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DOE OSTI2021

Copper carbon composite wire with a uniform carbon dispersion made by friction extrusion

Copper-carbon composites are a group of materials with excellent mechanical, electrical, thermal, and tribological properties. However, bulk size copper-carbon composites made by the traditional manufacturing processes, like rolling or extrusion, fall short of reaching some of these properties predicted by theory or demonstrated only by samples at centimeter scale or smaller. The two main challenges to the successful scaling-up are: 1) to uniformly disperse carbon in the metal matrix; 2) to avoid degradation due to oxidation or reaction from overheating. In this work, we first demonstrate friction extrusion as a new method to make bulk-size void-free copper-carbon composite wires with homogenized carbon dispersion. Three different carbon varieties, graphite powder, graphene nanopowder, and carbon nanotubes, were added to the copper matrix with the concentration ranging from 0.5 wt% to 15 wt%. Special tooling, processing parameters, and procedures were developed, especially for high carbon content samples. Ten-fold reductions of both copper grain size and carbon particle size were achieved and attributed to the high shear deformation. Energy dispersive X-ray spectrometry indicates the carbon powder was refined to a sub-micron level and uniformly dispersed in the copper matrix. Compared with that of pure copper, the thermal capacity of the composite wire increases by 30 % while density reduces by 29 %.

Friction extrusion, Metal matrix composite, Graphe↗

DOE OSTI2023

Coating developments towards enabling aluminum as a bipolar plate material for PEM fuel cells

Bipolar plates represent a significant portion of the cost and weight of a proton exchange membrane fuel cell stack. As a result, there has been significant interest in using low weight and cost materials, such as aluminum. Aluminum has good mechanical and physical properties; however, it performs poorly in the corrosive environment within the fuel cell stack. To overcome the corrosion performance issue, there have been efforts towards developing coating processes to enable aluminum to attain corrosion targets. In an effort to enable aluminum as a viable bipolar plate material, a solid phase processing (diffusion bonding) approach for bonding a titanium foil to aluminum is investigated in this study. The microstructure, corrosion performance, mechanical properties and electrical resistance are investigated. To avoid the known reduction in contact resistance performance of titanium after exposure to bipolar plate media, the effect of addition of highly conductive gold particles after diffusion bonding, on contact resistance and corrosion behavior, is also studied and compared with diffusion bonded Ti to Al. In conclusion, the results indicate that diffusion bonded Ti to Al provides a viable alternative material combination for bipolar plate that avoids the micro pores and crevasses that are associated with vapor deposition or electroplating.

25 ENERGY STORAGE↗

DOE OSTI2022

Integration of high confinement, high poloidal beta plasma with dual radiated power and detachment controls for divertor protection and ELM suppression

Divertor detachment without serious core confinement quality loss in DIII-D’s high poloidal β scenario has been combined with impurity-induced ELM mitigation without disruption. Use of Ne previously granted access to a detached, non-ELMing regime that retained high confinement quality due to stimulation of Internal Transport Barrier (ITB) growth, but suffered from on-going core fuel dilution and high disruptivity. Excess Ne accumulation in the core plasma has now been avoided by feeding back core radiated power ($P_{rad}$) measurements to control Ne seeding, rather than using attachment fraction ($A_{frac}$) control with Ne; this also reduces disruptivity. At the same time, N 2 seeding is used in a feedback loop with $A_{frac}$ measurements, which previously posed low disruption risk. In this way, the effect of Ne in the core is managed while avoiding excess seeding, and N 2 acts to correct for any excess heat exhaust that might interfere with detachment. The average Ne flow rate was 38% of what was used in pure Ne $A_{frac}$ control, plus average N 2 flow that was 43% of pure N 2 $A_{frac}$ control, even while meeting an even deeper detachment target. Meanwhile, a steep pressure gradient in the core plasma reduces sensitivity to impurity-induced degradation of the pedestal and reasonable confinement quality was maintained despite operational challenges that blocked formation of an ITB in these experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Techno-economic analysis of renewable energy generation at the South Pole

