The 3D NiO hollow sphere/reduced graphene oxide (rGO) composite was synthesized according to the coordinating etching and precipitating process by using Cu₂O nanosphere/graphene oxide (GO) composite as template. The morphology, structure, and composition of the materials were characterized by SEM, TEM, HRTEM, XPS, and Raman spectra, and the electrochemical properties were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry. Moreover, the electrochemical activity of the composite materials with different morphologies were also investigated, which indicating a better combination of the NiO hollow sphere and the rGO. Used as glucose sensing material, the 3D NiO hollow sphere/rGO composite modified electrode exhibits high sensitivity of ~2.04 mA mM⁻¹ cm⁻², quick response time of less than 5 s, good stability, selectivity, and reproducibility. Its application for the detection of glucose in human blood serum sample shows acceptable recovery and R.S.D. values. The outstanding glucose sensing performance should be attributed to the unique 3D hierarchical porous superstructure of the composite, especially for its enhanced electron-transfer kinetic properties.

Solar steam generation has emerged as a promising and sustainable method of addressing the water shortage issue. Although various materials and structures have been reported, designing a highly efficient steam generation device with excellent salt resistant performance remains a great challenge. For the first time, a polypyrrole (PPy)–wood device has been prepared through a simple “soak and polymerization” process by in situ polymerization of pyrrole monomers into a three-dimensional (3D) porous wood matrix. The PPy particles decorated on the wood matrix can convert incident light into heat while the 3D porous wood matrix can further enhance light absorption based on light harvesting and multiple scattering effects, which allows the PPy–wood light absorption to reach as high as 97.5% in the spectral range from 250 nm to 2500 nm. Owing to the low thermal conductivity of wood, the PPy–wood can localize the converted heat at the surface of the device, enabling efficient steam generation. The hydrophilicity and the numerous aligned microchannels of the PPy–wood ensure constant water supply to the air–water interface. All these merits endow the PPy–wood with a high solar energy conversion efficiency of 83% under 1 Sun, with an evaporation rate of 1.33 kg m⁻² h⁻¹. Moreover, the fabricated PPy–wood also shows good structure stability and cycling stability as well as excellent salt resistant performance. Benefiting from the low-cost of wood and the simple fabrication process, the PPy–wood with the above merits is one of the most suitable candidates for solar desalination.

Electrochemical water splitting requires an efficient water oxidation catalyst to accelerate the oxygen evolution reaction (OER). A triple hierarchy catalyst structure based on abundant transition metals in soil (Fe, Co, and Ni) was prepared via chemical bath deposition, followed by a hydrothermal and electrodeposition method for the high-efficiency OER. The obtained electrode consisted of a three-layer porous structure, with a carbon cloth (CC) substrate as the bottom layer, vertically aligned Co₉S₈ nanotubes as the intermediate layer, and NiFe hydroxide as the top layer, resulting in two synergistic effects between Co₉S₈ and CC, and NiFe and Co₉S₈. This layered structure contained no binder, which facilitated catalytic site exposure, enhanced electron transfer, and accelerated the dissipation of gases generated during the catalytic process. This triple hierarchy multimetal/carbon electrode exhibited remarkable OER activity in an alkaline medium with a small overpotential of 219 mV (vs. RHE) at 10 mA·cm⁻² and low Tafel slope of 55 mV·dec⁻¹. Furthermore, this triple hierarchy electrode was stable for up to 20 h. The prepared triple hierarchy polymetallic material can be considered to be among the most promising oxygen evolution catalysts.

In this work, the hierarchical NiCo₂O₄ hollow sphere synthesized via a “coordinating etching and precipitating” process was demonstrated to exhibit intrinsic peroxidase-like activity. The peroxidase-like activity of NiCo₂O₄, NiO, and Co₃O₄ hollow spheres were comparatively studied by the catalytic oxidation reaction of 3,3,5,5-tetramethylbenzidine (TMB) in presence of H₂O₂, and a superior peroxidase-like activity of NiCo₂O₄ was confirmed by stronger absorbance at 652 nm. Furthermore, the proposed sensing platform showed commendable response to H₂O₂ with a linear range from 10 μM to 400 μM, and a detection limit of 0.21 μM. Cooperated with GOx, the developed novel colorimetric and visual glucose-sensing platform exhibited high selectivity, favorable reproducibility, satisfactory applicability, wide linear range (from 0.1 mM to 4.5 mM), and a low detection limit of 5.31 μM. In addition, the concentration-dependent color change would offer a better and handier way for detection of H₂O₂ and glucose by naked eye.

In this paper, Au and reduced graphene oxide (rGO) were successively deposited on fluorine-doped SnO₂ transparent conductive glass (FTO, 1 × 2 cm) via a facile and one-step electrodeposition method to form a clean interface and construct a three-dimensional network structure for the simultaneous detection of nitrite and hydrogen peroxide (H₂O₂). For nitrite detection, 3D Au-rGO/FTO displayed a sensitivity of 419 μA mM⁻¹ cm⁻² and a linear range from 0.0299 to 5.74 mM, while for the detection of H₂O₂, the sensitivity was 236 μA mM⁻¹ cm⁻² and a range from 0.179 to 10.5 mM. The combined results from scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction measurements (XRD) and electrochemical tests demonstrated that the properties of 3D Au-rGO/FTO were attributabled to the conductive network consisting of rGO and the good dispersion of Au nanoparticles (AuNPs) which can provide better electrochemical properties than other metal compounds, such as a larger electroactive surface area, more active sites, and a bigger catalytic rate constant.