Incorporation of new functional components into a three-dimensional graphene (3DG) framework improves the performance of supercapacitors based on 3DG as electrodes by tailoring the framework’s structure and properties. In this work, graphene quantum dots (GQDs) were incorporated into 3DG via one-step hydrothermal treatment of GQDs and graphene oxide (GO). By simply adjusting the GQDs/GO feeding ratio by weight, various GQDs/3DG composites were formed. The maximum feeding ratio was 80%, and the prepared composites possessed saturated GQDs loading on the 3DG framework, whereas composites obtained with a GQDs/GO feeding ratio of 40% as electrodes exhibited optimal specific capacitance of 242 F·g⁻¹ for supercapacitors, an increase of 22% compared with that of pure 3DG electrodes (198 F·g⁻¹). This improved performance was mainly due to better electrical conductivity and larger surface area for GQDs/3DG composites with moderate GQDs content. The fabricated GQDs/3DG composites as electrodes for supercapacitors revealed high electrochemical stability. Their capacitance kept 93% of the initial value after 10,000 charge-discharge cycles.

Silver sulfide, cadmium sulfide and nickel (Ag₂S/CdS/Ni) ternary nanostructures were fabricated by a two step process and characterized by x-ray powder diffraction, transmission electron microscopy, and UV–vis diffuse reflection spectroscopy. The photocatalytic hydrogen production activity of ternary nanostructures and reference samples were evaluated using triethanolamine (TEOA) as sacrificial reagent in water under visible-light illumination (λ ≥ 420 nm). The result shows Ag₂S/CdS/Ni nanostructures exhibited a high visible light photocatalytic H₂ evolution rate of 1.54 mmolh⁻¹ g⁻¹, which was 4.6 times and 1.4 times higher than that of 1.2% mol Ag₂S/CdS and Ni/CdS. The degree of photocorrosion of CdS were employed to study the photogenerated carriers transfer route by measuring and comparing the concentration of Cd²⁺ in the solution of the photocorrosion experiments in a nonsacrificial system. A long-range electric field, which is similar to the p-i-n electric field structure, was proposed to be constructed by Ni nanoparticles and Ag₂S nanoparticles in CdS. Most of the photogenerated electrons and holes in CdS drift to the electron donor and electron acceptor respectively under the action of long-range electric field, which greatly improves the separation efficiency of photogenerated carriers and the photocatalytic H₂ production activity.

0.3 mol% platinum loaded g-C₃N₄ sample was prepared by photoreduction method to study the long-term stability of photocatalysts. For the first time, we have discovered the oriented attachment (OA) mechanism growth of Pt nanoparticles on g-C₃N₄ solid surface, which is completely different from Ostwald ripening (OR) or particle migration and coalescence (PMC) that previously reported. The Pt nanoparticles perform Brownian motion on the surface of g-C₃N₄ support under the collision of liquid molecules, then two or more nanoparticles attach together via the crystallographic orientation to construct larger ones. Al₂O₃ film prepared by atomic layer depositon was introduced to inhibit the Brownian motion of Pt nanoparticles. It is found that as the increase of the Al₂O₃ growth cycles, the photocatalytic hydrogen production of Pt/g-C₃N₄ coated by Al₂O₃ increase from 1.14 mmolg⁻¹h⁻¹ to 2.08 mmolg⁻¹h⁻¹ and then decrease to 1.4 mmolg⁻¹h⁻¹, and the apparent quantum efficiency (QE) also increase from 1.2% to 2.1% and then decrease to 1.4%. Meanwhile, the long-term stability of photocatalyst always increases. This work has revealed new pathway of photocatalytic nanoparticle growth on solid surface and proposed the method to prevent it.