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At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on La2Ge4IrPd3 by Materials Project

La2IrPd3Ge4 crystallizes in the tetragonal P4mm space group. The structure is three-dimensional. there are two inequivalent La sites. In the first La site, La is bonded in a 12-coordinate geometry to eight Pd and eight Ge atoms. There are four shorter (3.37 Å) and four longer (3.39 Å) La–Pd bond lengths. There are four shorter (3.31 Å) and four longer (3.40 Å) La–Ge bond lengths. In the second La site, La is bonded in a 12-coordinate geometry to four equivalent Ir, four equivalent Pd, and eight Ge atoms. All La–Ir bond lengths are 3.38 Å. All La–Pd bond lengths are 3.37 Å. There are four shorter (3.30 Å) and four longer (3.37 Å) La–Ge bond lengths. Ir is bonded in a 5-coordinate geometry to four equivalent La and five Ge atoms. There are one shorter (2.44 Å) and four longer (2.53 Å) Ir–Ge bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent La and five Ge atoms. There are one shorter (2.47 Å) and four longer (2.56 Å) Pd–Ge bond lengths. In the second Pd site, Pd is bonded in a 4-coordinate geometry to four La and four Ge atoms. There are two shorter (2.56 Å) and two longer (2.59 Å) Pd–Ge bond lengths. There are three inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent La, one Ir, and four equivalent Pd atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent La and five Pd atoms. In the third Ge site, Ge is bonded in a 8-coordinate geometry to four La, two equivalent Ir, and two equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeIr3 by Materials Project

FeIr3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Fe is bonded to twelve equivalent Ir atoms to form FeIr12 cuboctahedra that share corners with six equivalent FeIr12 cuboctahedra, corners with twelve equivalent IrFe4Ir8 cuboctahedra, edges with eighteen equivalent IrFe4Ir8 cuboctahedra, faces with eight equivalent FeIr12 cuboctahedra, and faces with twelve equivalent IrFe4Ir8 cuboctahedra. There are six shorter (2.64 Å) and six longer (2.70 Å) Fe–Ir bond lengths. Ir is bonded to four equivalent Fe and eight equivalent Ir atoms to form distorted IrFe4Ir8 cuboctahedra that share corners with four equivalent FeIr12 cuboctahedra, corners with fourteen equivalent IrFe4Ir8 cuboctahedra, edges with six equivalent FeIr12 cuboctahedra, edges with twelve equivalent IrFe4Ir8 cuboctahedra, faces with four equivalent FeIr12 cuboctahedra, and faces with sixteen equivalent IrFe4Ir8 cuboctahedra. There are a spread of Ir–Ir bond distances ranging from 2.65–2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgIr by Materials Project

IrAg is Magnesium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ir is bonded to six equivalent Ir and six equivalent Ag atoms to form IrAg6Ir6 cuboctahedra that share corners with eighteen equivalent IrAg6Ir6 cuboctahedra, edges with six equivalent IrAg6Ir6 cuboctahedra, edges with twelve equivalent AgAg6Ir6 cuboctahedra, faces with eight equivalent IrAg6Ir6 cuboctahedra, and faces with twelve equivalent AgAg6Ir6 cuboctahedra. All Ir–Ir bond lengths are 2.76 Å. All Ir–Ag bond lengths are 2.92 Å. Ag is bonded to six equivalent Ir and six equivalent Ag atoms to form AgAg6Ir6 cuboctahedra that share corners with eighteen equivalent AgAg6Ir6 cuboctahedra, edges with six equivalent AgAg6Ir6 cuboctahedra, edges with twelve equivalent IrAg6Ir6 cuboctahedra, faces with eight equivalent AgAg6Ir6 cuboctahedra, and faces with twelve equivalent IrAg6Ir6 cuboctahedra. All Ag–Ag bond lengths are 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoIr by Materials Project