Transitioning from fossil-fuel power generation to renewable energy generation and energy storage in remote locations has the potential to reduce both carbon emissions and cost. Here, this study presents a techno-economic analysis for implementation of a hybrid renewable energy system at the South Pole in Antarctica, which currently hosts several high-energy physics experiments with nontrivial power needs. A tailored model of resource availability and economics for solar photovoltaics, wind turbine generators, lithium-ion energy storage, and long-duration energy storage at this site is explored in different combinations with and without existing diesel energy generation. The Renewable Energy Integration and Optimization (REopt) platform is used to determine the optimal system component sizing and the associated system economics and environmental benefit. We find that the least-cost system includes all three energy generation sources and lithium-ion energy storage. For an example steady-state load of 170 kW, this hybrid system includes 180 kW-DC of photovoltaic panels, 570 kW of wind turbines, and a 3.4 MWh lithium-ion battery energy storage system. This system reduces diesel consumption by 95% compared to an all -diesel configuration, resulting in approximately 1200 metric tons of carbon footprint avoided annually. Over the course of a 15-year analysis period the reduced diesel usage leads to a net savings of 57 million United States dollars, with a time to payback of approximately two years. All the scenarios modeled show that the transition to renewables is highly cost effective under the unique economics and constraints of this extremely remote site.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2025

A techno-economic assessment of carbon dioxide removal pathways via biochemical conversion of lignocellulose to biofuels and bioplastics

Biomass carbon removal and storage (BiCRS) is a promising pathway to mitigate climate change via large scale removal of atmospheric carbon dioxide (CO 2 ). We modeled several fermentation technologies, producing a variety of bioproducts from lignocellulosic feedstocks, to understand their levelized cost of CO 2 removal under multiple scenarios. Lifecycle greenhouse gas (GHG) emissions are accounted to provide cradle-to-grave estimates of carbon intensity (CI). We did not account for the avoided fossil CO 2 emissions from the use of biofuels in our CO 2 removal cost calculations, because avoided emissions do not contribute to CO 2 removal. The main products from the fermentation technologies we modeled include renewable diesel, ethanol, sustainable aviation fuel (SAF), and polyethylene (PE), with co-products including CO 2 , adipic acid, steam, and electricity. PE, depending on its end-of-life management, can serve as a form of biogenic carbon storage. PE has the potential to remove 1.2–1.5 tCO 2 per dry t-biomass, whereas biofuels have the potential to remove 0.3–0.9 tCO 2 per dry t-biomass, indicating that PE production is a more efficient method of carbon removal. We quantify costs of CO 2 removal to be $\$$60 – $\$$675 per metric tCO 2 removed across the various fermentation pathways. Under the scenarios analyzed, bioplastic production from lignocellulosic biomass is a more cost-effective route to CO 2 removal than biofuel production, with costs of CO 2 removal via bioplastics being 50–90 % lower than that of biofuels. Future research should explore the potential benefits and drawbacks of expanding bioplastic production for large-scale CO 2 removal.

09 BIOMASS FUELS↗

DOE OSTI2021

Techno-economic-environmental impacts of industrial energy assessment: Sustainable industrial motor systems of small and medium-sized enterprises

Energy assessments can provide an effective way of identifying and implementing energy efficiency measures to save energy costs and avoid emissions throughout manufacturing facilities. Consequently, it generates significant economic and environmental benefits to localities, states, and the nation. Quantifying these benefits requires a systematic techno-economic-environmental framework for capturing the interactions. This article employs methodologies to improve the energy efficiency of small and medium-size industries through their sustainable industrial motor systems. Motor systems offer large opportunities to enhance energy efficiency through adopting advanced technologies and better-informed operations. Case studies presented illuminate the potential savings and impacts from implementing sustainable motor systems and the importance of energy assessments. Here, the integrated macro-economic analysis quantifies the regional sustainability impacts of implementing the industrial energy efficiency offered by an energy auditing program in Ohio over a ten-year period. Results show that implementing all the center’s motor recommendations have directly saved $\$702$ M in energy costs, avoided 2.7 million metric tons of carbon dioxide emissions, and created 3,445 jobs, resulting in a total annual economic impact of $\$788$ M stemming from direct, indirect, and induced regional economic impacts. It provides policy implications for encouraging sustainable industrial motor systems.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Role of climate goals and clean-air policies on reducing future air pollution deaths in China: a modelling study

