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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Effective removal of trace-level toxic metals from flue gas desulfurization wastewater using SiO 2 supported hydrogel sorbent

Flue gas desulfurization (FGD) wastewater generated from coal-fired power plants contain potentially harmful heavy metal pollutants that pose a threat to public health and clean water. In this work, we present a water stable polyethylenimine-n,n’-methylenebisacrylamide (PEI-MBAA) functionalized SiO 2 solid sorbent material (PMS-1.2/1/4) and investigate its metal adsorption kinetics, selectivity, regenerability, and space velocity. The kinetic studies of six of the toxic heavy metals (As, Cd, Cr, Pb, Se, and Hg) prepared with single elements in Milli-Q water showed the effect of chemical bonding and intraparticle mass transfer resistance on the sorption process. The selectivity studies demonstrated the significant adsorption efficiency toward trace-level heavy metals (Se, Cd, U, Al, etc.) from authentic industrial FGD wastewater. Through five consecutive adsorption–desorption cycles with the FGD (uptake)-citrate (release)-based buffer pair, the sorbent showed high heavy metal removal ability and good reusability. The maximum flow rate for the removal of Se from industrial FGD wastewater was determined to be as high as 8 bed volumes/minute of the sorbent bed. Finally, the results demonstrate the PMS-1.2/1.4 sorbent is a promising candidate for the removal of heavy metals from practical aqueous solutions.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Reducing Non-Radiative Recombination in Perovskite Solar Cells with a SiO2-Graphene Oxide Buried Interface Layer

Perovskite solar cells (PSCs) have emerged as a transformative photovoltaic technology. However, the device performance of inverted PSCs is dramatically limited by surface defects and the underlying film morphology of metal halide perovskite (MHP) thin film. Herein, we report a novel buried interface layer consisting of SiO2 nanoparticles (NPs) chemically bonded to graphene oxide (GO), deposited atop a hydrophobic hole extraction layer (HEL) to address this limitation. The SiO2 NPs serve as insoluble scaffolds that immobilize GO sheets on the hydrophobic HEL surface, enabling the formation of homogeneous MHP thin films. Meanwhile, the GO functional groups interact with surface-uncoordinated Pb2+, suppressing interfacial defects and guiding crystal grain growth of the resultant MHP thin films. This synergistic effect suppresses non-radiative charge recombination and enhances charge extraction efficiency. As a result, a 26.07% efficiency with significantly suppressed photocurrent hysteresis is observed from PSCs incorporating the SiO2-GO buried interface layer. Moreover, the above PSCs maintain 92% of their initial PCE after 1800 h of continuous operation at the maximum power point under AM 1.5 G (100 mW/cm2) illumination at 25 degrees C in air with 50-60% relative humidity. These results demonstrate that we have developed a facile and effective way to realize high-performance inverted PSCs.

14 SOLAR ENERGY↗
DOE OSTI2022

Dramatic effect of electrode type on tunnel junction based molecular spintronic devices

A new class of molecular spintronic devices can be fabricated by chemically bonding magnetic molecular channels to the electrodes of a prefabricated tunnel junction with exposed side edges. Prior experimental studies showed that the cyanide-bridged octametallic molecular cluster, [(pzTp)FeIII(CN)3]4[NiII(L)]4¬[O3SCF3]4 [(pzTp) = tetra(pyrazol-1-yl)borate; L = 1-S(acetyl)tris(pyrazolyl)decane] molecule impact depended on the type of metallic electrodes used in the tunnel junction testbed. Experimental magnetization and transport studies showed a dramatic difference in molecule response on tunnel junctions with different combinations of metallic electrodes. Transport via paramagnetic molecular channels on a tunnel junction involving paramagnetic and ferromagnetic metal electrodes was dramatically different than the suppressed current state observed on tunnel junctions involving two ferromagnetic electrodes. We conducted theoretical studies to understand the experimental data and explore a wide range of electrode materials on tunnel junction-based molecular spintronics devices (TJMSD). Here, we report a Monte Carlo simulation study that focuses on understanding the effect of electrodes on the magnetic and physical properties of TJMSD. A 3D Heisenberg model of cross-junction-shaped TJMSD was used for the simulation study. We studied the effects of ferromagnetic, paramagnetic, and antiferromagnetic electrode materials. This study provides insights for designing and understanding futuristic molecular spintronics devices.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Aging of UV curable PDMS developed for large-scale, high viscosity stereolithography

