Templating fabrication of platinum nanoparticles and nanowires using the confined mesoporous channels of FSM-16—their structural characterization and catalytic performances in water gas shift reaction

Abstract The robust trigonal prismatic Pt 18 and Pt 15 cluster anions are selectively synthesized via [Pt(CO)Cl 3 ] − in FSM-16 (4.7 nm) and cis -Pt(CO) 2 Cl 2 in FSM-16 (2.8 nm) by the reductive carbonylation of H 2 PtCl 6 in the confined mesoporous channels of FSM-16, respectively. The Pt cluster anions extracted from the resulting samples in the THF solution by cation metathesis with [PPN]Cl are identified as [Pt 3 (CO) 6 ] 5 2− in FSM-16 (2.8 nm) and [Pt 3 (CO) 6 ] 6 2− in FSM-16 (4.7 nm) by the FTIR and UV–Vis spectroscopic data. The EXAFS and FTIR studies demonstrated that [Pt 3 (CO) 6 ] 5 2− /FSM-16 (2.8 nm) ( ν CO =2078, 1880 cm −1 ) and [Pt 3 (CO) 6 ] 6 2− /FSM-16 (4.7 nm) ( ν CO =2056, 1879 cm −1 ) were transformed by heating at 300–343 K into the partially decarbonylated Pt clusters (Pt–Pt; C.N.=7.6, R =2.73 A) characteristic of a linear CO band ( ν CO =2015 cm −1 ). According to the EXAFS and TEM observation, Pt carbonyl clusters are eventually converted above 473 K to naked Pt particles of 11 A (Pt–Pt C.N.=6.7, R =2.72 A) in FSM-16 (2.8 nm) and of 15 A (C.N.=7.9, R =2.74 A) in FSM-16 (4.7 nm). On the other hand, the platinum nanowires [2 and 4 nm (diameter)×50–500 nm (long)] are prepared using the cylindrical mesoporous channels of FSM-16 (2.8 and 4.7 nm) in the templating reduction of H 2 PtCl 6 by the exposure to γ-ray or UV-light ( λ max >254 nm) under the atmosphere of 2-propanol and water. It was demonstrated by the TEM observation and EXAFS characterization that the diameters of Pt nanowires formed in FSM-16 are consistent with those of FSM-16 used (2.8 and 4.7 nm), whereas the average lengths of Pt wires are varied by the function of the Pt loading mass and time exposure to γ-ray and UV-light. The observed electron beam diffraction patterns indicate that the Pt wires consist of a single crystal phase of Pt(110) having a lattice fringe of 2.27 A. It is of interest to find that the Pt nanowires in FSM-16 (2.8 nm and 4.7 nm) exhibited an unique IR spectrum in CO chemisorption and the remarkable activities per surface Pt atom (TOF) for water gas-shift reaction at 323–393 K by 60–90 times larger than those of Pt nanoparticles in FSM-16 and even conventional metal catalysts.