpotential to overcome the current density threshold of oxygen evolution and are unstable for continuous reactions. Herein, we found that the catalytic activity of cobalt oxides improved significantly on soaking them in a weakly acidic iron–ion solution. The structure of the catalyst could be modified by the abovementioned treatment to reduce the overpotential, thus achieving improved catalytic efficiency for the oxygen evolution reaction. The formation of Fe-Co₃O₄ delivered a much lower overpotential of 280 mV at 10 mA cm⁻² (with a small Tafel slope of 55 mV dec⁻¹) compared with normal Co₃O₄ (409 mV) for the OER; additionally, Fe-CoO also exhibited a lower overpotential of 296 mV compared with normal CoO (361 mV). The activity of the Fe ion-treated cobalt oxides was promoted by a thousand CV scans, which might form an amorphous phase layer. Density functional theory (DFT) calculations also indicated that the theoretical overpotentials of Fe-Co₃O₄ and Fe-CoO were obviously lower than that of the untreated material. The treated cobalt oxides replaced cobalt atoms with a certain number of iron atoms, which dramatically changed the electronic structure and charge transfer rate.

A schematic diagram showing that the interlayer spacing of MoS₂is expanded through tetrahedral TBAB or linear CTAB intercalation. The migration energy barrier of Na between the MoS₂layer and CTAB molecules is significantly reduced than that of TBAB.

MCo₂O₄ (M = Mn,Ni) microparticles were synthesised by a simple hydrothermal solvothermal method. The samples were characterised by X-ray diffraction, X-ray energy dispersive spectroscopy and scanning electron microscopy, which showed that MnCo₂O₄ microparticles with spherical particles aggregated by a large number of small cubes and cubic shaped NiCo₂O₄ microcubes were obtained. The microwave absorption properties of these products were systematically investigated by vector network analysis. Results indicated that the minimum reflection loss value of MnCo₂O₄ microparticles was −26.34 dB at 11.04 GHz with the absorber thickness of 2.5 mm, which was much lower than that of NiCo₂O₄ microcubes with the same absorber thickness. The possible mechanism was analysed, indicating that the geometry and size of MCo₂O₄ (M = Mn,Ni) microparticles played a key role in microwave absorption.