Polydimethylsiloxane (PDMS) elastomers are silicone rubbers that find widespread application in both academic and industrial settings. This study investigates the use of photosensitive platinum catalysts for UV-activated hydrosilylation of PDMS, which enables the additive manufacturing of PDMS objects through techniques such as stereolithography. Specifically, this study focuses on understanding the aging behavior of Pt-catalyzed, UV-curable PDMS samples, including their mechanical behavior under thermal and UV-accelerated aging conditions. The results show that the Pt-catalyzed, UV-curable PDMS introduced in this research is ‘under-cured’ after being printed and will slowly evolve over time resulting in increased stiffness and decreased elongation, likely due to the formation of additional crosslinks. FTIR spectroscopy indicates that no new chemical bonds or functional groups are generated through the aging process, suggesting that no thermal degradation or polymer chain scissions occur in the polymer matrix. Overall, this PDMS formulation exhibits greater mechanical strength and significantly less reduction in strength with aging, compared with the commonly used, UV-curable thiol-ene PDMS.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Atomic Scale Crystal Field Mapping of Polar Vortices in Oxide Superlattices

Polar vortices in oxide superlattices can be utilized as potential candidates for data storage applications due to their unique polarization topologies. The structure and dipole arrangement in polar vortices has been studied via X-ray scattering techniques, (scanning) transmission electron microscopy ((S)/TEM) and computational calculations. However, the fundamental correlation between the atomic structure and the electronic structure (which is manifested in the chemical bonding) has heretofore not been explored. Further, The hybridization between nominally empty $\textit{d}$ orbitals on the B-site with the occupied O 2$\textit{p}$ orbitals favors the condensation of a polar (ferroelectric) state in $\textit{AB}$O 3 perovskite oxides. The complex, continuously rotating local polarization texture of the vortices, in turn, can result in especially intricate $\textit{d}$- orbital interactions. Soft X-ray spectroscopy can probe these interactions at the transition metal $\textit{L}$-edge, but these techniques do not have the spatial resolution to resolve variations within one vortex (~5 nm region). Electron energy loss spectroscopy (EELS) in the STEM mode uses inelastically scattered electrons to probe the core-shell excitations (empty density of states) of transition metals at atomic resolution.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Integrating computation and experiment to investigate photoelectrodes for solar water splitting at the microscopic scale.

CONSPECTUS: Photoelectrochemical water-splitting is a promising and sustainable way to store the energy of the sun in chemical bonds and use it to produce hydrogen gas, a clean fuel. The key components in photoelectrochemical cells (PECs) are photoelectrodes, including a photocathode that reduces water to hydrogen gas and a photoanode that oxidizes water to oxygen gas. Materials used in photoelectrodes for PECs must effectively absorb sunlight, yield photogenerated carriers, and exhibit electronic properties that enable the efficient shuttling of carriers to the surface to participate in relevant water-splitting reactions. Discovering and understanding the key characteristics of optimal photoelectrode materials is paramount to the realization of PEC technologies. Oxide-based photoelectrodes can satisfy many of these materials requirements, including stability in aqueous environments, band edges with reasonable alignment with the redox potentials for water splitting, and ease of synthesis. However, oxide photoelectrodes generally suffer from poor charge transport properties and considerable bulk electron-hole separation, and they have relatively large band gaps. Numerous strategies have been proposed to improve these aspects and understand how these improvements are reflected in the photoelectrochemical performance. Unfortunately, the structural and compositional complexity of multinary oxides accompanied by the inherent complexity of photoelectrochemical processes makes it challenging to understand the individual effects of composition, structure, and defects in the bulk and on the surface on a material's photoelectrochemical properties. The integration of experiment and theory has great potential to increase our atomic-level understanding of structure-composition-property relationships in oxide photoelectrodes. In this Account, we describe how integrating experiment and theory is beneficial for achieving scientific insights at the microscopic scale. We highlight studies focused on understanding the role of (i) bulk composition via solid-state solutions, intercalation, and comparison with isoelectronic compounds, (ii) dopants for both the anion and cation and their interactions with oxygen vacancies, and (iii) surface/interface structure in the photocurrent generation and photoelectrochemical performance in oxide photoelectrodes. In each instance, we outline strategies and considerations for integrating experiment and theory and describe how this integration led to valuable insights and new directions in uncovering structure-composition-property relationships. Our aim is to demonstrate the unique value of combining experiment and theory in studying photoelectrodes and to encourage the continued effort to bring experiment and theory in closer step with each other.

