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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Synthetic Access to a Framework-Stabilized and Fully Sulfided Analogue of an Anderson Polyoxometalate that is Catalytically Competent for Reduction Reactions

Polyoxometalates (POMs) featuring 7, 12, 18, or more redox-accessible transition metal ions are ubiquitous as selective catalysts, especially for oxidation reactions. The corresponding synthetic and catalytic chemistry of stable, discrete, capping-ligand-free polythiometalates (PTMs), which could be especially attractive for reduction reactions, is much less well developed. Among the challenges are the propensity of PTMs to agglomerate and the tendency for agglomeration to block reactant access of catalyst active sites. Nevertheless, the pervasive presence of transition metal sulfur clusters metalloenzymes or cofactors that catalyze reduction reactions and the justifiable proliferation of studies of two-dimensional (2D) metal-chalcogenides as reduction catalysts point to the promise of well-defined and controllable PTMs as reduction catalysts. Here, we report the fabrication of agglomeration-immune, reactant-accessible, capping-ligand-free Co II Mo 6 IV S 24 n– clusters as periodic arrays in a water-stable, hierarchically porous Zr-metal–organic framework (MOF; NU1K) by first installing a disk-like Anderson polyoxometalate, Co III Mo 6 VI O 24 m– , in size-matched micropores where the siting is established via difference electron density (DED) X-ray diffraction (XRD) experiments. Flowing H 2 S, while heating, reduces molybdenum(VI) ions to Mo(IV) and quantitatively replaces oxygen anions with sulfur anions (S 2– , HS – , S 2 2– ). DED maps show that MOF-templated POM-to-PTM conversion leaves clusters individually isolated in open-channel-connected micropores. Importantly, the structure of the immobilized cluster as determined, in part, by X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) analysis, and pair distribution function (PDF) analysis of total X-ray scattering agrees well with the theoretically simulated structure. PTM@MOF displays both electrocatalytic and photocatalytic competency for hydrogen evolution. Nevertheless, the initially installed PTM appears to be a precatalyst, gaining competency only after the loss of ~3 to 6 sulfurs and exposure to hydride-forming metal ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

MSU-Northern Bio-Energy Center of Excellence

The goal of this project was to establish the Bio-Energy Center (the Center) of Montana State University Northern (MSUN) as a Regional Research Center of Excellence in research, product development, and commercialization of non-food biomass for the bio-energy industry. A three-step approach, namely, (1) enhance the Center’s research and testing capabilities, (2) develop advanced biofuels from locally grown agricultural crops, and (3) educate the community through outreach programs for public understanding and acceptance of new technologies was identified to achieve this goal. The research activities aimed to address the obstacles concerning the production of biofuels and other bio-based fuel additives considering feedstock quality, conversion process, economic viability, and public awareness. First and foremost in enhancing the capabilities of the Center is the improvement of its laboratories and other physical facilities for investigating new biomass conversion technologies and the development of its manpower complement with expertise in chemistry, engineering, biology, and energy. MSUN renovated its Auto Diagnostics building and updated its mechanical and electrical systems necessary to house the state-of-the-art 525kW (704 hp) A/C Dynamometer. The newly renovated building was designated as the Advanced Fuels Building. Two laboratories, namely Biomass Conversion lab and Wet Chemistry lab were also added to the Center’s facilities. The Biomass Conversion lab was for research on the production of advanced biofuels including bio-jet fuel and bio-based fuel additives while the Wet Chemistry lab was used to conduct catalyst research. Necessary equipment and machines, such as gas chromatograph-mass spectrometry, were purchased and installed to help in research and testing. With the enhanced capabilities of the Center, research and testing activities were very much facilitated and more precise. New biofuels derived from Camelina sativa (camelina), a locally-grown oilseed crop was developed through a chemical process for converting the oil extracted into jet fuel. Promising methods of synthesizing heterogeneous metal complex catalyst that support the chemical conversion process were likewise developed. Breaking-down lignin to valuable chemicals using a metal complex catalyst was also investigated. Lignin is an organic polymer that binds around cellulose and hemicellulose fibers which strengthen cell walls in woody biomass. Test results showed promise and could lead to further exploration of using lignin for fuels and fuel additives. These findings could create another value-added product from lignin that can be sourced from beetle kill trees and product residues from cellulose ethanol plants. Coupled with these research discoveries was the provision of technical support to businesses in terms of product development and commercialization of bio-based products. This in turn opened new avenues for advancing the bio-energy industry in the region and helped support the regional agricultural-based economy through developing biofuels derived from feedstock that are grown locally. It assisted in developing biofuels that reduce exhaust emissions and improve engine performance.

