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DOE OSTI2021

Wafer-scale remote epitaxy of III-V semiconductors and applications

In conventional epitaxy of single-crystalline semiconductor materials, it is challenging to separate the grown layer with the substrate due to the strong bonding at the interface. Remote epitaxy is a recently discovered method to grow single-crystalline thin films on graphene, wherein the grown film can be exfoliated at the graphene interface to form freestanding membranes. Here, we present our recent development on remote epitaxy of III-V semiconductors. We show that directly growing 2D materials on III-V substrates as a remote epitaxy template is an ideal pathway that can eliminate transfer process-related defects and can realize wafer-scale process of remote epitaxy and substrate reuse. We present the strategies to grow 2D materials on the surface of III-V materials, which is much more challenging than thermally robust substrates such as SiO2/Si or sapphire. The nucleation of III-V on 2D material-coated III-V platforms via remote interaction is investigated both experimentally and theoretically. Lastly, we show advanced remote epitaxial platforms and optoelectronic applications enabled by remote epitaxy, and the capability to recycle the III-V substrates for repeated remote epitaxy and production of freestanding III-V thin films.

Kim, Hyunseok↗

DOE OSTI2020

10 MWE CDCL Large Pilot Plant – pre-FEED Study

Coal Direct Chemical Looping (CDCL) is an advanced oxy-combustion technology that has the potential to substantially reduce the energy penalty and the cost of electricity (COE) for coal-fired power generation with CO₂ capture. The Babcock & Wilcox Company (B&W) and The Ohio State University (OSU) have been collaborating on the development of an iron oxide oxygen-carrier based chemical looping technology for clean power generation with inherent carbon capture. In this process, coal is dried and pulverized prior to being transported into a moving-bed reducer. In the reducer, coal reacts with the oxygen-carrier particles, forming combustion byproducts, predominantly CO₂ and H₂O, while reducing the iron oxide oxidation state from Fe₂O₃ to a mixture of FeO and Fe. The reduced state particles are then transported to a combustor reactor and re-oxidized with air. Following the oxidation, the oxygen-carrier particles are regenerated, and a large amount of heat is released for steam production. The produced steam is sent to a turbine for electricity generation. Meanwhile, the CO₂–rich stream leaving the reducer is cooled, cleaned, and compressed for subsequent pipeline transportation and sequestration. By combining air separation and fuel conversion into a single system, the CDCL technology enables the intensification of oxy-combustion processes by eliminating the energy and cost intensive cryogenic air separation unit and thereby results in higher overall plant efficiencies and lower COE’s. The use of a moving-bed reducer results in high conversions of volatile hydrocarbons and high CO₂ purity, which reduces the cost of downstream CO₂ purification for sequestration or utilization. The Babcock & Wilcox Company in collaboration with The Ohio State University, Johnson & Matthey, The Electric Power Research Institute, and Dover Light & Power completed a Preliminary Front-End Engineering and Design (Pre-FEED) study of a 10 MWe coal-direct chemical looping (CDCL) pilot plant. The planned system is a modular 10 MWe CDCL large pilot facility consisting in 4 modules of 2.5 MWe each, working in parallel and to be hosted within the current structure at the City of Dover’s Municipal Power Plant. The CDCL system can achieve auto-thermal operation and includes a sub-critical steam cycle for power generation. The pilot system was designed to demonstrate full commercial operation at a reduced scale. The coal distribution per plan area is a representative slice of larger commercial arrangements. The system includes a CO₂ recycle system, but it does not include a compression system. The large pilot includes all the environmental control equipment and oxygen carrier and ash handling systems. As part of the project, the Team performed laboratory testing and carried out multiple pilot test campaigns to obtain design and performance information at the 250 kWth CDCL pilot facility at the Babcock & Wilcox Company’s Research Center. The Team demonstrated sustained operations at designed coal inputs, high coal conversion, high CO₂ purity, heat generation on the combustor, low carbon carryover between reactors and low particle attrition. Emissions generated in the reducer reactor were identified as SO₂ and NO x . The commercial manufacturing cost of oxygen carrier particle was evaluated by JM. A particle manufacturing report was generated and submitted to the DOE. Based on the results from the pilot tests and the pre-FEED design efforts, a techno-economic analysis was performed. The study shows that the CDCL process is a promising carbon-friendly technology capable of producing electricity with high efficiency. The estimated COE of the supercritical CDCL plant is $83.3 / MWh, which meets DOE’s target of less than 30% increase in COE when compared to a supercritical PC plant without CO₂ capture. This is the lowest among the existing carbon capture technologies (post-combustion and oxy-combustion) for fossil fuel power plant. CDCL is evaluated to be the most promising technology for carbon capture from the economic aspect.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2023