Wang, Wennie↗
DOE OSTI2022

Toward Ideal Metal–Organic Framework Thin-Film Growth via Automated Layer-by-Layer Deposition: Examples Based on Perylene Diimide Linkers

Photoactive metal-organic framework (MOF) thin films offer an opportunity for translating the advantages of periodic, crystalline, and tailorable light-harvesting materials directly into devices such as those for photoelectrochemical solar energy conversion. In this study, we report the fabrication of light-absorbing perylene-diimide-containing pillared-paddlewheel MOF thin films using an automated layer-by-layer (LbL) deposition technique. Our focus here is on optimizing the growth of representative chromophoric MOFs as oriented films of uniform and predefined thickness. Growth was examined as a function of metal identity, pillaring ligand composition, and supporting-surface chemical functionality. Further, application of atomic force microscopy (AFM) and complementary techniques revealed that the surface-supported MOFs initially display island-type film growth (Volmer-Weber growth), resulting in comparatively rough films. Further growth is accompanied by the merging of islands, resulting in films that, depending on experimental details, can be remarkably smooth (i.e., roughness on the order of ±1 nm (one structural repeat unit in the pillaring direction)). These details include the use of 1,4-diazabicyclo[2.2.2]octane (DABCO) as a MOF pillar and ALD-grown zinc oxide as a film support (ALD = atomic layer deposition). Also helpful for mitigating island-type growth, at least in part, is the replacement of Zn 2+ by Cu 2+ as the metal component of the MOF. Notably, each of these adjustments entails replacing weaker chemical bonds with stronger ones.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Atomically Dispersed Metals on Well-Defined Supports including Zeolites and Metal–Organic Frameworks: Structure, Bonding, Reactivity, and Catalysis

When metals in supported catalysts are atomically dispersed, they are usually cationic and bonded chemically to supports. Investigations of noble metals in this class are growing rapidly, leading to discoveries of catalysts with new properties. Characterization of these materials is challenging because the metal atoms reside on surfaces that are typically nonuniform in composition and structure. We posit that understanding of structures and catalytic properties of these materials is emerging most strongly from investigations of structurally uniform catalysts (metal atoms dispersed on crystalline supports) which can be characterized incisively with atomic-resolution electron microscopy, X-ray absorption spectroscopy, and infrared spectroscopy, bolstered by density functional theory. We assess the literature of such catalysts supported on zeotype materials, metal–organic frameworks, and covalent organic frameworks. Finally, assessing characterization, reactivity, and catalytic performance of catalysts for oxidation, hydrogenation, the water–gas shift reaction, and others, we consider metal–support interactions and ligand effects for various metal–support combinations, evaluating the degree of structural uniformity of exemplary catalysts and summarizing structure–reactivity and structure–catalytic property relationships.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Toward Realistic Models of the Electrocatalytic Oxygen Evolution Reaction

The electrocatalytic oxygen evolution reaction (OER) supplies the protons and electrons needed to transform renewable electricity into chemicals and fuels. However, the OER is kinetically sluggish; it operates at significant rates only when the applied potential far exceeds the reversible voltage. The origin of this overpotential is hidden in a complex mechanism involving multiple electron transfers and chemical bond making/breaking steps. Our desire to improve catalytic performance has then made mechanistic studies of the OER an area of major scientific inquiry, though the complexity of the reaction has made understanding difficult. While historically, mechanistic studies have relied solely on experiment and phenomenological models, over the past twenty years ab initio simulation has been playing an increasingly important role in developing our understanding of the electrocatalytic OER and its reaction mechanisms. In this Review we cover advances in our mechanistic understanding of the OER, organized by increasing complexity in the way through which the OER is modeled. We begin with phenomenological models built using experimental data before reviewing early efforts to incorporate ab initio methods into mechanistic studies. We go on to cover how the assumptions in these early ab initio simulations-no electric field, electrolyte, or explicit kinetics-have been relaxed. Through comparison with experimental literature, we explore the veracity of these different assumptions. We summarize by discussing the most critical open challenges in developing models to understand the mechanisms of the OER.