09 BIOMASS FUELS↗
DOE OSTI2021

Oxygen Vacancies Enriched Bi Based Catalysts for Enhancing Electrocatalytic CO2 Reduction to Formate

The practical application of CO2 conversion through electrochemical reduction is still hindered by the lack of high performance and cost-effective catalysts. It is thus imperative to explore feasible strategies for scalable fabrication of catalysts for CO2 reduction to targeting products with high efficiency. Herein, for the first time, a hybrid of BiOx encapsulated in carbon thin layer is developed as high active electrocatalyst for CO2 conversion, which is synthesized by pyrolysis using Bi MOF as precursor and sacrificial template. The carbon layer overcoating BiOx catalyst exhibits superior performance for CO2 reduction to formate, achieving a maximum Faradaic efficiency of 89.3 % and a maximum current density of 37.8 mA cm-2. It is found that the as-prepared BiOx catalyst is enriched with oxygen vacancies stabilized by the encapsulating carbon layer. Both the carbon layer and oxygen vacancies improve the charge transfer of the catalyst, in favor of the high formate current density. The defects of oxygen vacancies play a vital role in CO2 adsorption and activation and thereby further enhancing the electrocatalytic ability for formate production.

oxygen vacancy, bismuth, carbon coating, CO2 elect↗
DOE OSTI2021

Designing a Zn–Ag Catalyst Matrix and Electrolyzer System for CO 2 Conversion to CO and Beyond

CO 2 emissions can be transformed into high-added-value commodities through CO 2 electrocatalysis; however, efficient low-cost electrocatalysts are needed for global scale-up. Inspired by other emerging technologies, the authors report the development of a gas diffusion electrode containing highly dispersed Ag sites in a low-cost Zn matrix. Here, this catalyst shows unprecedented Ag mass activity for CO production: –614 mA cm –2 at 0.17 mg of Ag. Subsequent electrolyte engineering demonstrates that halide anions can further improve stability and activity of the Zn–Ag catalyst, outperforming pure Ag and Au. Membrane electrode assemblies are constructed and coupled to a microbial process that converts the CO to acetate and ethanol. Combined, these concepts present pathways to design catalysts and systems for CO 2 conversion toward sought-after products.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Liquefaction of Forest Biomass to "Drop-in" Hydrocarbon Biofuels

