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At least 271 records · Page 15

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DOE OSTI2023

Designing High‐Donicity Anions for Rechargeable Potassium Superoxide/Peroxide Batteries

Abstract A battery cathode based on the superoxide/peroxide redox not only inherits the advantage of oxygen (O 2 ) batteries in high capacities and low costs but also overcomes the disadvantages in O 2 storage, electrolyte evaporation, and anode deactivation due to O 2 crossover. Herein, we report an enhanced potassium superoxide (KO 2 )/peroxide (K 2 O 2 ) conversion by adopting a high‐donicity anion additive in the ether‐based electrolyte. Such an anion was synthesized via a “Solvent‐in‐Anion” strategy and validated to enhance the electron donicity of the electrolyte. The use of high‐donicity anion could lead to enhanced KO 2 utilization (≈90.2 %) by retarding electrode passivation and allow the full charging back of K 2 O 2 through the solution‐mediated pathway without electrocatalysts. No apparent cell degradation is observed during the first 120 cycles by controlling the reversible depth‐of‐discharge capacity at 292 mAh g −1 within an O 2 ‐free region. The K−KO 2 cell delivers a high energy efficiency (>84.4 %) and a lifespan of over 1440 hours.

Qin, Lei↗

DOE OSTI2023

Rapid Polyolefin Hydrogenolysis by a Single‐Site Organo‐Tantalum Catalyst on a Super‐Acidic Support: Structure and Mechanism

Abstract The novel electrophilic organo‐tantalum catalyst AlS/TaNp x ( 1 ) (Np=neopentyl) is prepared by chemisorption of the alkylidene Np 3 Ta=CH t Bu onto highly Brønsted acidic sulfated alumina (AlS). The proposed catalyst structure is supported by EXAFS, XANES, ICP, DRIFTS, elemental analysis, and SSNMR measurements and is in good agreement with DFT analysis. Catalyst 1 is highly effective for the hydrogenolysis of diverse linear and branched hydrocarbons, ranging from C2 to polyolefins. To the best of our knowledge, 1 exhibits one of the highest polyolefin hydrogenolysis activities (9,800 (CH 2 units) ⋅ mol(Ta) −1 ⋅ h −1 at 200 °C/17 atm H 2 ) reported to date in the peer‐reviewed literature. Unlike the AlS/ZrNp 2 analog, the Ta catalyst is more thermally stable and offers multiple potential C−C bond activation pathways. For hydrogenolysis, AlS/TaNp x is effective for a wide variety of pre‐ and post‐consumer polyolefin plastics and is not significantly deactivated by standard polyolefin additives at typical industrial concentrations.

Lai, Qingheng↗

DOE OSTI2024

Steam‐Assisted Selective CO 2 Hydrogenation to Ethanol over Ru−In Catalysts

Abstract Multicomponent catalysts can be designed to synergistically combine reaction intermediates at interfacial active sites, but restructuring makes systematic control and understanding of such dynamics challenging. We here unveil how reducibility and mobility of indium oxide species in Ru‐based catalysts crucially control the direct, selective conversion of CO 2 to ethanol. When uncontrolled, reduced indium oxide species occupy the Ru surface, leading to deactivation. With the addition of steam as a mild oxidant and using porous polymer layers to control In mobility, Ru−In 2 O 3 interface sites are stabilized, and ethanol can be produced with superior overall selectivity (70 %, rest CO). Our work highlights how engineering of bifunctional active ensembles enables cooperativity and synergy at tailored interfaces, which unlocks unprecedented performance in heterogeneous catalysts.

Zhou, Chengshuang↗

DOE OSTI2020

Redox Stability Controls the Cellular Uptake and Activity of Ruthenium-Based Inhibitors of the Mitochondrial Calcium Uniporter (MCU)

The mitochondrial calcium uniporter (MCU) is the ion channel that mediates Ca 2+ uptake in mitochondria. Inhibitors of the MCU are valuable as potential therapeutic agents and tools to study mitochondrial Ca 2+ . The best-known inhibitor of the MCU is the ruthenium compound Ru360. Although this compound is effective in permeabilized cells, it does not work in intact biological systems. We have recently reported the synthesis and characterization of Ru265, a complex that selectively inhibits the MCU in intact cells. In this work, the physical and biological properties of Ru265 and Ru360 are described in detail. Using atomic absorption spectroscopy and X-ray fluorescence imaging, we show that Ru265 is transported by organic cation transporter 3 (OCT3) and taken up more effectively than Ru360. As an explanation for the poor cell uptake of Ru360, we show that Ru360 is deactivated by biological reductants. These data highlight how structural modifications in metal complexes can have profound effects on their biological activities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Zeolite-Stabilized Di- and Tetranuclear Molybdenum Sulfide Clusters Form Stable Catalytic Hydrogenation Sites

