RbEu(MoO4)2 is synthesized by the two-step solid state reaction method. The crystal structure of RbEu(MoO4)2 is defined by Rietveld analysis in space group Pbcn with cell parameters a=5.13502(5), b=18.8581(2) and c=8.12849(7) Å, V=787.13(1) Å 3 , Z=4 (RB=0.86%). This molybdate possesses its phase transition at 817 K and melts at 1250K. The Raman spectra were measured with the excitation at =1064 and 514.5nm. The photoluminescence spectrum is evaluated under the excitation at 514.5nm. The absolute domination of hypersensitive 5 D0→ 7 F2 transition is observed. The ultranarrow 5 D0→ 7 F0 transition in RbEu(MoO4)2 is positioned at 580.2nm being 0.2nm blue shifted, with respect to that in Eu2(MoO4)3.

The systematic study of the platinum speciation in sulfuric acid solutions of platinum (IV) hydroxide { [Pt-(OH) 4 (H 2 O) 2 ], HHPA} was performed with the use of a combination of methods. Depending on the prevailing Pt form, the three regions of H 2 SO 4 concentration were marked: (1) up to 3 M H 2 SO 4 forms unstable solutions gradually generating the PtO 2 • xH 2 O particles; (2) 4−12 M H 2 SO 4 , where the series of mononuclear aqua−sulfato complexes ([Pt(SO 4 ) n (H 2 O) 6−n ] 4−2n , where n = 0•••4) dominate; and (3) 12 M and above, where, along with [Pt(SO 4 ) n (H 2 O) 6−n ] 4−2n species, the polynuclear Pt(IV) species and complexes with a bidentate coordination mode of the sulfato ligand are formed. For the first time, the salts of the aqua−hydroxo Pt(IV) cation [Pt(OH) 2 (H 2 O) 4 ]SO 4 (triclinic and monoclinic phases) were isolated and studied with a combination of methods, including the single-crystal X-ray diffraction. The formation of PtO 2 •xH 2 O particles in sulfuric acid solutions (1−3 M) of HHPA and their spectral characteristics and morphology were studied. The deposition of PtO 2 •xH 2 O was highlighted as a convenient method to prepare various Pt-containing heterogeneous catalysts. This possibility was illustrated by the preparation of Pt/g-C 3 N 4 catalysts, which show an excellent performance in catalytic H 2 generation under visible light irradiation with a quantum efficiency up to 5% and a rate of H 2 evolution up to 6.2 mol•h −1 per gram of loaded platinum.

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