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

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A Bifunctional Ionic Liquid for Capture and Electrochemical Conversion of CO 2 to CO over Silver

Electrochemical conversion of CO 2 requires selective catalysts and high solubility of CO 2 in the electrolyte to reduce the energy requirement and increase the current efficiency. In this study, the CO 2 reduction reaction (CO 2 RR) over Ag electrodes in acetonitrile-based electrolytes containing 0.1 M [EMIM][2-CNpyr] (1-ethyl-3-methylimidazolium 2-cyanopyrolide), a reactive ionic liquid (IL), is shown to selectively (>94%) convert CO 2 to CO with a stable current density (6 mA·cm –2 ) for at least 12 h. The linear sweep voltammetry experiments show the onset potential of CO 2 reduction in acetonitrile shifts positively by 240 mV when [EMIM][2-CNpyr] is added. This is attributed to the pre-activation of CO 2 through the carboxylate formation via the carbene intermediate of the [EMIM] + cation and the carbamate formation via binding to the nucleophilic [2-CNpyr] – anion. The analysis of the electrode–electrolyte interface by surface-enhanced Raman spectroscopy (SERS) confirms the catalytic role of the functionalized IL where the accumulation of the IL-CO 2 adduct between –1.7 and –2.3 V vs Ag/Ag + and the simultaneous CO formation are captured. Furthermore, this study reveals the electrode surface species and the role of the functionalized ions in lowering the energy requirement of CO 2 RR for the design of multifunctional electrolytes for the integrated capture and conversion.

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

Tailoring electron transfer pathway for photocatalytic N 2 -to-NH 3 reduction in a CdS quantum dots-nitrogenase system

The combination of abiotic photosensitizers with purified enzymes in a biohybrid system offers a promising pathway to utilizing light to accomplish challenging chemical transformations and provides insights into the rational photocatalytic system design for efficient solar-to-chemical energy conversion. In this work, we demonstrate a hybrid photocatalytic system for ammonia production from N2 by combining cadmium sulfide quantum dots (CdS QDs) and Mo-nitrogenase from Azotobacter vinelandii, composed of the iron protein (FeP) and the molybdenum-iron protein (MoFeP). Photoexcited electrons from the CdS QD are delivered by an electron transfer mediator through the FeP to the catalytic MoFeP. The complete system was optimized for the ligand on the CdS QDs, mediators, and reaction conditions. The best results were achieved with β-mercaptoethanol as a QD ligand. The mediator test revealed that 1,1'-bis(3-sulfonatopropyl)-4,4'-bipyridinium (SPr)2V (-0.4 V vs. NHE) supports the reduction of protons and N 2 to H 2 and ammonia catalyzed by nitrogenase. However, in the presence of 1,1'-trimethylene-2,2'-bipyridinium TQ (-0.54 V vs. NHE) as a mediator, nitrogenase catalysis resulted in remarkably more products. The UV-vis and in situ potentiometric studies revealed that better performance with TQ is achieved due to the significantly more negative solution potential allowing for efficient reduction of FeP. As a result, the quantum yield for conversion of absorbed photons to ammonia attains 16%, far exceeding that of previously reported nitrogenase-based systems. This work reveals the importance of tuning the electron transfer pathways in photocatalytic systems and illustrates a potent strategy for efficient electronic coupling of a photosensitizer and an N 2 reduction catalyst.

36 MATERIALS SCIENCE↗
DOE OSTI2020

2‐Aminobenzenethiol‐Functionalized Silver‐Decorated Nanoporous Silicon Photoelectrodes for Selective CO 2 Reduction

Abstract A molecularly thin layer of 2‐aminobenzenethiol (2‐ABT) was adsorbed onto nanoporous p‐type silicon (b‐Si) photocathodes decorated with Ag nanoparticles (Ag NPs). The addition of 2‐ABT alters the balance of the CO 2 reduction and hydrogen evolution reactions, resulting in more selective and efficient reduction of CO 2 to CO. The 2‐ABT adsorbate layer was characterized by Fourier transform infrared (FTIR) spectroscopy and modeled by density functional theory calculations. Ex situ X‐ray photoelectron spectroscopy (XPS) of the 2‐ABT modified electrodes suggests that surface Ag atoms are in the +1 oxidation state and coordinated to 2‐ABT via Ag−S bonds. Under visible light illumination, the onset potential for CO 2 reduction was −50 mV vs. RHE, an anodic shift of about 150 mV relative to a sample without 2‐ABT. The adsorption of 2‐ABT lowers the overpotentials for both CO 2 reduction and hydrogen evolution. A comparison of electrodes functionalized with different aromatic thiols and amines suggests that the primary role of the thiol group in 2‐ABT is to anchor the NH 2 group near the Ag surface, where it serves to bind CO 2 and also to assist in proton transfer.