Supercages of faujasite (FAU)-type zeolites serve as a robust scaffold for stabilizing dinuclear (Mo 2 S 4 ) and tetranuclear (Mo 4 S 4 ) molybdenum sulfide clusters. The FAU-encaged Mo 4 S 4 clusters have a distorted cubane structure similar to the FeMo-cofactor in nitrogenase. Both clusters possess one unpaired electron per Mo atom. Additionally, they show identical catalytic activity per sulfide cluster. Their catalytic activity is stable (> 150 h) for ethene hydrogenation, while layered MoS 2 structures deactivate significantly under the same reaction conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Metal-like Charge Transport in PEDOT(OH) Films by Post-processing Side Chain Removal from a Soluble Precursor Polymer

Herein, a route to produce highly electrically conductive doped hydroxymethyl functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) films, termed PEDOT(OH) with metal-like charge transport properties using a fully solution processable precursor polymer is reported. Further, this is achieved via an ester-functionalized PEDOT derivative [PEDOT(EHE)] that is soluble in a range of solvents with excellent film-forming ability. PEDOT(EHE) demonstrates moderate electrical conductivities of 20–60 S cm -1 and hopping-like (i.e., thermally activated) transport when doped with ferric tosylate (FeTos 3 ). Upon basic hydrolysis of PEDOT(EHE) films, the electrically insulative side chains are cleaved and washed from the polymer film, leaving a densified film of PEDOT(OH). These films, when optimally doped, reach electrical conductivities of ≈1200 S cm -1 and demonstrate metal-like (i.e., thermally deactivated and band-like) transport properties and high stability at comparable doping levels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Modelling Development in Radical (Co)Polymerization of Multivinyl Monomers

Radical polymerization (RP) of multivinyl monomers (MVMs) provides a facile solution for manipulating polymer topology and has received increasing attention due to their industrial and academic significance. Continuous efforts have been made to understand their mechanism, which is the key to regulating materials structure. Modelling techniques have become a powerful tool that can provide detailed information on polymerization kinetics which is inaccessible by experiments. Many publications have reported the combination of experiments and modelling for free radical polymerization (FRP) and reversible-deactivation radical polymerizations (RDRP) of MVMs. Herein, a minireview is presented for the most important modelling techniques and their applications in FRP/RDRP of MVMs. This review hopes to illustrate that the combination of modelling and wet experiments can be a great asset to polymer researchers and inspire new thinking for the future MVMs experiment optimization and product design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Designing High‐Donicity Anions for Rechargeable Potassium Superoxide/Peroxide Batteries

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Rapid Polyolefin Hydrogenolysis by a Single‐Site Organo‐Tantalum Catalyst on a Super‐Acidic Support: Structure and Mechanism

The novel electrophilic organo-tantalum catalyst AlS/TaNp x (1) (Np=neopentyl) is prepared by chemisorption of the alkylidene Np 3 Ta=CH t Bu onto highly Brønsted acidic sulfated alumina (AlS). Here, the proposed catalyst structure is supported by EXAFS, XANES, ICP, DRIFTS, elemental analysis, and SSNMR measurements and is in good agreement with DFT analysis. Catalyst 1 is highly effective for the hydrogenolysis of diverse linear and branched hydrocarbons, ranging from C2 to polyolefins. To the best of our knowledge, 1 exhibits one of the highest polyolefin hydrogenolysis activities (9,800 (CH 2 units) ⋅ mol(Ta) −1 ⋅ h −1 at 200 °C/17 atm H 2 ) reported to date in the peer-reviewed literature. Unlike the AlS/ZrNp 2 analog, the Ta catalyst is more thermally stable and offers multiple potential C−C bond activation pathways. For hydrogenolysis, AlS/TaNp x is effective for a wide variety of pre- and post-consumer polyolefin plastics and is not significantly deactivated by standard polyolefin additives at typical industrial concentrations.

03 NATURAL GAS↗

DOE OSTI2024

Controlling the Phase Transformation of Alumina for Enhanced Stability and Catalytic Properties

Current transition alumina catalysts require the presence of significant amounts of toxic, environmentally deleterious dopants for their stabilization. Herein, we report a simple and novel strategy to engineer transition aluminas to withstand aging temperatures up to 1200 °C without inducing the transformation to low-surface-area α-Al 2 O 3 and without requiring dopants. By judiciously optimizing the abundance of dominant facets and the interparticle distance, we can control the temperature of the phase transformation from θ-Al 2 O 3 to α-Al 2 O 3 and the specific surface sites on the latter. These specific surface sites provide favorable interactions with supported metal catalysts, leading to improved metal dispersion and greatly enhanced catalytic activity for hydrocarbon oxidation. Further, the results presented herein not only provide molecular-level insights into the critical factors causing deactivation and phase transformation of aluminas but also pave the way for the development of catalysts with improved activity for catalytic hydrocarbon oxidation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Converting Carbon Dioxide into Carbon Nanotubes by Reacting with Ethane