Sequential separation of battery electrode materials and metal foils in aqueous media

To recycle high-value lithium-ion battery components, it is imperative to efficiently separate electrode materials from current collector foils and to separate cathodes from anodes. This study investigates the delamination behaviors of cathodes and anodes from their respective current collectors in aqueous media. Whereas anode films can easily detach from copper foils in water, the delamination of cathode films does not exhibit the same behavior in water; instead, the cation exchange reaction results in lithium leaching and aluminum corrosion in the presence of water. Here, a buffer solution with surfactant additives has been designed to prevent aluminum corrosion and to improve solution wetting behavior, thereby facilitating cathode delamination. The delamination difference enables the sequential recovery of electrode materials and metal foils at different separation stages, simplifying the traditionally intricate processes within a one-pot recovery system. The recovered materials retain their crystal structure and morphology, and there are no signs of aluminum corrosion or residues on the metal foils. The sequential separation technique achieves nearly 100% separation efficiency for electrode materials from metal foils and over 98% separation efficiency for cathode and anode materials.

25 ENERGY STORAGE↗

DOE OSTI2023

Unlocking the value of recycling scrap from Li-ion battery manufacturing: Challenges and outlook

The growing global trend toward mobile electrification is primarily driven by the rising popularity of electric vehicles, leading to an unprecedented surge in demand for lithium-ion batteries. As a result, the importance of battery recycling has become increasingly apparent. Battery recycling aims to recover valuable materials from both spent batteries and battery manufacturing scraps. By recycling these resources, the reliance on raw material extraction is reduced, which benefits resource conservation and minimizes the need for new mining operations. While significant attention has been given to the recycling of spent batteries, less emphasis has been placed on the recycling and recovery of battery scraps. However, it is important to recognize that many gigafactories are still taking steps to improve their manufacturing processes, and end-of-life batteries take approximately 10 years to become suitable for recycling, the manufacturing scraps will serve as the primary sources for recycling in this decade. This review delves into the progress in recycling technologies associated with battery manufacturing scraps, shedding light on the challenges, opportunities, and evolving perspectives surrounding battery manufacturing scrap recycling. In conclusion, we aim to contribute to the knowledge base of battery manufacturing scrap recycling and promote a more comprehensive understanding of the subject.

25 ENERGY STORAGE↗

DOE OSTI2025

Unusual Li 2 O sublimation promotes single-crystal growth and sintering

Li 2 O is rarely used for cathode material synthesis due to its high melting point (1,438 °C). Here we discover that Li 2 O can sublimate at 800-1,000 °C under ambient pressure, opening new possibilities for cathode synthesis. We propose a mechanism that enables synthesis of single crystals-such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) or LiNi 0.9 Mn 0.05 Co 0.05 O 2 (NMC90)-without direct contact with Li 2 O salts. We show that Li 2 O vapour successfully converts spent polycrystalline NMC811 into segregated single crystals without milling or post-treatment. The Li 2 O vapour, derived from Li 2 O solids, diffuses rapidly and reacts with precursors, mimicking a molten-salt environment, which facilitates single-crystal growth. The chemical lithiation process continuously drives Li 2 O sublimation, sintering the crystals. Single crystals derived from Li 2 O and fresh precursors or spent polycrystals exhibit outstanding cycling after 1,000 cycles in full cells. The demonstrated Li 2 O sublimation and its universal role in promoting single-crystal growth provides an effective approach for single-crystal synthesis, scale-up and recycling.

