Especially cellular aluminum materials have been extensively developed and investigated in the recent years. But also magnesium is a suitable metal for cellular metals due to its low density. By a special casting method open‐cellular magnesium with a very low density of 0.05 g/cm3 is fabricated that shows high potential for usage as energy absorbers.

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Photocatalytic water splitting is one of the ideal methods for solving the global energy crisis and its associated environmental problems. In this study, the effect of altering the molecular structure of porphyrins was investigated to improve the water splitting activity of Zr-doped KTaO 3 (KTa(Zr)O 3 ) modified with porphyrin dyes. UV-vis spectra indicated that porphyrins with long alkoxy chains tended to form well-developed H-aggregates on the KTa(Zr)O 3 surface. The photocatalytic activity of Pt-loaded KTa(Zr)O 3 was improved by using porphyrins with longer alkoxy chains because of the improvement in the charge migration between porphyrin dye molecules. While the charge transfer between the inorganic semiconductor and porphyrin dye interface is important, it was found that the formation of H-aggregation was more effective in improving the water splitting activity of the porphyrin-modified photocatalysts.

The modification effect of acene dyes such as 6,13-bis­(triisopropylsilylethynyl)­pentacene (TIPS-PEN) and difuranoanthracene derivatives on the photocatalytic water splitting activity of Pt-loaded KTa­(Zr)­O3 was studied. The surface modification of KTa­(Zr)­O3 powder with acene dyes was conducted with an evaporation-to-dryness method using pyridine as a solvent. TIPS-PEN is the most effective dye for increasing the hydrogen formation rate on the KTa­(Zr)­O3 catalyst, which became larger by 14 times. The fluorescence spectrum of the TIPS-PEN-modified catalyst revealed that the excitation energy of KTa­(Zr)­O3 was transferred to the Pt cocatalyst through the TIPS-PEN moiety. The wavelength dependence of the photocatalytic activity was investigated, and the water splitting activity was improved by irradiating with both ultraviolet and visible light comparing with the case of irradiating with only ultraviolet light. Furthermore, the water splitting reaction did not occur under visible light irradiation, which suggests that a Z-scheme-type water splitting reaction, that is, a two-step photoexcitation mechanism similar to that occuring in plant photosynthesis, proceeded on PtO X /TIPS-PEN/KTa­(Zr)­O3.