Over 3 million people still die every year from diseases caused by exposure to outdoor PM 2.5 air pollution, and more than a quarter of these premature deaths occur in China. In addition to clean air policies that target pollution emissions, climate policies aimed at reducing fossil-fuel CO 2 emissions (e.g., to avoid 1.5°C of warming) may also dramatically improve air quality and public health. Yet there has been no comprehensive accounting of public health outcomes under different energy pathways and local clean air management decisions in China. In particular, further research is needed to understand the relationships among climate and clean air polices and future health burdens in China, where an aging population will further exacerbate the impacts of air pollution. Using a China-focused integrated assessment model (GCAM-China) and a dynamic emission projection model (DPEC), we project future Chinese air quality in scenarios spanning a range of global climate targets (i.e. 1.5°0C, 2°C, NDC, unambitious, baseline, and 4.5°C) as well as national clean air actions (i.e. 2015-pollution, current-pollution, and ambitious-pollution). We then evaluate the health impacts of PM2·5 air pollution of scenario matrix using the chemical transport model WRF-CMAQ and the latest epidemiological concentration–response (C-R) functions (i.e. GBD2019). We find that, without ambitious climate mitigation (e.g., under current NDC pledges), Chinese deaths related the PM2.5 air pollution do not substantially decrease—and often grow—by mid-century, regardless of clean air policies and air quality improvements. For example, in scenarios that track China’s current NDC pledge and deploy best-available pollution control technologies, PM 2.5 -related deaths in China decrease slightly by 2030 (to 1.2 million per year) but no further by mid-century (Ambitious-pollution-NDC-goals; 1.2 million deaths in 2050) despite substantial and continuous improvements in population-weighted air quality (27.2 to 16.0 µg/m 3 from 2030 to 2050). The contrary trends of improving air quality and increasing PM 2·5 -related deaths in many of our scenarios reveals the extent to which extra efforts are needed to compensate for the established fact of increasing age of China’s population in future. Substantial decreases in China’s PM 2.5 -related deaths and age-standardized death rates (e.g., decreasing by 0.3–0.5 million deaths and 10.2–14.2 per 100,000 population age-standardized death rates per year) thus require the sort of large-scale transition in energy sources entailed by scenarios that meet international climate goals to avoid 1.5°C and 2°C of warming (Ambitious-pollution-2°C- and 1.5°C-goals).

58 GEOSCIENCES↗

DOE OSTI2020

Electrochemical Oxidation of Organic Molecules at Lower Overpotential: Accessing Broader Functional Group Compatibility with Electron-Proton Transfer Mediators