In this study, the urgency to mitigate environmental impacts from anthropogenic CO 2 emissions has propelled extensive research efforts on CO 2 reduction. The current work reports a novel approach involving transforming CO 2 and ethane into carbon nanotubes (CNTs) using earth-abundant metals (Fe, Co, Ni) at 750 °C. This route facilitates long-term carbon storage via generating high-value CNTs and produces valuable syngas with adjustable H 2 /CO ratios as byproducts. Without CO 2 , direct pyrolysis of ethane undergoes rapid deactivation. The participation of CO 2 not only enhances the durability of the catalyst, but also contributes about 30 % of the CNTs production, presenting a viable solution to CO 2 challenges. The CNT morphology depends on the catalyst used. Co- and Ni-based catalysts produce CNT with a 20 nm diameter and micrometer length, whereas Fe-based catalysts yield bamboo-like structures. This work represents a pioneering effort in utilizing CO 2 and ethane for CNT production with potential environmental and economic benefits.

09 BIOMASS FUELS↗

DOE OSTI2024

Steam-Assisted Selective CO 2 Hydrogenation to Ethanol over Ru–In Catalysts

Multicomponent catalysts can be designed to synergistically combine reaction intermediates at interfacial active sites, but restructuring makes systematic control and understanding of such dynamics challenging. In this work, we unveil how reducibility and mobility of indium oxide species in Ru-based catalysts crucially control the direct, selective conversion of CO 2 to ethanol. When uncontrolled, reduced indium oxide species occupy the Ru surface, leading to deactivation. With the addition of steam as a mild oxidant and using porous polymer layers to control In mobility, Ru–In 2 O 3 interface sites are stabilized, and ethanol can be produced with superior overall selectivity (70 %, rest CO). Our work highlights how engineering of bifunctional active ensembles enables cooperativity and synergy at tailored interfaces, which unlocks unprecedented performance in heterogeneous catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

A Stable Site‐Isolated Mono(phosphine)‐Rhodium Catalyst on a Metal‐Organic Layer for Highly Efficient Hydrogenation Reactions

Abstract Phosphine‐ligated transition metal complexes play a pivotal role in modern catalysis, but our understanding of the impact of ligand counts on the catalysis performance of the metal center is limited. Here we report the synthesis of a low‐coordinate mono(phosphine)‐Rh catalyst on a metal‐organic layer (MOL), P‐MOL • Rh, and its applications in the hydrogenation of mono‐, di‐, and tri‐substituted alkenes as well as aryl nitriles with turnover numbers (TONs) of up to 390000. Mechanistic investigations and density functional theory calculations revealed the lowering of reaction energy barriers by the low steric hindrance of site‐isolated mono(phosphine)‐Rh sites on the MOL to provide superior catalytic activity over homogeneous Rh catalysts. The MOL also prevents catalyst deactivation to enable recycle and reuse of P‐MOL • Rh in catalytic hydrogenation reactions.

Chemistry↗

DOE OSTI2024

Fuel‐Driven π‐Conjugated Superstructures to Form Transient Conductive Hydrogels

Despite advances in creating dissipative materials with transient properties, such as hydrogels and active droplets, their application remains confined to temporal changes in structural properties. Developing out-of-equilibrium materials whose electronic functions are parameterized by a chemical reaction cycle is challenging. Yet, this class of materials is required to construct biomimetic materials. In contrast to traditional chemical reaction cycles that exploit molecularly dissolved building blocks at thermodynamic equilibrium, we show that fiber structures derived from reactive naphthalene diimide (NDI) building blocks can be used as resting states to form far-from-equilibrium conductive hydrogels after the addition of chemical fuels. Upon fueling the NDI-derived fibers, a dual-component activation and deactivation pathway is deduced by kinetic analysis and is absent when using a molecularly dissolved resting state. Investigating the solid-state morphologies of the structures formed throughout the fuel-driven reaction cycle using cryo-EM reveals that the resting thermodynamic fibers evolve to transient thicker fibrils and layered superstructures. We show that the transient redox-active hydrogels exhibit a nearly threefold increase in electrical conductivity upon fuel consumption before reverting to their original value over hours. In conclusion, these far-from-equilibrium materials are potential candidates in applications such as programmable biorobotics and chemical computing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Self‐Stabilized Heterometallic Pair Sites for Selective Ethanol Dehydrogenation on Pt–Cr–Ag Alloy Catalysts