The overall goal of the project was to demonstrate solvent liquefaction as a viable path to stable intermediates for subsequent upgrading to fuel blendstocks. Iowa State University (ISU) utilized technology developed by Chevron to produce “green crude” via continuous biomass liquefaction to bio-oil without catalyst or reducing gas, then upgraded the crude to drop-in hydrocarbon liquid transportation fuels. Original benchmarks for the project included conversion of biomass to bio-oil at a yield of 50% or more, produce bio-oil with oxygen content below 20 wt%, and recycle a portion of the bio-oil product for use as solvent, displacing initial hydrocarbon solvent. Initial testing and technology development was completed by Chevron using a custom Small Continuous Liquefaction Unit (SCLU) operated in “once-through” mode. In this system, liquid product and solid residual/char was collected together and required both off-line solids removal and product separation. This unit was disassembled and major components incorporated into a redesigned solvent liquefaction system at ISU capable of processing biomass at rates up to 1 kg/h. Online, continuous solids separation and bio-oil recovery/separation systems were successfully implemented. Online solids removal using an acetone injection to aid in separation achieved over 99% solids removal efficiency, and acetone recovery of greater than 97% was achieved. The gas stripping system developed for the separation of medium wood oil (MWO) for the recycle stream from the heavy wood oil (HWO) product stream was also successful in recovering approximately 93 wt% of the initial solvent from the biomass-derived products. Due to the generation of fine particulate and the high molecular weight of the HWO which both negatively affect the ability to separate the product oil, solvent recycle was not fully implemented in the system. The biomass used in this project is loblolly pine forest residue. The solvent was a blend of two hydrocarbon liquids. The majority of the solvent was comprised of commercially available naphthalene-depleted heavy aromatic solvent. The hydrogen donor solvent was a proprietary cut of light cycle oil (LCO) that was hydrotreated. As much as 25 wt% of the solvent mixture was comprised of the hydrotreated LCO. Higher blend ratios were limited by the economics of providing hydrogen to the process in this manner. Two cases were evaluated for technical feasibility on the SCLU. These are 1. Simulated phenolic solvent recycle and 2. Hydrocarbon-rich solvent processing. The simulated phenolic solvent recycle case was based on an idealistic solvent mixture where only 5% makeup or hydrogen donor solvent entered the system. The resulting solvent mixture at steady state was estimated to be 75 wt% depleted hydrogen donor, 20 wt% biomass derived phenolic monomers, and 5 wt% HLCO. This case resulted in the highest bio-oil organic yield observed in the project of 66.7 wt% on a solvent-less, dry biomass basis and relatively low oxygen content of 12%. Additionally, these conditions deconstructed the biomass so well, that extremely fine particulate was generated such that 5 micron barrier filters were unable to remove the material. Offline addition of acetone, centrifugation and acetone removal were required in order to remove the particulate prior to fractionation with the stripping column. The resulting HWO had a high molecular weight and was therefore very viscous in nature, remaining solid at room temperature. Additionally, the column was unable to sustainably strip enough MWO to close the recycle loop balance while maintaining flowability of product oil exiting the column. It was determined that additional HLCO would be required at the front of the process to decrease product viscosity both by dilution and additional hydrogen transfer into the HWO product oil. The hydrocarbon rich mixture was the preferred mixture for a majority of the project and featured a 25% donor or HLCO content and 75% depleted hydrogen donor mix. A series of three tests were conducted using this mixture and serve as the basis for a paper detailing the system. While the online acetone injection system for high pressure solids removal was demonstrated early on using this mixture, difficulty controlling process flows led to the use of an atmospheric stirred tank filtration system. At these high donor solvent levels, the product stream easily partitioned with sufficient MWO to close the recycle loop balance. Additionally, this mixture produced HWO product oil at just over 55% yield, <5% oxygen content, and a reasonable viscosity at room temperature. A 56 hour campaign was conducted with the ISU pilot to produce a large enough batch of HWO product oil to conduct upgrading experiments at Chevron’s Richmond, CA facility. Benchtop hydrotreating units were used to conduct long-duration hydrogenation/hydrogenolysis reactions in order to provide yield data and help validate assumptions made in the TEA model. Resulting products featured an oxygen content of <1%, near the detectability limit. Hydrocracking simulations were also performed, and a distribution of heavy wood oil to refinery products was determined. These distributions are based on a database of commercial and pilot plant operation used by Chevron to estimate product yield from novel inputs based on the input physical and chemical characteristics. While multi-week benchtop hydrotreating tests were successfully conducted without fouling, analysis and testing of the heavy wood oil suggest it may be better suited for hydrocracking. Metals content in the heavy wood oil would likely create catalyst fouling over time and reduce lifetime of hydrotreating catalysts. Yields and product partitioning were also more favorable from hydrocracking compared to those from hydrotreating.

09 BIOMASS FUELS↗
DOE OSTI2020

Gel‐Derived Amorphous Bismuth–Nickel Alloy Promotes Electrocatalytic Nitrogen Fixation via Optimizing Nitrogen Adsorption and Activation

Abstract To achieve the electrochemical nitrogen reduction reaction (NRR) for efficient and sustainable NH 3 production, catalysts should exhibit high selectivity and activity with optimal adsorption energy. Herein we developed a three‐dimensional (3D) amorphous BiNi alloy toward a significantly enhanced NRR compared with its crystalline and metal counterparts. Ni alloying enables the chemisorption of nitrogen and the lower free‐energy change for the *NNH formation, and the 3D alloy electrocatalyst exhibits high catalytic activity for NH 3 production with a yield rate of 17.5 μg h −1 mg cat −1 and Faradaic efficiency of 13.8 %. The enhanced electron transfer and increased electrochemical surface area were revealed in the interconnected porous scaffold, affording it sufficiently efficient and stable activity for potential practical applications. This work offers new insights into optimizing the adsorption energy of reactants and intermediates combined with tuning the crystallinity of NRR electrocatalysts.