IrCo crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ir is bonded to six equivalent Ir and six equivalent Co atoms to form distorted IrCo6Ir6 cuboctahedra that share corners with eighteen equivalent IrCo6Ir6 cuboctahedra, edges with six equivalent IrCo6Ir6 cuboctahedra, edges with twelve equivalent CoCo6Ir6 cuboctahedra, faces with eight equivalent IrCo6Ir6 cuboctahedra, and faces with twelve equivalent CoCo6Ir6 cuboctahedra. All Ir–Ir bond lengths are 2.67 Å. All Ir–Co bond lengths are 2.57 Å. Co is bonded to six equivalent Ir and six equivalent Co atoms to form distorted CoCo6Ir6 cuboctahedra that share corners with eighteen equivalent CoCo6Ir6 cuboctahedra, edges with six equivalent CoCo6Ir6 cuboctahedra, edges with twelve equivalent IrCo6Ir6 cuboctahedra, faces with eight equivalent CoCo6Ir6 cuboctahedra, and faces with twelve equivalent IrCo6Ir6 cuboctahedra. All Co–Co bond lengths are 2.67 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on IrW by Materials Project

WIr crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. W is bonded to six equivalent W and six equivalent Ir atoms to form WIr6W6 cuboctahedra that share corners with eighteen equivalent WIr6W6 cuboctahedra, edges with six equivalent WIr6W6 cuboctahedra, edges with twelve equivalent IrIr6W6 cuboctahedra, faces with eight equivalent WIr6W6 cuboctahedra, and faces with twelve equivalent IrIr6W6 cuboctahedra. All W–W bond lengths are 2.81 Å. All W–Ir bond lengths are 2.77 Å. Ir is bonded to six equivalent W and six equivalent Ir atoms to form IrIr6W6 cuboctahedra that share corners with eighteen equivalent IrIr6W6 cuboctahedra, edges with six equivalent IrIr6W6 cuboctahedra, edges with twelve equivalent WIr6W6 cuboctahedra, faces with eight equivalent IrIr6W6 cuboctahedra, and faces with twelve equivalent WIr6W6 cuboctahedra. All Ir–Ir bond lengths are 2.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoSi3Ir by Materials Project

HoIrSi3 crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to four equivalent Ir and twelve Si atoms. All Ho–Ir bond lengths are 3.32 Å. There are a spread of Ho–Si bond distances ranging from 3.07–3.36 Å. Ir is bonded in a 5-coordinate geometry to four equivalent Ho and five Si atoms. There are one shorter (2.33 Å) and four longer (2.37 Å) Ir–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a distorted single-bond geometry to four equivalent Ho, one Ir, and four equivalent Si atoms. All Si–Si bond lengths are 2.56 Å. In the second Si site, Si is bonded in a distorted bent 120 degrees geometry to four equivalent Ho, two equivalent Ir, and two equivalent Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co3Ir by Materials Project

IrCo3 is beta-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ir is bonded to six equivalent Ir and six equivalent Co atoms to form IrCo6Ir6 cuboctahedra that share corners with six equivalent IrCo6Ir6 cuboctahedra, corners with twelve equivalent CoCo12 cuboctahedra, edges with six equivalent IrCo6Ir6 cuboctahedra, edges with twelve equivalent CoCo9Ir3 cuboctahedra, faces with six equivalent IrCo6Ir6 cuboctahedra, and faces with fourteen CoCo12 cuboctahedra. All Ir–Ir bond lengths are 2.62 Å. All Ir–Co bond lengths are 2.61 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded to twelve Co atoms to form CoCo12 cuboctahedra that share corners with six equivalent CoCo12 cuboctahedra, corners with twelve equivalent IrCo6Ir6 cuboctahedra, edges with eighteen CoCo12 cuboctahedra, faces with two equivalent IrCo6Ir6 cuboctahedra, and faces with eighteen CoCo12 cuboctahedra. There are six shorter (2.47 Å) and six longer (2.62 Å) Co–Co bond lengths. In the second Co site, Co is bonded to three equivalent Ir and nine Co atoms to form distorted CoCo9Ir3 cuboctahedra that share corners with eighteen equivalent CoCo9Ir3 cuboctahedra, edges with six equivalent IrCo6Ir6 cuboctahedra, edges with twelve CoCo12 cuboctahedra, faces with six equivalent IrCo6Ir6 cuboctahedra, and faces with fourteen CoCo12 cuboctahedra. All Co–Co bond lengths are 2.62 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Enhancing Acidic Oxygen Evolution Activity by Controlling Oxidation State of Iridium