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

Metal–Organic Frameworks as Catalysts for (De)Hydrogenation: Progress, Challenges, and Perspectives

Storing hydrogen through chemical bonding in liquid-organic hydrogen carriers (LOHCs) offers a safer and more practical approach for hydrogen transportation compared to physical liquefaction, which is limited by low volumetric efficiency and gas release. The efficiency of LOHC systems is highly dependent on effective catalysts, which are typically composed of transition metals supported on metal oxides. However, these materials often rely upon costly noble metals, and their nonuniform nature limits mechanistic insights and structure–function relationships that could improve catalyst design. Metal–organic frameworks (MOFs) are promising alternatives to existing catalysts due to their crystalline, tunable, and porous nature. However, their use as catalysts for (de)hydrogenation reactions remains largely underexplored. Related to this, we identify two general classes of MOFs reported as catalysts for (de)hydrogenation reactions: MOFs as scaffolds for catalytically active species and MOFs that function as reactive materials themselves. MOF composites anchor reactive nanoparticles or homogeneous species, imparting reactivity to the framework. The confinement effects experienced by the affixed species, combined with favorable substrate adsorption interactions or acid sites provided by the MOF, enhance the stability, selectivity, and activity of these catalysts for (de)hydrogenation reactions. Additionally, catalytically active MOFs often feature open metal sites at the node or undergo postsynthetic modification at either node or linker to impart reactivity. Here, taking inspiration from these materials, we outline the current state and key challenges of utilizing MOFs as (de)hydrogenation catalysts and propose research pathways to advance materials in this field for energy applications.

Catalysts↗
DOE OSTI2024

Density Functional Tight-Binding Models for Band Structures of Transition-Metal Alloys and Surfaces across the d -Block

First-principles electronic structure simulations are an invaluable tool for understanding chemical bonding and reactions. While machine-learning models such as interatomic potentials significantly accelerate the exploration of potential energy surfaces, electronic structure information is generally lost. Particularly in the field of heterogeneous catalysis, simulated electron band structures provide fundamental insights into catalytic reactivity. This ab initio knowledge is preserved in semiempirical methods such as density functional tight binding (DFTB), which extend the accessible computational length and time scales beyond first-principles approaches. In this paper here we present Shell-Optimized Atomic Confinement (SOAC) DFTB electronic-part-only parametrizations for bulk and surface band structures of all d-block transition metals that enable efficient predictions of electronic descriptors for large structures or high-throughput studies on complex systems outside the computational reach of density functional theory.

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

Diabatic Valence-Hole States in the C 2 Molecule: “Putting Humpty Dumpty Together Again”

Despite the long history of spectroscopic studies of the C$_2$ molecule, fundamental questions about its chemical bonding are still being hotly debated. The complex electronic structure of C$_2$ is a consequence of its dense manifold of near-degenerate, low-lying electronic states. A global multi-state diabatic model is proposed here to disentangle the numerous configuration interactions within four symmetry manifolds of C$_2$ ($^{1}\Pi_g$, $^{3}\Pi_g$, $^{1}\Sigma_u^+$, and $^{3}\Sigma_u^+$). The key concept of our model is the existence of two "valence-hole" configurations, $2\sigma_g^22\sigma_u^11\pi_{u}^33\sigma_g^2$ for $^{1,3}\Pi_g$ states and $2\sigma_g^22\sigma_u^11\pi_{u}^43\sigma_g^1$ for $^{1,3}\Sigma_u^+$ states that derive from $3\sigma_g\leftarrow2\sigma_u$ electron promotion. The lowest-energy state from each of the four C$_2$ symmetry species is dominated by this type of valence-hole configuration at its equilibrium internuclear separation. Finally, as a result of their large binding energy (nominal bond order of 3) and correlation with the 2s$^2$2p$^2$+2s2p$^3$ separated-atom configurations, the presence of these valence-hole configurations has a profound impact on the $global$ electronic structure and unimolecular dynamics of C$_2$.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Oxygen K-Edge X-ray Absorption Spectra of ThO 2 and CeO 2 : Experiment, Interpretation, and Structural Effects