Self‐stabilized, heterometallic pair‐sites can enable fine‐tuning of catalytic functionality while also mitigating dynamic structural changes that degrade catalytic performance. This study demonstrates the development and characterization of trimetallic Pt x Cr x Ag 1‐2x ( x ≤ 0.1) alloys with active Pt–Cr pair‐ensembles for non‐oxidative ethanol dehydrogenation, leveraging predictions that favorable bonding stabilizes Pt–Cr pairs diluted in Ag. Operando X‐ray absorption spectroscopy confirms the preferential formation and stability of Pt–Cr pairings dispersed throughout the Ag matrix, and ambient‐pressure X‐ray photoelectron spectroscopy shows that Pt–Cr sites have significant activity for ethanol dehydrogenation, while suppressing reaction processes that deactivate binary Pt–Ag and Cr–Ag alloys. This work demonstrates that stabilizing heterometallic pair sites within trimetallic alloys provides a new avenue for designing catalysts with discrete active sites that are durable and highly selective.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Half‐sandwich ruthenium complex with a very low overpotential and excellent activity for water oxidation under acidic conditions

Abstract Molecular catalysts are acknowledged for the ability to design reaction sites within well‐defined structures to achieve high catalytic activities. However, in many cases, molecular catalysts undergo structural changes to some other form(s), which are finally the real catalysts. Here, we report two half‐sandwich ruthenium complexes; [Ru([9]aneN3)(bpy)Cl] + 3 and [Ru([9]aneN3)(pic)OH 2 ] 2+ 4 , based on the macrocyclic 1,4,7‐triazacyclononane ([9]aneN3) ligand for water oxidation (WO). The two complexes have similar core but different ancillary ligands, which greatly affected their stability as well as activity for WO. Complex 3 retained high stability and excellent activity (turnover number [TON] = 1250) in chemical WO and first‐order reaction kinetics with respect to [Ce IV ] with a calculated rate constant ( k cat ) of 34.59 s −1 . Further, the complex demonstrated very low overpotential of ~210 mV in electrochemical WO. At an overpotential of only 400 mV, turnover frequency (TOF) of complex 3 was electrochemically estimated to be 131.2 s −1 . In contrast, complex 4 underwent picolinate ligand dissociation, as a deactivation pathway, to form the tri‐aqua derivative. Density functional theory (DFT) calculations are used to explain the dissociation mechanism of picolinate ligand in complex 4 , which happens through a stepwise dissociation mechanism.

Younus, Hussein A.↗

DOE OSTI2020

Effect of using a nitrogen atmosphere on enzyme hydrolysis at high corn stover loadings in an agitated reactor

A comprehensive review of the literature shows that enzyme hydrolysis efficiency decreases with increased solids loadings at constant enzyme:cellulose ratios for pretreated lignocellulosic substrates. In seeking a mechanistic explanation for this phenomenon, we found that a nitrogen atmosphere enhances enzyme hydrolysis and minimizes the decrease in glucose yields as solids loadings are increased in an agitated bioreactor. Further, for liquid hot water pretreated corn stover, at solids loadings of both 100 and 200 g/L and hydrolyzed for 72 hr in a 1 L bioreactor at pH 5.0 with 3.6 mg protein per g biomass, glucose yields were 55% in a nitrogen atmosphere versus 45% in air with agitation and about 34% without agitation. While mixing promotes biomass/enzyme contact and disperses sugars released during hydrolysis that would otherwise cause product inhibition, nitrogen gas displaces air, avoiding deactivation of cellulases by oxygen. The nitrogen effect points to a facile approach of enhancing hydrolysis at high solids loadings.

09 BIOMASS FUELS↗

DOE OSTI2021

Protective effects of non–catalytic proteins on endoglucanase activity at air and lignin interfaces

The manner in which added non-catalytic proteins during enzymatic hydrolysis of lignocellulosic substrates enhances hydrolysis mechanisms is not completely understood. Prior research has indicated that a reduction in the non-specific adsorption of enzymes on lignin, and deactivation of enzymes exposed to air–liquid interface provide rationale. This work investigated root causes including effects of the air–liquid interface on non-catalytic proteins, and effects of lignin on endoglucanase. Three different experimental designs and three variables (air–liquid interfacial area, the types of lignin (acid or enzymatic lignin), and the presence of non-enzymatic protein (bovine serum albumin [BSA] or soy proteins ) were used. The results showed that acid isolated lignin adsorbed almost all endoglucanase activity initially present in supernatant, independent of air interface conditions (25 or 250 ml flasks) with the presence of BSA preventing this effect. Endoglucanase lost 30%–50% of its activity due to an air–liquid interface in the presence of lignin while addition of non-enzymatic protein helped to preserve this enzyme's activity. Langmuir and Freundlich models applied to experimental data indicated that the adsorption increases with increasing temperature for both endoglucanase and BSA. Adsorption of the enzyme and protein were endothermic with an increase in entropy. Finally, these results, combined, show that hydrophobicity plays a strong role in the adsorption of both endoglucanase and BSA on lignin.

59 BASIC BIOLOGICAL SCIENCES↗