CONSPECTUS: Electrochemical organic oxidation reactions are highly appealing because protons are often effective terminal electron acceptors, thereby avoiding undesirable stoichiometric oxidants. These reactions are often plagued by high overpotentials, however, that greatly limit their utility. Single-electron transfer (SET) from organic molecules generates high energy radical-cations. Formation of such intermediates often requires electrode potentials far above the thermodynamic potentials of the reaction and frequently causes decomposition and/or side reactions of ancillary functional groups. In this Account, we show how electrocatalytic electron-proton transfer mediators (EPTMs) address this challenge. EPTMs bypass the formation of radical-cation intermediates by supporting mechanisms that operate at electrode potentials much lower (=1 V) than analogous direct electrolysis reactions. The stable aminoxyl radical TEMPO (2,2,6,6-tetramethylpiperidine N-oxyl) is an effective mediator for electrochemical alcohol oxidation, and we have employed such processes for applications ranging from pharmaceutical synthesis to biomass conversion. A complementary electrochemical alcohol oxidation method employs a cooperative Cu/TEMPO mediator system that operates at 0.5 V lower electrode potential than the TEMPO-only mediated process. This difference, which arises from a different catalytic mechanism, rationalizes the broad functional group tolerance of Cu/TEMPO-based aerobic alcohol oxidation catalysts. Aminoxyl mediators address long-standing challenges in the "Shono oxidation", an important method for a-C–H oxidation of tertiary amides and carbamates. Shono oxidations are initiated by a high-potential SET step that limits their utility. Aminoxyl-mediated Shono-type oxidations have been developed that operate at much lower potentials and tolerate diverse functional groups. Analogous reactivity underlies a-C–H cyanation of secondary cyclic amines, a new method that enables efficient diversification of piperidine-based pharmaceutical building blocks and preparation of non-natural amino acids. Electrochemical oxidations of benzylic C–H bonds are commonly initiated by SET to generate radical cations, but such methods are again plagued by large overpotentials. Mediated electrolysis methods that promote hydrogen-atom-transfer (HAT) from benzylic C–H bonds to Fe-oxo species and phthalimide N-oxyl (PINO) support C–H oxygenation, iodination, and oxidative-coupling reactions. A complementary method merges photochemistry with electrochemistry to achieve amidation of C(sp3)–H bonds. This unique process operates at much lower overpotentials compatible with diverse functional groups. These results have broad implications for organic electrochemistry, highlighting the importance of "overpotential" considerations and the prospects for expanding synthetic utility by using mediators to bypass high-energy outer-sphere electron-transfer mechanisms. Principles demonstrated here for oxidation are equally relevant to electrochemical reductions.

Wang, Fei↗

DOE OSTI2024

Impact of Sr-Containing Secondary Phases on Oxide Conductivity in Solid-Oxide Electrolyzer Cells

Solid-oxide electrolyzer cells (SOECs) based on a yttria-stabilized zirconia (YSZ) oxide electrolyte produce hydrogen from water with the assistance of excess thermal energy; however, Sr diffusion within the Gd-doped CeO 2 (GDC) barrier layer during processing or operation can lead to the formation of unwanted secondary phases such as SrO and SrZrO 3 . Here, to establish and compare the degree of impact of these phases on SOEC performance, we conduct first-principles calculations to study their bulk oxide conductivities and compare them to that of the YSZ electrolyte. We find that SrO has a low conductivity arising from the poor mobility and low concentration of mobile oxygen vacancies, and its presence in SOECs should therefore be avoided. SrZrO 3 also has a lower oxide conductivity than YSZ; however, this discrepancy is primarily due to lower vacancy concentrations rather than low mobility. We find that sufficient levels of Y-doping on the Zr site can increase oxygen vacancy concentrations in SrZrO 3 to achieve an oxide ionic conductivity on par with that of YSZ, thereby mitigating any potential deleterious effect on transport performance. Energy-dispersive X-ray spectroscopy confirms that Y is the most common minority element present in SrZrO 3 forming near the GDC–YSZ interface, alleviating concerns regarding the impact of SrZrO 3 on device performance. These results from our combined computational–experimental analysis can inform future engineering strategies designed to limit the detrimental effects of Sr-induced secondary phase formation on SOEC performance.

