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New quaternary selenides M2Sb5Bi5Se17(M = Sn, Pb) were synthesized using solid‐state sintering reactions that crystallize in the monoclinic system with C2/m(No. 12) space group with lattice parameters a = 27.914(7) Å, b = 4.0804(11) Å, c = 15.512(4) Å, and β = 114.881(9)° for M = Sn, and a = 27.987(3) Å, b = 4.1062(5) Å, c = 15.6372(19) Å, and β = 115.318(3)° for M = Pb, respectively. The crystal structure is related to a homologous series [A+22x−4B+34Se−22x−2][B+32y−2Se−23y−3] with (x, y) = (3, 4) that contains building units of two‐dimensional slabs of NaCl111‐type [Sb2Bi4Se11] separated by 1D ribbons NaCl100‐type [Pb2Sb3BiSe6]. The NaCl111unit contains edge‐shared octahedra filled with Sb3+and Bi3+cations, which are parallel and overlapped to form a step‐layer 2D network stacking alone [001]. The NaCl100type ribbons containing Pb2+and Sb3+in square or trigonal pyramidal environments with the general formula [M6Se6] filled in the space between 2D layers of NaCl111units. The conductivity measurement revealed semiconducting property with band gaps of ~0.1 eV. Pb2Sb5Bi5Se17exhibits low thermal conductivity 3,000 μW cm−1K−1in a temperature range of 300–480 K. New quaternary selenides M2Sb5Bi5Se17(M = Pb/Sn) were synthesized and characterized. These are new members of a homologous series with the general formula [M2xSe2x+2][M2y−2Se3y−3] with a fixed ratio of metal cations. Pb2Bi5Sb5Se17exhibits semiconducting behaviors and low thermal conductivity.

Ternary chalcogenides, GeSb2Se3and Ge3Sb4Se7, were synthesized and characterized. These chalcogenides are the first ternary selenides in a ternary Ge–Sb–Se system that feature a layer structure related to black phosphorus and SnSe-type structures. Both compounds contain a ∞1[Sb2Se2]2–unit with Sb+cations in a zigzag Sb–Sb chain structure, and Sb3+cations in a distorted NaCl100-type of ∞1[Gen–2Sb2Sen]2+unit (n= 4, 5). These materials exhibit n-type semiconducting properties with thermal conductivity significantly lower than that of GeSe and Sb2Se3, which could be correlated to the 1D Sb+chain and disordered sites with different Ge/Sb compositions. It is anticipated that these newly discovered ternary chalcogenides may provide unique properties with enhanced thermoelectric properties.

Two new quaternary polyselenides, Ba4TMSbSe12(TM = Nb, Ta), are synthesized using a solid state reaction. They crystallize in a new structural type with a P‐1triclinic space group, characterized according to single‐crystal X‐ray diffraction. The structure is alternately stacked using isolated NbSe95−and SbSe33−, which are separated by Ba2+. The structure contains the NbSe95−unit with a bipentagonal pyramidal shape coordinated with Se2−and Se22−in monodenteate and bidentate modes. The vibrational property of the diselenide Se22−unit was studied using Raman spectrum analysis. ultraviolet–visible diffused reflectance and temperature‐dependent resistivity measurements indicate semiconductor behaviors. Calculations of electronic structures indicate the presence of a band gap and strong Se‐Se interactions in the diselenide group, which experimentally supports the measured physical properties. New polyselenides, Ba4TMSbSe12(TM = Nb, Ta), are synthesized and characterized. The structure is made up of TMSe95−, SbSe33−, and Ba2+.

Pyrochlore phase LixLa2−xCe1.8Ru0.2O7−δ(x= 0.0–0.6) [LLCRO] substituted by Li and Ru in A and B sites was synthesized and studied for performance in oxidative steam and auto-thermal reforming of ethanol (OSRE, ATR). The samples were characterized by powder X-ray diffraction (PXRD), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS) to examine the effect of substituted Li+and Run+on OSRE performance. The results indicated that the substituted Li ions modified the oxidation states of Ru and Ce in LLCRO, which led to oxygen vacancies/mobility and played an important role in the catalytic performance of OSRE. Using LLCRO as the catalyst and supported by Al2O3, La2Zr2O7(LZO) was investigated for its hydrogen production performance. The catalytic stability of the LLCRO (x= 0.6)/LZO catalysts was tested at 350 °C under oxidative steam conditions (OSRE) and showed a stable ethanol conversion and hydrogen production (XEtOH= 98(3)%; SH2= 95(3)%). Under autothermal conditions (ATR), the LLCRO (x= 0.6) catalyst supported by LZO exhibited a stable catalytic performance with an average ethanol conversion and hydrogen selectivity of 90(3)% and 71(4)%, respectively. Carbon deposition was significantly suppressed during the OSRE and ATR processes on LLCRO (x= 0.6) catalysts supported by LZO, whereas, a significant carbon deposition was observed for LLCRO (x= 0.6)/Al2O3as the catalyst. These results indicate that LLCRO (x= 0.6) supported by LZO is an effective catalyst for hydrogen production. The enhanced activity was attributed to the effectively suppressed carbon deposition and the sintering of highly dispersed Ru ions in the LLCRO catalyst, which may be due to the strong binding between the catalyst and LZO.