Experimental oxygen K-edge spectra of ThO 2 and CeO 2 are presented and interpreted based on density functional theory (DFT). The contribution of d and f orbitals to the O K-edge spectrum is identified as well-distinguished peaks, the presence of which evidences the strong hybridization of Th and Ce metal centers with O orbitals. The sensitivity of the O K-edge to both f- and d-states in the absence of a core–hole on the metal ion results in an insightful overview of the electronic structure involved in the chemical bond. In particular, the large bandwidth of the Th 5f band as compared to the Ce 4f band is observed as a set of wider and more substantial set of peaks in the O K-edge, confirming the stronger hybridization of the former with O orbitals. The peak ascribed to the 5f band of ThO 2 is found at higher energy than the 6d band, as predicted from DFT calculations on actinide dioxides. Here, to highlight the sensitivity and the potential use of the O K-edge for the characterization of ThO 2 -based systems, the sensitivity of the spectrum to structural changes such as lattice expansion and size reduction are calculated and discussed.

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

Interfacial Properties of Gold and Cobalt Oxyhydroxide in Plasmon-Mediated Oxygen Evolution Reaction

Water electrolysis is one green approach of storing electrical energy within chemical bonds of the high-energy hydrogen gas (H2). The anodic reaction involved in the oxygen evolution reaction (OER) requires high kinetic overpotential on the overall rate of the process. Recently, plasmonic gold nanoparticles (Au NPs) have been added to enhance the charge transfer at the interface of the OER electrocatalysts and electrolyte under light illumination. However, mechanistic understanding of how Au NPs on the photo-assisted electrochemical process is still lacking. We applied a model system of plasmonic Au electrode and a cobalt (Co)-based OER electrocatalyst in alkaline electrolytes to investigate the plasmon-mediated OER process with (photo)electrochemical and spectroscopic studies. Our results demonstrated that the electrodeposited and surfactant-free plasmonic Au electrode could enhance the electrocatalytic performances of the Co-based electrocatalysts in the OER process with continuous visible and near infrared light illumination. Both the photothermal and energetic charge carriers were found to contribute to the enhanced OER performance based on the transient photocurrent studies, and the interfaces of Au and the Co-based electrocatalysts determined the enhancement mechanisms. The active phase of the cobalt based OER electrocatalyst at operating potentials was identified with electrochemical Raman measurements.

OER↗
DOE OSTI2025

Stabilization of Preternatural Barium Oxidation States as an Unexpected Byproduct of β-Decay: Discovery of a New Halide Semiconductor Alloy

137 Cs has a wide range of roles in the nuclear industry. The solid material, safely encapsulated in CsCl as 137 CsCl, is stored as fission product waste from nuclear power production and legacy waste from nuclear weapons production; it has also served as a radiation source in food and sewage irradiators as well as medical devices. However, because of the solubility of the chloride salt and the relatively high specific activity of 137 Cs, damaged or broken capsules can lead to severe radiological accidents. Safe capsule design and material recycling are complicated by the unclear structural evolution during β-decay, which remains ambiguous due to the differing oxidation states of Cs (1+) and Ba (2+). Here, in this study, we use first-principles calculations to investigate the evolving structure–property relationships of Cs 1–x Ba x Cl during β-decay. Despite the well-established 2+ formal oxidation state of alkali-earth metals, we find that Ba 1+ can be stabilized in the form of a mixed-valence alloy at low concentrations. Specifically, we identify three regimes for the β-decay of 137 Cs into CsCl: Ba-doped CsCl (Ba ≤ 14%), wherein Ba has the expected 2+ oxidation state; Cs–Ba–Cl alloys, where Ba has a mix of the usual Ba 2+ and highly unusual Ba 1+ oxidation state in the form of a quasi-disordered mixed-valence alloy (Ba = 25%); and phase separation into a CsCl + BaCl 2 + Ba (m) mechanical mixture, where Ba reverts to its expected 2+ oxidation state (Ba > 25%). Surprisingly, the Cs 0.75 Ba 0.25 Cl mixed-valence alloy is a narrow indirect band gap semiconductor (1.05 eV) despite the insulating nature of both CsCl and BaCl 2 . It also exhibits strongly excitonic polarized optical properties, has glass-like ultralow thermal conductivity (directional average of 0.21 W/mK at 300 K), and shows greater resistance to deformation under both tensile and volumetric strengths compared with the original CsCl structure (e.g., shear and Young’s modulus of 9.04 and 31.62 GPa, respectively). These findings imply that transmutation of 137 Cs leads to highly unusual chemical bonding that stabilizes Ba 1+ in local regions of the quasi-disordered Cs 0.25 Ba 0.75 Cl, resulting in anomalous physical properties. Moreover, this discovery provides valuable insight for safe nuclear waste capsule design, which can aid in preventing environmental or human exposure to radioactive materials.