08 HYDROGEN↗

DOE OSTI2021

Multiobjective Dynamic Optimization for Optimal Load-Following of Natural Gas Combined Cycle Power Plants under Stress Constraints

With the increasing penetration of intermittent renewable energy sources into the electric grid, there is an associated need for conventional thermal power plants that are designed to operate at base-load conditions to cycle their load rapidly and frequently and operate under low-load conditions. Fast load-following operations lead to plant efficiency loss and the reduction of equipment life. A high-fidelity dynamic model of a natural gas combined cycle power plant, with rigorous equipment level submodels, is developed to capture the plant transient performance and the thermomechanical stress evolution at the high-pressure drum is computed to assess the drum life consumption. Stress evolution is modeled for the location of the edge at the drum/downcomer junction that experiences high circumferential stress amplitude during the fast load-following operation, leading to higher fatigue damage than locations considered under existing design standards. A dynamic optimization problem is solved for optimal load-following operation. Depending on the value of the stress constraint and the desired ramp rate, satisfying the desired stress constraint may be infeasible without relaxing the ramp rate. A multiobjective dynamic optimization problem is solved using a lexicographic approach that minimizes ramp rate relaxation and maximizes efficiency while satisfying stress constraints, avoiding spraying to saturation, and maintaining main steam and reheat steam temperature within bounds. It was observed that the optimal ramp rate can be highly nonlinear as opposed to the industry-standard linear ramp rate. Nonlinear optimal ramp-rate profiles not only help to avoid stress constraints that may be unavoidable by using the linear profile but also result in higher efficiency than the linear profile. Furthermore, the study shows that there is a strong tradeoff between the relaxation in the plant ramp rate and the time-average thermal efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

A Note to Reviewers Suggesting Post-reaction Catalyst Characterization: Know What You’re Asking For

Here, we highlight examples of post-reaction characterization in thermo- and electrocatalysis to present the challenges in obtaining reliable data to answer specific questions about the true identity of the active site and/or catalyst deactivation/degradation. We use this editorial to suggest to reviewers that, when formulating comments to authors that involve materials characterization after reaction testing, they should consider what specific, meaningful information can be attained or what targeted question can be answered that adds value to the individual paper and to the field in general, and how to reasonably obtain that data. In contrast, reviewers should avoid vague, open-ended comments that suggest unguided post-reaction characterization that would not add significant value to the report and, similarly, avoid comments that are substantial enough that they could form the basis of an entirely separate report.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Diabatic Valence-Hole Concept

A global diabatization scheme, based on the “valence-hole” concept, has been previously applied to model webs of avoided crossings that exist in four electronic-state symmetry manifolds of C 2 ( 1 Π g , 3 Π g , 1 Σ u + , and 3 Σ u + ). Here, this model is extended to the electronically excited states of four more molecules: CN ( 2 Σ + ), N 2 ( 3 Π u ), SiC ( 3 Π), and Si 2 ( 3 Π g ). Many strangenesses in the spectroscopic observations (e.g., energy level structure, predissociation linewidths, and radiative lifetimes) for all four electronic state systems discussed here are accounted for by this unified model. The key concept of the model is valence-hole electron configurations: 3σ 2 4σ 1 1π 4 5σ 2 in CN ( 2 Σ + ), 2σ g 2 2σ u 1 1π u 4 3σ g 2 1π g 1 in N 2 ( 3 Π u ), 5σ 2 6σ 1 7σ 2 2π 3 in SiC ( 3 Π), and 4σ g 2 4σ u 1 5σ g 2 2π u 3 in Si 2 ( 3 Π g ), all of which have a triply occupied “valence-core” (i.e., 2σ g 2 2σ u 1 or the equivalent). These valence-hole configurations have a nominal bond order of three or higher and correlate with high-energy separated-atom limits with an np ← ns (n = 2, 3) promotion in one of the atomic constituents. On its way to dissociation, the strongly bound diabatic valence-hole state crosses multiple weakly bound or repulsive states, which belong to electron configurations with a completely filled valence-core. These curve crossings between diabatic potentials result in a network of many avoided crossings among multiple electronic states, analogous to the well-studied electronic structure landscape of ionic-covalent crossings in strongly ionic molecules. In conclusion, considering the unique role of valence-hole states in shaping the global electronic structure, the valence-hole concept should be added to our intuitive framework of chemical bonding.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Hybrid Integration of GaP Photonic Crystal Cavities with Silicon-Vacancy Centers in Diamond by Stamp-Transfer