25 ENERGY STORAGE↗

DOE OSTI2021

Influence of solvent structure and hydrogen bonding on catalysis at solid–liquid interfaces

Solvent molecules interact with reactive species and alter the rates and selectivities of catalytic reactions by orders of magnitude. Specifically, solvent molecules can modify the free energies of liquid phase and surface species via solvation, participating directly as a reactant or co-catalyst, or competitively binding to active sites. These effects carry consequences for reactions relevant for the conversion of renewable or recyclable feedstocks, the development of distributed chemical manufacturing, and the utilization of renewable energy to drive chemical reactions. First, we describe the quantitative impact of these effects on steady-state catalytic turnover rates through a rate expression derived for a generic catalytic reaction (A → B), which illustrates the functional dependence of rates on each category of solvent interaction. Second, we connect these concepts to recent investigations of the effects of solvents on catalysis to show how interactions between solvent and reactant molecules at solid–liquid interfaces influence catalytic reactions. Furthermore, this discussion demonstrates that the design of effective liquid phase catalytic processes benefits from a clear understanding of these intermolecular interactions and their implications for rates and selectivities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Toward sustainable electrochemically mediated separations driven by renewable energy

Environmental pollution, water scarcity, resource shortage, and fossil fuel reliance have all represented threats to a sustainable future. Separation processes play a pivotal role in improving sustainability in fields such as industrial processes, resource recycling, wastewater treatment, and water desalination, among others. Electrochemical systems have gained increased attention as effective separation platforms, not only in performance but also as a potentially energy-efficient approach. However, the reliance on non-renewable energy sources, such as fossil fuels, for electricity generation limits the advancement toward a fully sustainable separation process. Integration of separation processes with eco-friendly renewable energy sources can increase overall sustainability and decrease carbon footprint. Here, in this review, we provide an overview of electrochemical separations and recent efforts to integrate them with renewable energy sources such as heat and solar energy. We discuss electrochemical separations, including electrosorption and electrodialysis, and research to transition these processes to thermoelectrochemical (TEC) and photoelectrochemical (PEC) platforms. Finally, we discuss current challenges and future prospects in direct integration of renewable energy sources with separation processes.

electrochemistry↗

DOE OSTI2024

“Production of High Specific Activity 155 Tb, 161 Tb and 203 Pb for Research and Clinical Applications: Effective Target Design, Target Material Recycling and Radioisotope Separation”

Radioisotopes are essential for the development and application of radiopharmaceuticals that target specific diseases, such as cancer, offering unique potential for precision medicine. The growing demand for theranostic radioisotopes underscores their critical role in personalized medicine, where they enhance diagnostic imaging, minimize patient radiation exposure, and improve targeted tissue uptake, particularly in receptor- and antigen-directed therapies. The theranostic pair terbium-155 (diagnostic) and terbium-161 (therapeutic) holds significant promise for advancing individualized, targeted, and dosimetry-driven radiotherapies. However, the United States currently lacks routine and reliable production of these isotopes. This project made significant progress toward addressing this supply issue by developing production and separation methods for terbium-155 and terbium-161 while also training the next generation of the nuclear and radiochemistry workforce. This grant also strengthened collaboration between scientists at the University of Washington, the University of Missouri and Brookhaven National Laboratory. The research effort focused on evaluating target preparation methods, optimizing irradiation parameters, and refining isolation processes. In addition, the project provided extensive hands-on training to graduate students and postdoctoral fellows, equipping them with expertise in radioisotope production technologies and fostering the growth of the nuclear science workforce.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2025

Conjugate Heat Transfer Modeling of Salt-Filled Fuel Pins for Stable Salt Reactor Safety Analysis

