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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on IrPd by Materials Project

PdIr is Copper-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are three inequivalent Ir sites. In the first Ir site, Ir is bonded to six equivalent Ir and six equivalent Pd atoms to form IrIr6Pd6 cuboctahedra that share corners with twelve IrIr6Pd6 cuboctahedra, edges with twelve IrIr6Pd6 cuboctahedra, edges with twelve equivalent PdIr6Pd6 cuboctahedra, faces with six equivalent IrIr6Pd6 cuboctahedra, and faces with twelve equivalent PdIr6Pd6 cuboctahedra. All Ir–Ir bond lengths are 2.76 Å. All Ir–Pd bond lengths are 2.76 Å. In the second Ir site, Ir is bonded to six equivalent Ir and six Pd atoms to form IrIr6Pd6 cuboctahedra that share corners with five equivalent PdIr6Pd10 cuboctahedra, corners with twelve IrIr6Pd6 cuboctahedra, edges with ten PdIr6Pd6 cuboctahedra, edges with twelve IrIr6Pd6 cuboctahedra, faces with six equivalent IrIr6Pd6 cuboctahedra, and faces with fifteen PdIr6Pd6 cuboctahedra. All Ir–Ir bond lengths are 2.76 Å. All Ir–Pd bond lengths are 2.76 Å. In the third Ir site, Ir is bonded to six equivalent Ir and six Pd atoms to form IrIr6Pd6 cuboctahedra that share corners with five equivalent PdIr6Pd10 cuboctahedra, corners with twelve IrIr6Pd6 cuboctahedra, edges with ten PdIr6Pd6 cuboctahedra, edges with twelve IrIr6Pd6 cuboctahedra, faces with six equivalent IrIr6Pd6 cuboctahedra, and faces with fifteen PdIr6Pd6 cuboctahedra. All Ir–Ir bond lengths are 2.76 Å. All Ir–Pd bond lengths are 2.76 Å. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded to six Ir and six equivalent Pd atoms to form PdIr6Pd6 cuboctahedra that share corners with twelve PdIr6Pd6 cuboctahedra, edges with twelve IrIr6Pd6 cuboctahedra, edges with twelve PdIr6Pd6 cuboctahedra, faces with six equivalent PdIr6Pd6 cuboctahedra, and faces with twelve IrIr6Pd6 cuboctahedra. All Pd–Pd bond lengths are 2.76 Å. In the second Pd site, Pd is bonded to six Ir and ten equivalent Pd atoms to form PdIr6Pd10 cuboctahedra that share corners with ten IrIr6Pd6 cuboctahedra, corners with twelve PdIr6Pd6 cuboctahedra, edges with eight IrIr6Pd6 cuboctahedra, edges with sixteen PdIr6Pd6 cuboctahedra, faces with sixteen equivalent PdIr6Pd10 cuboctahedra, and faces with eighteen IrIr6Pd6 cuboctahedra. There are a spread of Pd–Pd bond distances ranging from 2.76–5.52 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Single-step selective oxidation of methane to methanol in the aqueous phase on iridium-based catalysts

In this work, one-step conversion of methane to methanol using molecular oxygen as the oxidant in the presence of CO in aqueous solutions on copper or palladium promoted Ir-ZSM-5 catalyst is first reported. The addition of a second metal to Ir-ZSM-5 promotes the catalyst activity, while product selectivity can be tuned either to methanol on IrCu-ZSM-5 or to formic acid exclusively on IrPd-ZSM-5. Most effective is the combination of the three metal species together. Approximately 1200 μmol/g cat methanol, or ~23.4 mol of methanol per mol of Ir, are formed on the IrCuPd trimetallic system (methanol selectivity ~80 %) at 150 °C in 1 h. Our results also demonstrate that atomically dispersed Ir(I)(CO) 2 species formed in the presence of CO can activate the C–H bond of methane to methyl species at temperatures below 150 °C. The good stability in cyclic operation is an additional attribute, rendering this type of catalyst a “front-runner” in future catalyst development for direct methane-to-liquid oxygenates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Binding of saturated and unsaturated C 6 -hydrocarbons to the electrophilic anion [B 12 Br 11 ] – : a systematic mechanistic study

The highly reactive gaseous ion [B 12 Br 11 ] – is a metal-free closed-shell anion which spontaneously forms covalent bonds with hydrocarbon molecules, including alkanes. Herein, we systematically investigate the reaction mechanism for binding of [B 12 Br 11 ] – to the five hexane isomers yielding [B 12 Br 11 (C 6 H 14 )] – , as well as to cyclohexane and several hexene isomers (yielding [B 12 Br 11 (C 6 H 12 )] – ) using collision-induced dissociation (CID), infrared photodissociation spectroscopy (IRPD) and computational methods. CID of the different [B 12 Br 11 (C 6 H 14 )] – ions results in distinct fragmentation patterns dependent on the structure of the hexane isomer. Further, the observed fragmentation reactions provide insights into the addition mechanism of [B 12 Br 11 ] – to hexane. Based on the observed CID patterns, we identified that either B–C bond formation through heterolytic C–C or C–H bond cleavages or B–H bond formation through heterolytic C–H cleavage occur dependent on the structure of the hexane isomer. Meanwhile, we observe identical CID spectra of adducts originating from isomers of C 6 H 12 . Spectroscopic investigations of adducts of 1-hexene and cyclohexane indicate the same product structure with an open C 6 chain. Computational investigations evidenced that low lying transition states are present, which enable a ring opening reaction of cyclohexane when binding to [B 12 Br 11 ] – .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