Optically addressable solid-state defects are emerging as some of the most promising qubit platforms for quantum networks. Maximizing photon-defect interaction by nanophotonic cavity coupling is key to network efficiency. We demonstrate fabrication of gallium phosphide 1-D photonic crystal waveguide cavities on a silicon oxide carrier and subsequent integration with implanted silicon-vacancy (SiV) centers in diamond using a stamp-transfer technique. The stamping process avoids diamond etching and allows fine-tuning of the cavities prior to integration. After transfer to diamond, we measure cavity quality factors (Q) of up to 8900 and perform resonant excitation of single SiV centers coupled to these cavities. For a cavity with a Q of 4100, we observe a 3-fold lifetime reduction on-resonance, corresponding to a maximum potential cooperativity of C = 2. In conclusion, these results indicate promise for high photon-defect interaction in a platform which avoids fabrication of the quantum defect host crystal.

Purcell enhancement↗

DOE OSTI2026

Strategy for Ultranarrow Light Down-Conversion for Displays Based on Bicolor-Emitting 2D Colloidal Heterostructures

The demand for ultranarrow spectral emission below 10 nm is critical for next-generation displays. Although current colloidal nanocrystals are successful in light down-conversion applications, they fall short in matching the stringent color purity requirements set by standards like Rec. 2020. Achieving such narrow linewidths through material engineering alone remains elusive, necessitating innovative light management strategies that avoid optical losses and maintain device efficiency. Here, in this work, we present a novel 2D colloidal heterostructure design, combining a CdSe core nanoplatelet, a CdS crown, and a CdZnS shell, to achieve bright bicolor emission in the solid state (green/red) emission with tunable intensity ratios controlled by excitation power (either optical or electrical). Integration of these nanoplatelets into a dielectric cavity further narrows the emission linewidth to sub-2 nm while enhancing the photoluminescence intensity by up to 200 times, meeting the Rec. 2020 color purity targets. This approach paves the way for a strategy avoiding complex laser-based solutions.

2D nanocrystals↗

DOE OSTI2023

Fine-Tuning of Pt Dispersion on Al 2 O 3 and Understanding the Nature of Active Pt Sites for Efficient CO and NH 3 Oxidation Reactions

Fine-tuning the dispersion of active metal species on widely used supports is a research hotspot in the catalysis community, which is vital for achieving a balance between the atomic utilization efficiency and the intrinsic activity of active sites. In this work, using bayerite Al(OH) 3 as support directly or after precalcination at 200 or 550 °C, Pt/Al 2 O 3 catalysts with distinct Pt dispersions from single atoms to clusters (ca. 2 nm) were prepared and evaluated for CO and NH 3 removal. Richer surface hydroxyl groups on AlO x (OH) y support were proved to better facilitate the dispersion of Pt. However, Pt/Al 2 O 3 with relatively lower Pt dispersion could exhibit better activity in CO/NH 3 oxidation reactions. Further reaction mechanism study revealed that the Pt sites on Pt/Al 2 O 3 with lower Pt dispersion could be activated to Pt 0 species much easier under the CO oxidation condition, on which a higher CO adsorption capacity and more efficient O 2 activation were achieved simultaneously. Compared to Pt single atoms, PtO x clusters could also better activate NH 3 into –NH 2 and –HNO species. The higher CO adsorption capacity and the more efficient NH 3 /O 2 activation ability on Pt/Al 2 O 3 with relatively lower Pt dispersion well explained its higher CO/NH 3 oxidation activity. This study emphasizes the importance of avoiding a singular pursuit of single-atom catalyst synthesis and instead focusing on achieving the most effective Pt species on Al 2 O 3 support for targeted reactions. Finally, this approach avoids unnecessary limitations and enables a more practical and efficient strategy for Pt catalyst fabrication in emission control applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