The Stable Salt Reactor (SSR) combines the proven structural design of light water reactor fuel assemblies with the inherent safety and fuel-cycle advantages of molten salt technology. In its fast reactor configuration, the SSR utilizes recycled nuclear waste as fuel, sealed within narrow salt-filled fuel pins and cooled by a surrounding liquid salt coolant. Reliable transfer of heat from the molten fuel salt through the cladding to the external coolant is essential for both reactor safety and performance. This work investigates conjugate heat transfer (CHT) in the SSR’s salt-filled fuel pins using NekRS, a high-fidelity spectral element computational fluid dynamics (CFD) solver. The analyses capture internal natural convection within the molten fuel salt and external forced convection in the coolant, under steady-state and transient operating conditions. Parametric studies evaluate how variations in reactor power and coolant flow rate influence heat transfer distributions and system response. The high-fidelity CFD results are time-averaged and post-processed for direct comparison with moderate-fidelity Reynolds-averaged Navier–Stokes (RANS) models, and for the development of reduced-order models within the SAM system code. These validated models support fast-running safety analyses of normal and off-normal transients, improving predictive capability for key safety margins. By integrating advanced CFD with system-level safety tools, this study strengthens the modeling framework for SSR design, reduces uncertainty in molten salt CHT simulations, and accelerates the engineering and licensing of next-generation nuclear reactors.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2021

One of These Things IS Like the Other: Pursuing a New Taxonomy of Industry for Improved Energy System Modeling

Industrial processes drive the exchange of materials, energy, and currency throughout the economy. These processes are powered by electricity and direct combustion, with variation in their operation even within the same industry. This heterogeneity makes it difficult for large models, including the National Energy Modeling System (US), to project their energy use while remaining tractable. Decarbonization and ensuing changes to the energy system require changes to industrial processes while offering opportunities for process innovation, but the extent and nature of changes are difficult to model with current classification schemes and corresponding data. The North American Industrial Classification (NAICS) is an economic taxonomy of industries, but its categories are less meaningful from an energy and material flow perspective. For example, a facility that makes steel from iron ore in a blast furnace/basic oxygen furnace is categorized under the same NAICS code as a facility that makes steel from scrap in an electric arc furnace despite the scale, use of recycled scrap versus iron ore, and energy use differences in the two facility types. Exploratory analysis is performed on a large dataset used for plant-level energy assessment in order to detect clusters that can aid in better modeling of industry for energy analysis in an evolving system with breakthrough technologies.

28 EE - Advanced Manufacturing Office (EE-5A)↗

DOE OSTI2021

Evaluation of Electrodialysis Desalination Performance of Novel Bioinspired and Conventional Ion Exchange Membranes with Sodium Chloride Feed Solutions

Electrodialysis (ED) desalination performance of different conventional and laboratory-scale ion exchange membranes (IEMs) has been evaluated by many researchers, but most of these studies used their own sets of experimental parameters such as feed solution compositions and concentrations, superficial velocities of the process streams (diluate, concentrate, and electrode rinse), applied electrical voltages, and types of IEMs. Thus, direct comparison of ED desalination performance of different IEMs is virtually impossible. While the use of different conventional IEMs in ED has been reported, the use of bioinspired ion exchange membrane has not been reported yet. The goal of this study was to evaluate the ED desalination performance differences between novel laboratory‑scale bioinspired IEM and conventional IEMs by determining (i) limiting current density, (ii) current density, (iii) current efficiency, (iv) salinity reduction in diluate stream, (v) normalized specific energy consumption, and (vi) water flux by osmosis as a function of (a) initial concentration of NaCl feed solution (diluate and concentrate streams), (b) superficial velocity of feed solution, and (c) applied stack voltage per cell-pair of membranes. A laboratory‑scale single stage batch-recycle electrodialysis experimental apparatus was assembled with five cell‑pairs of IEMs with an active cross-sectional area of 7.84 cm2. In this study, seven combinations of IEMs (commercial and laboratory-made) were compared: (i) Neosepta AMX/CMX, (ii) PCA PCSA/PCSK, (iii) Fujifilm Type 1 AEM/CEM, (iv) SUEZ AR204SZRA/CR67HMR, (v) Ralex AMH-PES/CMH-PES, (vi) Neosepta AMX/Bare Polycarbonate membrane (Polycarb), and (vii) Neosepta AMX/Sandia novel bioinspired cation exchange membrane (SandiaCEM). ED desalination performance with the Sandia novel bioinspired cation exchange membrane (SandiaCEM) was found to be competitive with commercial Neosepta CMX cation exchange membrane.