Fuhr, Addis S. [Oak Ridge National Laboratory (ORN↗
DOE OSTI2021

Preparation of Ultrathin Gold Films with Subatomic Surface Roughness

Nanoscale device fabrication requires control over film growth at the atomic scale. Growth conditions must be tuned in consideration of interface parameters like chemical bonding, surface free energy, and lattice matching. In metals, electronic properties may also be utilized for control of physical parameters. Quantum size effects can induce metals to spontaneously form specific shapes and sizes according to their electronic structure. Unfortunately, such electronic growth is generally known only for a few systems and is typically only stable under cryogenic conditions. In this work, we explore a recently discovered class of electronic growth systems in which metal films are grown upon the relatively inert surfaces of van der Waals crystals. In this class of materials, the electronic growth is highly stable at room temperature and actually requires higher temperature annealing to achieve proper equilibrium. We work with the Au/MoS 2 system, which shows excellent stability and can readily form discrete and atomically flat nanostructures. Here, we show how the electronic growth modes facilitate the formation of atomically flat films with nanometer scale thickness. Here, the surface roughness of these films was found to be less than a single atom over several square microns, creating nearly perfect surfaces for studies of self-assembled monolayers or other applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Estimating Internal Stress of an Alteration Layer Formed on Corroded Boroaluminosilicate Glass through Spectroscopic Ellipsometry Analysis

Aqueous corrosion of glass may result in the formation of an alteration layer in the glass surface of which chemical composition and network structure are different from those of the bulk glass. Since corrosion occurs far below the glass-transition temperature, the alteration layer cannot fully relax to the new structure with the lowest possible energy. Molecular dynamics simulations suggested that such a network will contain highly strained chemical bonds, which can be manifested as a stress in the alteration layer. Common techniques to measure stress in thin films or surface layers were found inadequate for thick monolithic glass samples corroded in water. Here, we explored the use of spectroscopic ellipsometry to test the presence of internal stress in the alteration layer formed by aqueous corrosion of glass. Furthermore, a procedure for analyses of spectroscopic ellipsometry data to determine birefringence in the alteration layer was developed. Findings with the established fitting procedure suggested that a stress builds up in the corroded surface layer of a boroaluminosilicate glass if there is a change in relative humidity, pH, or electrolyte concentration of the environment to which the glass surface is exposed. A similar process may occur in other types of glass, and it may affect the surface properties of corroded glass objects.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Selective and Stable In-Promoted Fe Catalyst for Syngas Conversion to Light Olefins

A selective and stable alumina-supported In-promoted Fe catalyst (10 mol % In based on Fe) was discovered for converting syngas (2:1 H 2 /CO ratio) to olefins with high selectivity (45% with CO 2 included) and a remarkable stability (72 h run) at a CO conversion of 10% at 400 °C and 5 bar. The X-ray photoelectron spectroscopy results indicated that incorporating In into Fe catalysts changed the chemical bonding state of Fe and Fe/In composition near the surface layers, which affected the catalytic reactivity. Steady-state isotopic transient kinetic analysis showed that more stable CHx fragments are present on the catalyst surface when incorporating In into Fe, which can promote C–C coupling reaction toward olefins. Our study demonstrates that introducing In into Fe catalysts on Al 2 O 3 support can lower CO activation abilities. It has more impacts on lowering hydrogenation activity, which permits more C–C couplings and like of “ene” hydrogenation. Furthermore, weakening CO adsorption both in terms of sites and strength encouraged CO toward hydrocarbons rather than CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