A Perspective on Thin-Film Perovskites as Supports for Metal Catalysts

Perovskite-supported metals have sometimes been referred to as “intelligent catalysts” because of the potential to regenerate sintered particles by driving the metal into the oxide lattice by high-temperature oxidation and releasing the metal by reduction. However, low surface areas and incomplete release of metal from the lattice have prevented the widespread application of these materials. Furthermore, we describe the preparation of thin perovskite films on stable supports by Atomic Layer Deposition (ALD) as a means for avoiding the limitations associated with bulk perovskites. Examples will be given that demonstrate many of the favorable properties of perovskite supports can be retained, while avoiding some of the shortcomings. Potential opportunities for using these materials are discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Discovering Ni/Cu Single-Atom Alloy as a Highly Active and Selective Catalyst for Direct Methane Conversion to Ethylene: A First-Principles Kinetic Study

Direct methane conversion to liquid fuels or value-added chemicals is a promising technology to utilize natural resources without resorting to further petroleum extraction. However, discovering efficient catalysts for this reaction is challenging due to either coke formation or unfavorable C-H bond activation. Herein, we design single-atom alloy (SAA) catalysts to simultaneously eliminate the above two bottlenecks based on mechanism-guided strategies: (1) the active single atom enables favorable C-H bond breaking and (2) the less reactive host metal facilitates C-C coupling and thus avoids strong binding of carbonaceous species. Employing electronic structure theory calculations, we screened the stability of multiple SAAs with 3d-5d transition metals atomically dispersed on a copper surface in terms of avoiding dopant aggregation and segregation. We then evaluated reactivities of the stable SAAs as catalysts for direct methane conversion to C2 products, including methane dehydrogenation and C-C coupling mechanisms. Combining selectivity analysis with kinetic modeling, we predicted that nickel dispersed on copper, i.e., Ni/Cu SAA, is a highly active and selective catalyst that can efficiently transform methane to ethylene. This work designs efficient SAA catalysts for direct methane activation and provides chemical insights into engineering compositions of SAAs to tune their catalytic performances.

Kothakonda, Manish↗

DOE OSTI2022

Techno-economic Analysis and Life-Cycle Analysis of Renewable Diesel Fuels Produced with Waste Feedstocks

Wet waste feedstocks represent an important category of resources that could be utilized to produce biofuels. Diversion of the wet waste resources from going through conventional waste management practices to utilization as feedstocks for energy production also benefits from avoided cost and pollutant emissions of waste management and disposal. This study investigates the economic and environmental implications of producing bio-blendstocks for mixing controlled compression ignition (MCCI) engines from two waste-to-fuel pathways: hydroprocessed esters and fatty acids (HEFA) from yellow grease, and swine manure hydrothermal liquefaction (HTL) followed by biocrude upgrading. Detailed process models were developed for both pathways, which informed the techno-economic analysis (TEA) and life-cycle analysis (LCA). Conventional swine manure management practice was also modeled in detail as the business-as-usual (BAU) scenario for the swine manure HTL pathway. The estimated minimum fuel selling prices (MFSP) were $4.47/gasoline gallon equivalent (GGE) and $3.57/GGE for the yellow grease to HEFA and swine manure HTL pathways, respectively. The life-cycle greenhouse gas (GHG) emissions of the two pathways were 11.2 and -33.3 g CO2e/MJ, respectively, for the yellow grease to HEFA and swine manure HTL pathways. The credits of avoided emissions from conventional swine manure management were the main reason for the negative GHG emissions of the swine manure HTL pathway. The marginal GHG emissions abatement costs were estimated to be $100 – $253/tonne CO2e and $5 – $103/tonne CO2e for the yellow grease HEFA and swine manure HTL pathways, respectively, for a diesel price ranging between $2.0/GGE and $3.5/GGE. Since the yellow grease HEFA pathway is already commercialized, it can benefit from the $200/tonne carbon credit in the California Low Carbon Fuel Standard (LCFS) market, which could help the yellow grease HEFA pathway to achieve near-zero marginal GHG emissions abatement cost.

renewable diesel, techno economic analysis, life c↗