42 ENGINEERING↗

DOE OSTI2025

Packing density optimization and recyclability of multi-modal SiC powder feedstocks in binder jet additive manufacturing

Achieving high powder packing density is critical in binder jet additive manufacturing (BJAM), as it directly influences the final part density, mechanical properties, and sintering behavior. Multi-modal powder blends, which combine particles of different sizes, have been explored as a strategy to optimize packing efficiency and minimize defects. In this study, bimodal and trimodal powder blends were obtained by mixing silicon carbide powder in three different sizes. These results show that increased powder density is achievable with bimodal powder blends but is reduced in trimodal blends, and it was found that a 13 % increase in the powder tap density was achieved using a bimodal blend of powder. The powder size distribution of the bimodal blend was measured at various stages during binder jet additive manufacturing and, no measurable powder separation occurred even after eight prints. Altogether, this study shows limited advantage to trimodal powder blends but good promise for bimodal blends for increasing printed density while maintaining reusability in the binder jet process.

Aguirre, Trevor G. [Oak Ridge National Laboratory ↗

DOE OSTI2023

Dioctyl ether radiolysis under used nuclear fuel reprocessing conditions: Foundational knowledge for the development of sacrificial ligand grafts

Radiation-induced ligand destruction and concomitant degradation product formation is unavoidable under envisioned used nuclear fuel reprocessing conditions, and ultimately limits the recyclability of a given solvent system formulation. With this in mind, a novel approach to ligand innovation for advanced separations processes is in the design of tailored “protomolecules,” which when exposed to ionizing radiation undergo desired chemical transformations, thereby allowing for a reprocessing solvent system to advantageously evolve with absorbed radiation dose. Here we provide foundational knowledge for the time-resolved (electron pulse) and steady-state (cobalt-60 gamma) radiolytic behavior of dioctyl ether, a protomolecule grafting surrogate. Gamma irradiation of single-phase solutions of dioctyl ether (5–100 vol.%) in n-dodecane resulted in the loss of dioctyl ether (G = -0.72 µmol J –1 ) and the formation of octane (G = 0.11 µmol J –1 ) and octanol (G = 0.15 µmol J –1 ) degradation products, the latter of which is a known reprocessing phase modifier and radioprotectant. Further, these radiation-induced changes were attributed to direct radiation effects, for more concentrated dioctyl ether solutions, and indirect radiation effects, predominantly driven by the reaction of dioctyl ether with the dodecane radical cation, for which we report a second-order rate coefficient of k = (1.53 ± 0.05) × 10 10 L mol –1 s –1 . Under typical biphasic extraction (4.0 mol L –1 HNO 3 ) and strip (0.1 mol L –1 HNO 3 ) reprocessing conditions, gamma irradiation of 5 vol.% dioctyl ether solvent systems afforded negligible change in the rate of parent molecule destruction but promoted significant differences in the radiolytic behavior of its degradation products. These differences are attributed to their respective interactions with [dioctyl ether/HNO 3 /H 2 O] and [octanol/HNO 3 /H 2 O] adducts extracted into the organic phase. Overall, these results support the grafting of ether linkages to advanced separations ligands (e.g., modified diglycolamides).