Fang, Zhiwei↗
DOE OSTI2021

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN 4 Active Sites

Abstract We elucidate the structural evolution of CoN 4 sites during thermal activation by developing a zeolitic imidazolate framework (ZIF)‐8‐derived carbon host as an ideal model for Co 2+ ion adsorption. Subsequent in situ X‐ray absorption spectroscopy analysis can dynamically track the conversion from inactive Co−OH and Co−O species into active CoN 4 sites. The critical transition occurs at 700 °C and becomes optimal at 900 °C, generating the highest intrinsic activity and four‐electron selectivity for the oxygen reduction reaction (ORR). DFT calculations elucidate that the ORR is kinetically favored by the thermal‐induced compressive strain of Co−N bonds in CoN 4 active sites formed at 900 °C. Further, we developed a two‐step (i.e., Co ion doping and adsorption) Co‐N‐C catalyst with increased CoN 4 site density and optimized porosity for mass transport, and demonstrated its outstanding fuel cell performance and durability.

He, Yanghua↗
DOE OSTI2020

Gel-Derived Amorphous Bismuth–Nickel Alloy Promotes Electrocatalytic Nitrogen Fixation via Optimizing Nitrogen Adsorption and Activation

To achieve the electrochemical nitrogen reduction reaction (NRR) for efficient and sustainable NH 3 production, catalysts should exhibit high selectivity and activity with optimal adsorption energy. Herein we developed a three-dimensional (3D) amorphous BiNi alloy toward a significantly enhanced NRR compared with its crystalline and metal counterparts. Ni alloying enables the chemisorption of nitrogen and the lower fre-energy change for the *NNH formation, and the 3D alloy electrocatalyst exhibits high catalytic activity for NH 3 production with a yield rate of 17.5 μg h -1 mg cat -1 and Faradaic efficiency of 13.8 %. The enhanced electron transfer and increased electrochemical surface area were revealed in the interconnected porous scaffold, affording it sufficiently efficient and stable activity for potential practical applications. Furthermore, this work offers new insights into optimizing the adsorption energy of reactants and intermediates combined with tuning the crystallinity of NRR electrocatalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Selective Oxidation of Lignin Model Compounds

Lignin, the planet's most abundant renewable source of aromatic compounds, is difficult to degrade efficiently to welldefined aromatics. We developed a microwave-assisted catalytic Swern oxidation system using an easily prepared catalyst, MoO 2 Cl 2 (DMSO) 2 , and DMSO as the solvent and oxidant. It demonstrated high efficiency in transforming lignin model compounds containing the units and functional groups found in native lignins. The aromatic ring substituents strongly influenced the selectivity of β-ether phenolic dimer cleavage to generate sinapaldehyde and coniferaldehyde, monomers not usually produced by oxidative methods. Time-course studies on two key intermediates provided insight into the reaction pathway. Finally, owing to the broad scope of this oxidation system and the insight gleaned with regard to its mechanism, this strategy could be adapted and applied in a general sense to the production of useful aromatic chemicals from phenolics and lignin.

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

Preface to Special Issue on Neutron Scattering for Catalysis

In the pursuit of understanding the chemical transformations of catalytic reactions and the structural evolution of catalysts at the molecular level, a suite of advanced experimental methods has been developed in the studies of catalysis science. Furthermore, among these methods, neutron scattering not only gives catalytic information that is highly complementary to other microscopic scattering techniques such as electrons (microscopy and diffraction) and photons from visible light to synchrotron X-rays, but also frequently provides unique insights into catalysis regarding the structure and chemical nature of light elements such as hydrogen and oxygen that are either not possible or difficult to study with other approaches.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

High-performance oxygen reduction and evolution carbon catalysis: From mechanistic studies to device integration

The development of high-performance and low-cost oxygen reduction and evolution catalysts that can be easily integrated into existing devices is crucial for the wide deployment of energy storage systems that utilize O 2 -H 2 O chemistries, such as regenerative fuel cells and metal-air batteries. Herein, we report an NH 3 -activated N-doped hierarchical carbon (NHC) catalyst synthesized via a scalable route, and demonstrate its device integration. The NHC catalyst exhibited good performance for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), as demonstrated by means of electrochemical studies and evaluation when integrated into the oxygen electrode of a regenerative fuel cell. The activities observed for both the ORR and the OER were comparable to those achieved by state-of-the-art Pt and Ir catalysts in alkaline environments. We have further identified the critical role of carbon defects as active sites for electrochemical activity through density functional theory calculations and high-resolution TEM visualization. As a result, this work highlights the potential of NHC to replace commercial precious metals in regenerative fuel cells and possibly metal-air batteries for cost-effective storage of intermittent renewable energy.

