Yolk-shelled particles with tailored physical and chemical properties are attractive for electrochemical energy storage. Starting with metal acetate hydroxide with tetragonal prism-like shapes, yolk-shelled Ni–Co mixed oxide nanoprisms with tunable composition have been prepared by simple thermal annealing in air. It is found that the yolk-shelled structure is formed due to the fast thermally driven contraction process. With the favorable porous structure and composition, these yolk-shelled Ni–Co oxide particles manifest greatly enhanced electrochemical properties when evaluated as electrodes for both hybrid supercapacitors and lithium ion batteries. In particular, the resultant Ni_0.37Co oxide sample delivers very high specific capacitance of over 1000 F g⁻¹ at a current density of 10 A g⁻¹ with remarkably high capacitance retention of 98% after 15 000 cycles.

In response to the increasing concerns over energy and environmental sustainability, photocatalytic water-splitting technology has attracted broad attention for its application in directly converting solar energy to valuable hydrogen (H₂) energy. In this study, high-efficiency visible-light-driven photocatalytic H₂ production without the assistance of precious-metal cocatalysts was achieved on graphene–Zn_xCd_1−xS composites with controlled compositions. The graphene-Zn_xCd_1−xS composites were for the first time fabricated by a one-step hydrothermal method with thiourea as an organic S source. It was found that thiourea facilitates heterogeneous nucleation of Zn_xCd_1−xS and in situ growth of Zn_xCd_1−xS nanoparticles on graphene nanosheets. Such a scenario results in abundant and intimate interfacial contact between graphene and Zn_xCd_1−xS nanoparticles, efficient transfer of the photogenerated charge carriers, and enhanced photocatalytic activity for H₂ production. The highest H₂-production rate of 1.06 mmol h⁻¹ g⁻¹ was achieved on a graphene–Zn_0.5Cd_0.5S composite photocatalyst with a graphene content of 0.5 wt %, and the apparent quantum efficiency was 19.8 % at 420 nm. In comparison, the graphene–Zn_xCd_1−xS composite photocatalyst prepared by using an inorganic S source such as Na₂S exhibited much lower activity for photocatalytic H₂ production. In this case, homogeneous nucleation of Zn_xCd_1−xS becomes predominant and results in insufficient and loose contact with the graphene backbone through weak van der Waals forces and a large particle size. This study highlights the significance of the choice of S source in the design and fabrication of advanced graphene-based sulfide photocatalytic materials with enhanced activity for photocatalytic H₂ production.

Mesoporous ferrihydrite/SiO₂ composites were synthesized according to a water-in-oil microemulsion method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, nitrogen-adsorption/desorption, and by X-ray photoelectron spectroscopy. The as-prepared porous ferrihydrite/SiO₂ composites showed an excellent adsorption performance for formaldehyde (HCHO) removal from indoor air at ambient temperature. It was found that the aging time during the synthesis had a significant impact on the pore structure, surface area, and HCHO adsorption of these materials. The ferrihydrite/SiO₂ composite that was aged for 3 h in the presence of tetraethyl orthosilicate (TEOS) exhibited a relatively high HCHO adsorption capacity, as well as good recyclability, which was attributed to a relatively large BET surface area, optimal pore size, a suitable Si/Fe atomic ratio, and a synergistic effect between ferrihydrite and SiO₂. This work not only demonstrates that porous ferrihydrite/SiO₂ composites can act as an efficient adsorbent toward HCHO, but suggests a new route for the rational design of cost-effective and environmentally benign adsorbents with high performance for indoor air purification.