Iridium oxides with high oxidation states have been reported to be effective in enhancing the acidic oxygen evolution reaction (OER) performance. Herein, we develop ultrasmall IrO x nanoparticles (NPs) over titanium nitride (TiN), which undergoes surface oxidation under oxidative conditions to form oxygen-modified TiN (oxi-TiN), enabling the formation of highly oxidized Ir δ+ (δ > 4). This IrO x /oxi-TiN catalyst delivers higher Ir mass activity than commercial IrO 2 , while comparable stability is maintained. The superior OER activity of IrO x /oxi-TiN is further demonstrated in a proton exchange membrane water electrolyzer (PEMWE), requiring only 1.88 V to reach 3 A cm −2 , achieving the U.S. Department of Energy 2025 target (1.90 V at 3 A cm −2 ). In situ X-ray absorption spectroscopy (XAS) confirms that the superior OER activity of IrO x /oxi-TiN originates from highly oxidized Ir δ+ under OER conditions. Further, density functional theory (DFT) calculations reveal a general correlation between the oxidation state of Ir and OER overpotential. Specifically, the introduction of interfacial oxygen at the Ir/TiN interface increases the oxidation state of deposited Ir δ+ from δ < 4 to δ > 4, decreasing the OER overpotential. This study highlights the critical role of high oxidation states of Ir δ+ in enhancing OER activity, providing guidance for the development of advanced acidic OER catalysts.

In situ measurements↗
DOE OSTI2025

Enhancing Acidic Oxygen Evolution Activity by Controlling Oxidation State of Iridium

Iridium oxides with high oxidation states have been reported to be effective in enhancing the acidic oxygen evolution reaction (OER) performance. In this work, we develop ultrasmall IrO x nanoparticles (NPs) over titanium nitride (TiN), which undergoes surface oxidation under oxidative conditions to form oxygen‐modified TiN (oxi‐TiN), enabling the formation of highly oxidized Ir δ+ (δ > 4). This IrO x /oxi‐TiN catalyst delivers higher Ir mass activity than commercial IrO 2 , while comparable stability is maintained. The superior OER activity of IrO x /oxi‐TiN is further demonstrated in a proton exchange membrane water electrolyzer (PEMWE), requiring only 1.88 V to reach 3 A cm −2 , achieving the U.S. Department of Energy 2025 target (1.90 V at 3 A cm −2 ). In situ X‐ray absorption spectroscopy (XAS) confirms that the superior OER activity of IrO x /oxi‐TiN originates from highly oxidized Ir δ+ under OER conditions. Density functional theory (DFT) calculations reveal a general correlation between the oxidation state of Ir and OER overpotential. Specifically, the introduction of interfacial oxygen at the Ir/TiN interface increases the oxidation state of deposited Ir δ+ from δ < 4 to δ > 4, decreasing the OER overpotential. This study highlights the critical role of high oxidation states of Ir δ+ in enhancing OER activity, providing guidance for the development of advanced acidic OER catalysts.

58 GEOSCIENCES↗
DOE OSTI2021

Noncovalent Immobilization of Pentamethylcyclopentadienyl Iridium Complexes on Ordered Mesoporous Carbon for Electrocatalytic Water Oxidation