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

Direct CO 2 Reduction to CO with an Fe 4 S 4 -Based Coordination Polymer

Fe 4 S 4 clusters play essential roles in nature, classically in electron transport but increasingly in newly discovered reactivity or catalysis. These roles have spurred interest in developing synthetic Fe 4 S 4 systems and while several molecular and material systems built from Fe 4 S 4 clusters have been developed, comparatively few examples of synthetic Fe 4 S 4 cluster-based catalysts exist. Herein, we present the use of an Fe 4 S 4 -based coordination polymer as a catalyst for the direct and selective electroreduction of CO 2 to CO. Computational studies suggest that the reaction proceeds through CO 2 binding to a reduced Fe 4 S 4 cluster, followed by a series of protonation, reduction, and H 2 O loss steps to yield a CO-bound cluster that can finally exchange with CO 2 to restart the catalytic cycle. CO bound clusters are predicted to be thermodynamically stable, suggesting that carbonyl species might be off-cycle intermediates. Mechanistic CV studies as well as in situ studies by IR spectroscopy provide evidence for carbonyl-ligated clusters, supporting these compounds as unusual examples of small molecule binding to Fe 4 S 4 clusters. Finally, this work establishes Fe 4 S 4 cluster-based coordination polymers as direct electrocatalysts for CO 2 reduction and provides mechanistic insights into how these species mediate catalytic conversions of small molecules.

cluster chemistry↗
DOE OSTI2022

Treatment of emerging contaminants in simulated wastewater via tandem photo-Fenton-like reaction and nutrient recovery

We report a tandem strategy that recovers NH 4 + and PO 4 3- nutrients from simulated wastewater in a solid form after the Fenton oxidation of emerging organic contaminants was developed. Mesoporous Cu–MgO nanoparticles were used as a photo-Fenton-like catalyst to oxidize paraoxon and tetracycline present in nutrient-rich simulated wastewater to prevent their incorporation into the struvite product. Mesoporous MgO nanoparticles were subsequently used as the Mg-source for the struvite crystallization due to the fast intraparticle diffusion and adsorption kinetics facilitated by their porosity and the high surface area. Without Fenton oxidation, 13% of paraoxon and 37% of tetracycline were incorporated into the struvite, demonstrating the clear need for the removal of hazardous contaminants before struvite synthesis. Both organic contaminants were eliminated using the Fenton oxidation reaction, with some minor non-toxic intermediate products formed. The product formed after the tandem process was shown by XRD and Raman spectroscopy to be struvite free of the emerging organic contaminants.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Fundamental understanding of oxygen reduction and reaction behavior and developing high performance and stable hetero-structured cathodes

New unique hetero-structured cathode has been developed in this project. La 2 NiO 4+δ (LNO) as a surface catalyst with interstitial oxygen defects was introduced onto the state-of-the-art (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathode to enhance the surface-limited ORR kinetics on SOFC cathode. Furthermore, the hetero-structured cathode surface maintains high activity under electrode polarization with much less negative effects from surface cation segregation of Sr, which is known to cause degradation issues for conventional LSCF and LSC cathodes, thus improving the cathode long-term stability. The interface chemistry distribution and oxygen transport properties have been studied to prove the enhancement of power out and stability of LNO-infiltrated LSCF cathode. The further investigation demonstrates that CeO 2 & La 2-x NiO 4+δ (x=0-0.2) co-infiltration is a simple and cost-effective method to improve both performance and stability of LSCF cathode by limiting nano-particles growth/delamination and further improve the surface stability. For the first time, a physical model is proposed to illustrate how unique interstitial species on hetero-structured cathode surface work to regulate the exchange rate of the incorporation reaction. Meanwhile, fundamental investigation of the surface oxygen exchange and bulk oxygen transport properties under over-potential conditions across cathode materials have been carried out in this project, which were discussed and compared to the Nernst equation that is generally applied to treat any oxide electrodes under equilibrium.

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

On-Demand Reactivity Enhancement to Enable Advanced Low Temperature Natural Gas Internal Combustion Engines

This research project set the groundwork for higher technology readiness level implementations of catalytic OCM pretreatment for NG engines. Future work to use OCM as a fuel pretreatment strategy for NG engines should consider catalyst durability and performance over a higher working temp range. Work should also develop robust and practical reactors that can be efficiently thermally integrated with a NG engine.

03 NATURAL GAS↗