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Multinary selenides, Sn 4 In 5 Sb 9 Se 25 (1) and Sn 6.13 Pb 1.87 In 5.00 Sb 10.12 Bi 2.88 Se 35 (2) were synthesized by solid-state sintering reactions. These compounds were initially observed resulting from the exploratory synthesis of multinary selenides in In–Sn–Sb–Se systems. Sn 4 In 5 Sb 9 Se 25 crystallizes in a monoclinic lattice with a ​= ​31.820(2) Å, b ​= ​4.0241(3) Å, c ​= ​19.703(2) Å, β ​= ​114.246(5)°, and V ​= ​2300.4(3) Å3; space group C2/m (No. 12); Z ​= ​2. Sn 6.13 Pb 1.87 In 5.00 Sb 10.12 Bi 2.88 Se 35 crystallizes in a monoclinic lattice with a ​= ​31.6883(5) Å, b ​= ​4.0709(1) Å, c ​= ​26.5406(4) Å, β ​= ​105.710(1)°, and V ​= ​3295.8(2) Å3; C2/m (No. 12); Z ​= ​2. The structures of both compounds are constructed with two building units of NaCl100-type [ M 2 x − 4 2 + M 4 3 + Se 2 x + 2 ] ∞ 1 and NaCl111-type [ M 2 y − 2 3 + Se 3 y − 3 ] ∞ 2. The structural anisotropy leads to a columnar or layered shape and strongly preferred orientation along [010] direction upon two compounds. These materials exhibit black color comprising a semiconducting property. Band gaps observed in electrical conductivity measurements are 0.66 ​eV and 0.62 ​eV for compound 1 and 2 , respectively. UV–vis–NIR spectroscopy and the electronic band structure calculations at the density functional theory (DFT) level indicate the results of the semiconducting behaviors. Measurements of Seebeck coefficient indicates p-type semiconductors for both compounds. New multinary chalcogenides: Sn 4 In 5 Sb 9 Se 25 and Sn 6.13 Pb 1.87 In 5.00 Sb 10.12 Bi 2.88 Se 35 , with complex crystal structures have been successfully synthesized via a combination of single-crystal X-ray diffraction and tuning chemical composition. Their physical properties are reported herein. Both materials consist of similar units and imply a new homologous series. [Display omitted] • New multinary chalcogenides: Sn 4 In 5 Sb 9 Se 25 and Sn 6.13 Pb 1.87 In 5.00 Sb 10.12 Bi 2.88 Se 35 have been successfully synthesized. • Both materials contain similar building units with different sizes. • Electronic band structure calculations are studied and indicate semiconducting behaviors for both compounds. [ABSTRACT FROM AUTHOR]

PbO 2 , PbO 2 /Pb 3 O 4 composite, and Pb 3 O 4 were synthesized respectively via the simple hydrothermal method under different reaction durations (3–48 ​h). All the prepared samples were used as anode materials to decontaminate methyl orange (MO) to explore the corresponding electrochemical advanced oxidation performance. The detailed experimental designs suggested that the combination of PbO 2 and Pb 3 O 4 offered enhanced electrochemical advanced oxidation performance, which was due to possible synergistic effects. XPS results suggest that the content of adsorbed oxygen species (O ads) is obviously higher in PbO 2 /Pb 3 O 4 composite. It is very likely due to more oxygen vacancies in the crystal structure of PbO 2 /Pb 3 O 4 composite, which will adsorb more oxygen species, promote charge transfer and provide more electrochemical active surface area to generate oxidizing agents. Besides, the presence of Pb 3 O 4 can suppress the oxygen evolution and improve the accelerated life. Meanwhile, the effects of current density, catalyst loading amount and initial MO concentration on electro-catalysis degradation of MO were explored. Experimental results suggested that MO removal efficiency was 94.3%, the reaction kinetic constant could reach 2.08 ⅹ 10-2 min-1, and COD removal efficiency was 34.2% after 150 ​min of reaction under optimized conditions: current density was 5 ​mA ​cm-2, catalyst loading amount was 1 ​mg ​cm-2 and initial MO concentration was 50 ​mg ​L-1. Furthermore, possible degradation mechanisms of MO was proposed according to the analyzed results obtained from UV–Vis and HPLC-MS. Relative ratio of PbO 2 and Pb 3 O 4 can be altered by changing the hydrothermal reactions durations, and PbO 2 /Pb 3 O 4 composite exhibited enhanced electrochemical advanced oxidation performance. [Display omitted] • Ratio of PbO 2 and Pb 3 O 4 can be adjusted by hydrothermal reaction durations. • PbO 2 /Pb 3 O 4 composite displayed enhanced electro-catalytic performance. • Role of different operating conditions was investigated. • Degradation byproducts of MO were identified and the possible pathways were proposed. [ABSTRACT FROM AUTHOR]