2 Search Results

Hydrogen production from photoelectrochemical (PEC) water splitting using semiconductor photocatalysts has attracted great attention to realize clean and renewable energy from solar energy. The visible light response of WO₃ with a long hole diffusion length (~150 nm) and good electron mobility (~12 cm² V^–1 s^–1) makes it suitable as the photoanode. Yet, WO₃ suffers from issues including rapid recombination of photoexcited electron–hole pairs, photo-corrosion during the photocatalytic process due to the formation of peroxo-species, sluggish kinetics of photogenerated holes, and slow charge transfer at the semiconductor/electrolyte interface. Our report highlights the approaches to overcome these drawbacks of WO₃ photoanodes, including:more » (i) the manipulation of nanostructured WO₃ photoanodes to decrease the nanoparticle size to promote hole migration to the WO₃/electrolyte interface which benefits the charge separation; (ii) doping or introducing oxygen vacancies to improve electrical conductivity; exposing high energy crystal surfaces to promote the consumption of photogenerated holes on the high-active crystal face, thereby suppressing the recombination of photogenerated electrons and holes; (iii) decorating with co-catalysts to reduce the overpotential which inhibits the formation of peroxo-species; (iv) other methods such as coupling with narrow band semiconductors to accelerate the charge separation and controlling the crystal phase via annealing to reduce defects. These methods are reviewed with detailed examples.« less

High absorption capacity and broad absorption bandwidth electromagnetic wave (EMW) absorption materials (namely, EMW absorbers) are highly desirable due to the interference with electronics and harms on human beings’ health. In search for rational design on nanostructured absorbers, we have synthesized and demonstrated the rod-shape composites with Fe-containing magnetic nanoparticles (Fe₃O₄, Fe₃C and Fe NPs) embedded into nano-porous carbon (NPC) through pyrolysis of Fe-based metal-organic frameworks (MOFs). The morphologies, compositions, and graphitization degree of the Fe-MOFs derived magnetic NPC nanorods can be effectively controlled via adjusting the pyrolysis temperatures. The graphitization level has a significant influence on the permittivity ofmore » the composites upon variation of pyrolysis temperatures, thereby a tunable electromagnetic wave (EMW) absorption is observed. Consequently, the resulting magnetic NPC nanorods obtained at pyrolysis temperature of 600 and 700 °C exhibit the most remarkable EMW absorption performance with a strong reflection loss of -52.9 dB and broad effective bandwidth (f_e) of 4.64 GHz at 3.07 mm. With a thickness of 3.5 mm, the f_e for the magnetic NPC nanorods at 600 °C covers the whole X-band from 7.92 to 12.48 GHz. Finally, the noticeable EMW absorption performances have been greatly enhanced compared to those reported Fe₃O₄ based absorbers, owing to the synergy of multiple components and the porous structures inherited from MOFs.« less