A novel template-free approach to prepare nitrogen-doped hollow carbon microspheres with graphitic carbon shells (NHGCSs) was reported. The obtained NHGCSs by the direct pyrolysis of solid melamine–formaldehyde (MF) resin spheres exhibit excellent capacitance performance. The specific capacitance reaches 306 F g⁻¹ at a current density of 0.1 A g⁻¹ (in 2 M H₂SO₄), and remains as high as 230 F g⁻¹ even at a high current density of 3 A g⁻¹, which indicates the optimistic prospects for using NHGCSs as supercapacitor electrode materials.

NiO porous nanowall arrays have been successfully grown in situ on ceramic tubes by a hydrothermal reaction, combined with a calcination process. With such unique hierarchical pores, the array film sensor displayed excellent sensing performance toward H₂S.

Monodisperse vanadium pentoxide hollow spheres (VOHSs) were synthesized via a simple template-free solvothermal route followed by calcination in air. The as-prepared precursor and VOHSs were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron microscopy (XPS). Diameters of these VOHSs are in the range of 500–550 nm with a shell thickness of 55 nm. Building blocks of the hollow spheres are nanoplates with widths of 50–80 nm and lengths of 70–120 nm. The precursor hollow spheres gradually formed from solid spheres, to yolk–shell structures and to hollow spheres. Vanadium pentoxide based hollow sphere film sensors were fabricated via in situ solvothermal deposition and exhibited excellent sensing performances for triethylamine with an extra low detection limit of 10 ppb and good selectivity. The selectivity of the sensor might be due to the reduction of V⁵⁺ ions to V⁴⁺ ions when the VOHSs are exposed to triethylamine. The VOHSs are a potential candidate for trace triethylamine detection.

A rGO–Co ₃ O ₄ YSNC composite electrode exhibits much improved OER activity.