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2022

Direct synthesis of branched hydrocarbons from CO 2 over composite catalysts in a single reactor

The thermocatalytic hydrogenation of CO 2 to hydrocarbons using a composite catalyst system in a single reactor under mild reaction conditions was investigated, by combining methanol synthesis, methanol dehydration and dimethyl ether homologation catalysts. High selectivity to isoparaffins, which are versatile precursors to sustainable aviation fuels, was achieved. The use of Cu/BEA significantly improved both the conversion of oxygenates and the hydrocarbon yield compared to HBEA by facilitating H-incorporation in the C-chain growth during the homologation reaction. A study of catalyst composition and reaction conditions revealed that nearly complete conversion of oxygenates was achieved using a stacked-bed configuration, providing high C-selectivity to C 4+ hydrocarbons (34.1% among all products and 95.5% in products excluding CO). The ability to completely convert oxygenates to hydrocarbons and achieve high CO-free selectivity to desired hydrocarbon products is unprecedented in CO 2 -to-hydrocarbon reports, and advantageous for downstream separation, as CO can be easily separated and recycled to improve overall hydrocarbon production in an integrated process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Dehalogenation reactions between halide salts and phosphate compounds

Reactions between phosphoric acid [H 3 PO 4 ] or ammonium hydrogen phosphates [i.e., NH 4 H 2 PO 4 , (NH 4 ) 2 HPO 4 ] and halide salts can be used to dehalogenate (remove halides from) salt-based waste streams, where the process of removing halides yields products that have more efficient disposal pathways for repository storage. In this context, the term efficiency is defined as higher waste loadings and simplified immobilization processes with potential for recycle of certain salt components (e.g., 37 Cl as H 37 Cl or NH 4 37 Cl). The main streams identified for these processes are nuclear wastes generated during electrochemical reprocessing of used nuclear fuel as well as used halide salts from molten salt reactor operation. The potential byproducts of these reactions are fairly consistent across the range of halide species (i.e., F, Cl, Br, I) where the most common are hydrogen halides [e.g., HCl (g) ] or ammonium halides (e.g., NH 4 Cl). However, trihalide compounds (e.g., NCl 3 ), nitrogen triiodide ammine adducts [NI 3 ·(NH 3 ) x ], and ammonium triiodide (NH 4 I 3 ) are also possible. Several of these byproducts (i.e., NCl 3 , NBr 3 , NI 3 , and NH 4 I 3 ) are shock-sensitive contact explosives so their production in these processes must be tracked and carefully controlled, which includes methods of immediate neutralization upon production such as direct transport to a caustic scrubber for dissolution. Several benefits arise from utilizing H 3 PO 4 as the phosphate additive during dehalogenation reactions for making iron phosphate waste forms including more oxidized iron (higher Fe 3+ :Fe 2+ ratios), higher chemical durabilities, and the avoidance of trihalides, but the byproducts are hydrogen halides, which are corrosive and require special handling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Bending and shear improvements in 3D-printed core sandwich composites through modification of resin uptake in the skin/core interphase region

Fused deposition modeling (FDM) printed polymers are rarely used as a structural material due to anisotropic and low mechanical properties compared with conventional composites. In recent years, greater need has been expressed for recycling of materials, such as recyclable FDM, at the end of service life to reduce environmental pollution and manufacture cost. However, how the amount of resin uptake in the skin and skin/core interphase affects the bending and shear performance of the sandwich composites when replacing the low strength and ductile core (conventional core) with a high strength and brittle core (FDM printed PLA (polylactic acid) core) still remains unclear. A new manufacturing routine is needed to improve the incorporation of FDM printed polymers in composite structures. In this work, FDM printed PLA was used as core material and sandwiched between two unidirectional glass fiber reinforced polymer (GFRP) skins to form a sandwich composite by compression-molding (CM) process, which provides a good manufacturing strategy for skin/core interphase modification. The significance of the CM process is proved by investigating the effect of resin uptake on bending and in-plane/out-of-plane shear performances. Current first order shear deformation (FSDT) theory lacks a direct connection between the in-plane shear stress and out-of-shear stress in the core region of sandwich composites. With the help of DIC, a connection between the in-plane shear and the out-of-plane shear strain was built and in-plane shear properties can acquire through out-of-plane shear properties, hence reducing the redundancy of sample preparation or the need for simulation. A significant improvement was found compared with the optimized resin uptake (Optimized resin uptake range: 20.43%–22.86 wt%) 3D-printed PLA core sandwich composite and lowest performance sandwich composite (Improvement: in-plane shear strength (~34%)/modulus (~29%), out-of-plane shear strength (~25%)/modulus (~31%), specific peak bending load (~19%)). Finally, compared with balsa core sandwich composites, the 3D-printed cores are suitable for use in composite sandwich structures in many applications with a satisfactory strength-to-weight ratio.