The attachment of molecular catalysts to conductive supports for the preparation of solid-state anodes is important for the development of devices for electrocatalytic water oxidation. The preparation and characterization of three molecular cyclopentadienyl iridium(III) complexes, Cp*Ir(1-pyrenyl(2-pyridyl)ethanolate-κO,κN)Cl (1) (Cp* = pentamethylcyclopentadienyl), Cp*Ir(diphenyl(2-pyridyl)methanolate-κO,κN)Cl (2), and [Cp*Ir(4-(1-pyrenyl)-2,2'-bipyridine)Cl]Cl (3), as precursors for electrochemical water oxidation catalysts, are reported. These complexes contain aromatic groups that can be attached via noncovalent π-stacking to ordered mesoporous carbon (OMC). The resulting iridium-based OMC materials (Ir-1, Ir-2, and Ir-3) were tested for electrocatalytic water oxidation leading to turnover frequencies (TOFs) of 0.9–1.6 s -1 at an overpotential of 300 mV under acidic conditions. The stability of the materials is demonstrated by electrochemical cycling and X-ray absorption spectroscopy analysis before and after catalysis. Theoretical studies on the interactions between the molecular complexes and the OMC support provide insight onto the noncovalent binding and are in agreement with the experimental loadings.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Targeting HSPA8 inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity in imatinib-resistant chronic myeloid leukemia cells

The resistance to tyrosine kinase inhibitors is currently a major problem for chronic myeloid leukemia (CML) treatment and HSPA8 is highly expressed and a hallmark of poor prognosis in several human cancers. However, its role in imatinib-resistant CML (IR-CML) cells remains undetermined. Here, we determined HSPA8 was overexpressed in IR-CML cells and associated with imatinib resistance. HSPA8 ablation could downregulate BCR-ABL/STAT5 and BCR-ABL/AKT signaling pathways, dramatically induce proliferation inhibition, autophagy, G0/G1 phase cell cycle arrest but not apoptosis in IR-CML cells. Significantly, HSPA8 ablation enhanced the antitumor activity of imatinib via promoting apoptosis in vitro and vivo. These findings unraveled that HSPA8 ablation inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity of imatinib in IR-CML cells, which investigate the role and molecular mechanism of HSPA8 in IR-CML cells and suggest that HSPA8 may be a potential target for IR-CML treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Efficient Iridium Catalysts for Formic Acid Dehydrogenation: Investigating the Electronic Effect on the Elementary β-Hydride Elimination and Hydrogen Formation Steps

We report herein a series of Cp*Ir complexes containing a rigid 8-aminoquinolinesulfonamide moiety as highly efficient catalysts for the dehydrogenation of formic acid (FA). The complex [Cp*Ir(L)Cl] (HL = N-(quinolin-8-yl)benzenesulfonamide) displayed a high turnover frequency (TOF) of 2.97 × 10 4 h –1 and a good stability (>100 h) at 60 °C. Comparative studies of [Cp*Ir(L)Cl] with the rigid ligand and [Cp*Ir(L')Cl] (HL' = N-propylpypridine-2-sulfonamide) without the rigid aminoquinoline moiety demonstrated that the 8-aminoquinoline moiety could dramatically enhance the stability of the catalyst. The electron-donating ability of the N,N'-chelating ligand was tuned by functionalizing the phenyl group of the L ligand with OMe, Cl, and CF 3 to have a systematical perturbation of the electronic structure of [Cp*Ir(L)Cl]. Experimental kinetic studies and density functional theory (DFT) calculations on this series of Cp*Ir complexes revealed that (i) the electron-donating groups enhance the hydrogen formation step while slowing down the β-hydride elimination and (ii) the electron-withdrawing groups display the opposite effect on these reaction steps, which in turn leads to lower optimum pH for catalytic activity compared to the electron-donating groups.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

High-Resolution Photoelectron Spectroscopy of NO3 – Vibrationally Excited Along Its ν3 Mode

