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Ultra-fast covalent grafting of PPD-PMo₁₂ on rGO (PPD-PMo₁₂@rGO) leads to a covalently linked dual network structure that enhances supercapacitor performance.

The simple and cost-efficient preparation of high-performance nitrogen-doped carbon aerogel (N-CA) for supercapacitors and other applications is still a big challenge. In this work, we have presented a facile strategy to synthesize hierarchically porous N-CA, which is based on solvothermal polymerization of phenol and formaldehyde under hypersaline condition with ethylenediamine (EDA) functioning as both a catalyst and a nitrogen precursor. Benefited from the catalytic effect of EDA on the polymerization, the obtained N-CA has a predominant amount of micropores (micropore ratio: 52%) with large specific surface area (1201.1 m2·g−1). In addition, nitrogen doping brings N-CA enhanced wettability and reduced electrochemical impedance. Therefore, the N-CA electrode shows high specific capacitance (426 F·g−1 at 1 A·g−1 in 0.5 M H2SO4) and excellent cycling stability (104% capacitance retention after 10,000 cycles) in three-electrode systems. Besides, a high energy density of 32.42 Wh·kg−1 at 800 W·kg−1 can be achieved by symmetric supercapacitor based on the N-CA electrodes, showing its promising application for energy storage. Furthermore, N-CA also exhibits good capacity and long recyclability in the absorption of organic solvents.

By using titanyl sulfate and ammonia metatungstate (AMT) as precursors and citric acid as a complexing agent, mesoporous hollow spheres of TiO 2 /WO 3 composites were prepared via a two-step approach, which included a spray-drying process followed by a high-temperature calcination course. The morphologies, microstructures, surface area, crystal phase, and optical properties of the composites were characterized by SEM, TEM, BET, XRD and UV-Vis DRS. The results showed that the TiO 2 /WO 3 composites were well-dispersed mesoporous hollow spheres with diameters around 1 μm, of which the wall consisted of nanoparticles and mesopores. What's more, nanoparticles and mesopores increased with the calcination temperature. UV-Vis DRS analysis showed that the absorption spectra of TiO 2 /WO 3 composites could extend from ultraviolet region to visible region, which was helpful to improve the utilization efficiency of sunlight. In addition, photocatalytic activities of the prepared samples were investigated by photo-degradation of methylene blue (MB). It's found that the composite containing 3% molar ratio of WO 3 with calcination temperature of 500 o C showed the best photocatalytic activity. The degradation efficiency of MB with this composite could reach 99.1%, much higher than that of P25, which was only 29.5% under the same conditions.

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