3D-printed core sandwich composite↗

DOE OSTI2025

Recyclable Design for Retaining High Solar Absorptivity of the Media in CSP

Efficient thermal energy storage is pivotal to lowering the levelized cost of electricity (LCOE) for Concentrating Solar Power (CSP) plants. In solid-particle systems, however, prolonged high-temperature service degrades particle solar absorptivity, eroding overall efficiency. This project demonstrates a hydrogen-assisted recovery process that reliably restores absorptivity to >90 %, offering a practical route to sustain long-term CSP performance. Bench-scale investigations mapped the reduction kinetics of optically faded particles across hydrogen concentrations, temperatures, and residence times. Coupling mass-spectrometric monitoring with machine-learning optimization minimized energy demand while maximizing absorptivity gain. The resulting process window—moderate hydrogen partial pressures, 15–30 min dwell times, and temperatures well below initial calcination levels—cuts energy consumption well below that of incumbent re-blackening methods. A prototype recovery reactor processed multiple 2 kg batches with repeatable outcomes, confirming scalability and operational robustness. Integrated techno-economic analysis indicates material and operating cost reductions exceeding 15 % relative to conventional particle replacement or chemical re-coating, translating directly into lower LCOE for next-generation CSP facilities. By uniting fundamental reaction-kinetics insight with pragmatic engineering, this work advances the solid-particle pathway, delivering a cost-effective, field-deployable solution to one of CSP’s key durability challenges and strengthening the commercial outlook for high-temperature renewable power.

14 SOLAR ENERGY↗

DOE OSTI2023

Sustainable production of plastic degrading enzymes

The 21st century faces the challenge of transitioning to a climate-neutral economy. This hurdle will need to be addressed in a myriad of approaches, including all societal spheres, as highlighted in several UN and EU reports, including new and accessed technologies. Among them, biotechnology can play a core role by exploiting its environmental benefits (e.g., substituting fossil-based products and expected greenhouse emission reductions). In some cases, biotech can even outperform fossil counterparts' features (e.g., the biodegradability of some bioplastics). Microalga is an attractive bioplastic feedstock in this scenario since it directly substitutes petroleum and captures CO2. However, albeit its environmental benefits, the microalgal process still needs to be tipped economically and the net-positive ecological impact improved to drive adoption. To that end, we envisioned the use of a green alga as a source of bioplastic feedstock and industrial enzymes, combining natural traits of microalgae with engineered properties in a resourceful process to petroleum-based products replacement. As proof of concept, we demonstrated that we could use C. reinhardtii, a green algae, to produce plastic-degrading enzymes. We assemble a vector to secrete PHL7, a recently described PETase, capable of degrading post-consumer PET plastic. We successfully engineered the cell line to secrete the plastic-degrading enzyme. We confirmed the secretion of the enzyme by observing halos in agar plates supplemented with plastic dispersions, enzymatic assays, zymograms, and protein sequencing of supernatant samples. This approach allows using green algae to replace petrochemical-derived plastic while producing the tool necessary to recycle existing plastics sustainably.

Dutra Molino, Joao Vitor↗