The nitrate (NO3) radical has long been the subject of both experimental and theoretical studies due to its complex electronic structure resulting from vibronic interactions between its X̃2A2' and B̃2E' states. In particular, the definite assignment of the fundamental of its degenerate stretching vibration (ν3) is still under debate. Here, we report high-resolution photoelectron spectra of vibrationally pre-excited NO3- using the recently developed IR-cryo-SEVI technique. The anions are excited through infrared (IR) excitation near 1350 cm-1, accessing the ν3 and 2ν3(e') vibrational levels with band centers at 1350.5 and ∼2700 cm-1, respectively. The IR-cryo-SEVI spectrum for 2ν3 pre-excitation shows clear evidence for an intense 321 transition. From the position of this feature (30031 cm-1), the electron affinity of NO3 also determined in this work (31680 cm-1), and the IR excitation energy, we obtain a fundamental frequency of 1051 cm-1 for the ν3 fundamental of the NO3 radical. This assignment and other features in the IR-cryo-SEVI spectra are supported by spectral simulations based on a vibronic Köppel-Domcke-Cederbaum Hamiltonian. The simulations also show that nearly all features in the IR-cryo-SEVI spectra arise because of pseudo-Jahn-Teller coupling between the X̃ and B̃ states of NO3. The results and analysis presented here settle a long-standing controversy regarding the ν3 frequency of NO3.

Anions↗
DOE OSTI2023

Development and Characterization of Electrodes for Surface-Specific Attenuated Total Reflection Two-Dimensional Infrared Spectroelectrochemistry

Electrochemical interfaces still have remaining mysteries surrounding the interfacial region of the electrical double layer, despite being prevalent throughout the energy and water remediation industries. The electrical double layer is where many important dynamic processes such as catalysis and electron transfer occur. The goal of this work is to study the electrical double layer with two-dimensional infrared (2D IR) spectroscopy to experimentally access the details of the structural dynamics of this complex environment. However, there are several experimental challenges to applying 2D IR spectroscopy to this application, such as assuring the surface specificity of the spectrum, optimizing the signal strength while minimizing spectral distortions from dispersion and Fano line shapes, and selecting electrode materials that are both sufficiently IR compatible and conductive. Here we will discuss various considerations when designing 2D IR experiments of electrode interfaces utilizing several substrates and experimental configurations and demonstrate a robust method for 2D IR experiments of electrode interfaces under applied potential that combines nonconducting Si ATR wafers with conductive ITO and thin nanostructured films of plasmonically active Au functionalized with 3-mercapto-2-butanone (MCB). We show that layered electrodes on thin Si ATR wafers with MCB are sensitive to applied potential and that the distortions in the linear and 2D IR spectra are heavily dependent on the morphology of the Au surface.

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

A New Cathode Material for a Li–O 2 Battery Based on Lithium Superoxide

Li–O 2 batteries suffer from large charge overpotentials due to the high charge transfer resistance of Li 2 O 2 discharge products. A potential solution to this problem is the development of LiO 2 -based batteries that possess low charge overpotentials due to the lower charge transfer resistance of LiO 2 . In this report, IrLi nanoparticles were synthesized and implemented for the first time as a LiO 2 battery cathode material. The IrLi nanoparticle synthesis was achieved by a temperature- and time-optimized thermal reaction between a precise ratio of iridium nanoparticles and lithium metal. Li–O 2 batteries employing the IrLi-rGO cathodes were cycled up to 100 cycles at moderate current densities with sustained low cell charge potentials (<3.5 V). Further, various characterization techniques, including SEM, DEMS, TEM, Raman, and titration, were used to demonstrate the LiO 2 discharge product and the absence of Li 2 O 2 . On the basis of first-principles calculations, it was concluded that the formation of crystalline LiO 2 can be stabilized by epitaxial growth on the (111) facets of IrLi nanoparticles present on the cathode surface. These findings demonstrate that, in addition to the previously studied Ir 3 Li intermetallic, the IrLi intermetallic also provides a means by which LiO 2 discharge products can be stabilized and confirms the importance of templating for the formation process.

25 ENERGY STORAGE↗
DOE OSTI2021

Single Iridium Atom Doped Ni 2 P Catalyst for Optimal Oxygen Evolution

Single-atom catalysts (SACs) with 100% active sites have excellent prospects for application in the oxygen evolution reaction (OER). However, further enhancement of the catalytic activity for OER is quite challenging, particularly for the development of stable SACs with overpotentials <180 mV. Here, we report an iridium single atom on Ni 2 P catalyst (Ir SA -Ni 2 P) with a record low overpotential of 149 mV at a current density of 10 mA·cm –2 in 1.0 M KOH. The Ir SA -Ni 2 P catalyst delivers a current density up to ∼28-fold higher than that of the widely used IrO 2 at 1.53 V vs RHE. Both the experimental results and computational simulations indicate that Ir single atoms preferentially occupy Ni sites on the top surface. The reconstructed Ir–O–P/Ni–O–P bonding environment plays a vital role for optimal adsorption and desorption of the OER intermediate species, which leads to marked enhancement of the OER activity. Additionally, the dynamic “top-down” evolution of the specific structure of the Ni@Ir particles is responsible for the robust single-atom structure and, thus, the stability property. In conclusion, this Ir SA -Ni 2 P catalyst offers novel prospects for simplifying decoration strategies and further enhancing OER performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Elucidation of Marcus Relationships for Hydride Transfer Reactions Involving Transition Metal Hydrides

The rate of hydride transfer from three Ir hydride complexes of the type Cp*Ir( R bpy)H + (Cp* = C 5 Me 5 ; R bpy = 4,4′-R-2,2′-bipyridine, R = OMe, H, CO 2 Me) to six N-methylacridinium ( R Acr + ) acceptors with electronically different substituents in the 2- or 2,7-positions were measured. Using the thermodynamic hydricity of the donors and the hydride affinity of the acceptors the thermodynamic driving forces for hydride transfer were determined. Brønsted plots, which correlate kinetic and thermodynamic hydricity, demonstrate distinct linear free energy relationships for each complex, with different Brønsted α values. Thus, at the same driving force hydride transfer from Cp*Ir( OMe bpy)H + is faster than for Cp*Ir(bpy)H + or Cp*Ir( CO2Me bpy)H + . Experimental and computational analyses are consistent with a concerted hydride transfer mechanism for all Ir complexes. As the thermodynamic driving force increases an earlier transition state is observed and all transition states also include π-stacking interactions between the donor and acceptor, which likely contribute to the different α values. The experimental data fits well to the Marcus model, enabling the determination of reorganization energies (λ) that range from 58 to 69 kcal mol -1 . These are lower than λ values for hydride transfer reactions involving organic donors and acceptors. This work provides a rare example of the correlation of kinetic and thermodynamic hydricity using only experimental data and shows that hydride transfer reactions involving metal hydrides can follow Marcus theory. Furthermore, the findings offer insight into controlling metal-catalyzed hydride transfer reactions, which is valuable for designing improved systems for a range of transformations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Heterobimetallic Iridium-Niobia Catalyst for Efficient and Selective Methane Ammonia Reforming

A Surface OrganoMetallic Chemistry (SOMC) approach, leveraging a molecularly defined heterobimetallic niobium–iridium complex, was used to prepare a mesoporous SBA-15 silica-supported Ir-NbOx catalyst. The resulting Ir-NbOx/SiO2 catalyst exhibited excellent catalytic performance in selective methane/ammonia reforming. Specifically, the Ir-NbOx/SiO2 catalyst showed significantly higher activity (turnover frequency 8.5 s–1), selectivity (75%), and stability than the Ir/SiO2 analog, whereas the NbOx/SiO2 counterpart was almost inactive. This contrasts with ethane/ammonia reforming via C–C cleavage, for which the bimetallic Ir-NbOx/SiO2 was less active than Ir/SiO2, demonstrating tuned selectivity toward C–H activation rather than C–C cleavage due to the Ir/NbOx synergy. Importantly, an Ir-NbOx/SiO2 reference catalyst, prepared by conventional impregnation/calcination/reduction steps, was found to be inactive, highlighting the value of the SOMC catalyst preparation approach using well-defined heterobimetallic precursors. These results represent a significant advance over existing catalysts due to the atomic-scale synergy between Ir and NbOx sites, enabling access to activity and selectivity regimes inaccessible to monometallic analogs.

Wu, Jiachun↗