Kan, Miao↗
DOE OSTI2021

Spontaneous N 2 formation by a diruthenium complex enables electrocatalytic and aerobic oxidation of ammonia

The electrochemical conversion of ammonia to dinitrogen in a direct ammonia fuel cell (DAFC) is a necessary technology for the realization of a Nitrogen Economy. Previous efforts to catalyze this reaction with molecular complexes require the addition of exogenous oxidizing reagents or application of potentials greater than the thermodynamic potential for the oxygen reduction reaction (ORR) – the cathodic process of a DAFC. We report a stable metal–metal bonded diruthenium complex that spontaneously produces dinitrogen from ammonia under ambient conditions. The resulting reduced diruthenium material can be re-oxidized with oxygen for subsequent reactions with ammonia, demonstrating its ability to spontaneously promote both half reactions necessary for a DAFC. Here, the diruthenium complex also acts as a redox mediator for the electrocatalytic oxidation of ammonia to dinitrogen at potentials as low as –255 mV vs Fc 0/+ and operates below the ORR potential in alkaline conditions, thus achieving a thermodynamic viability relevant for the future development of DAFCs.

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

Transformational Sorbent-Based Process for a Substantial Reduction in the Cost of CO 2 Capture

InnoSepra’s project, “Transformational Sorbent-Based Process for a Substantial Reduction in the Cost of CO 2 Capture,” utilized computational tools, materials characterization, and lab and pilot-scale testing to optimize previously identified materials to determine their performance under post-combustion capture conditions. InnoSepra utilized the test results to determine the energy required for regeneration and to develop a process design/analysis to demonstrate the application of developed materials for post-combustion capture. A techno-economic analysis was performed to fully assess the potential of the materials for post-combustion capture. InnoSepra also updated the State Point Data Table and completed the environmental, health, and safety (EH&S) Risk Assessment. The InnoSepra CO 2 capture technology has the potential for a significant reduction in the CO 2 capture cost for the power plant and industrial flue gases.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

Global warming potential estimates of mass timber constructions beyond the first life: A dynamic radiative forcing modeling approach

In the face of a warming planet, steps must be taken to reduce the greenhouse gas emissions (GHG) associated with our building industry, which is a significant contributor to global emissions. Large, prefabricated wood elements such as mass timber panels (MTP) have great potential to achieve these reductions as they help displace high-embodied‑carbon materials like concrete and steel. Furthermore, storing the wood's biogenic carbon in buildings benefits the climate because it delays the eventual release of the carbon into the atmosphere. While these climate impacts have been assessed for the construction phase of mass timber buildings, relatively few life cycle assessment (LCA) studies have evaluated the climate impacts for the buildings' end-of-life (EOL) phase. This research estimates the climate impacts of four EOL scenarios for MTP: reusing as MTP, recycling into particleboard, incinerating, and landfilling. Using dynamic radiative forcing modeling and factoring in temporal GHG emissions and biogenic carbon storage, the global warming potential impacts are calculated for construction, deconstruction, and EOL processing of hybrid mass timber buildings in the U.S. Pacific Northwest for 160 years (GWP 160 ). The 160-year temporal scale used in this paper is an arbitrary scale, with the first 80 years being the assumed life of the building, followed by a series of reuse, recycle, or disposal scenarios over the second 80 years of that temporal scale. Of the four EOL scenarios considered in this paper, the ‘reuse’ scenario has the lowest net GWP 160 impact (calculated by summing the GWP 160 and carbon storage benefits, i.e., GWP$^{bioCS}_{160}$ ), emerging as a climate-preferred scenario, followed by ‘landfill’, ‘incinerate’, and ‘recycle’ scenarios. The lower net GWP 160 impact associated with the reuse scenario is due to the low fossil carbon emissions during EOL processing, as well as the biogenic carbon storage benefits. The results of this study also highlight the importance of efficient reuse and recycling strategies for wood in MTP.

42 ENGINEERING↗
DOE OSTI2023

The Genetics of Aerotolerant Growth in Zymomonas mobilis

Reduced genome bacteria are genetically simplified systems that facilitate biological study and industrial use. The free-living Alphaproteobacterium, Zymomonas mobilis, has a naturally reduced genome containing fewer than 2000 protein coding genes. Despite its small genome, Z. mobilis thrives in diverse conditions including the presence or absence of atmospheric oxygen. However, insufficient characterization of essential and conditionally essential genes has limited broader adoption of Z. mobilis as a model Alphaproteobacterium. Here, we use genome-scale CRISPRi-seq to systematically identify and characterize Z. mobilis genes that are conditionally essential for aerotolerant or anaerobic growth, or are generally essential across both conditions. Comparative genomics revealed that the essentiality of most "generally essential" genes was shared between Z. mobilis and other Alphaproteobacteria, validating Z. mobilis as reduced genome model. Among conditionally essential genes, we found that the DNA repair gene, recJ, was critical only for aerobic growth but reduced the mutation rate under both conditions. Further, we show that genes encoding the F1FO ATP synthase and Rnf respiratory complex are required for anaerobic growth of Z. mobilis. Combining CRISPRi partial knockdowns with metabolomics and membrane potential measurements, we determined that the ATP synthase generates membrane potential that is consumed by Rnf to power downstream processes. Rnf knockdown strains accumulated isoprenoid biosynthesis intermediates, suggesting a key role for Rnf in powering essential biosynthetic reactions. Our work establishes Z. mobilis as a streamlined model for alphaproteobacterial genetics, has broad implications in bacterial energy coupling, and informs Z. mobilis genome manipulation for optimized production of valuable isoprenoid-based bioproducts

Alphaproteobacteria↗
DOE OSTI2026

Hydrogen applications in airport operations: a review using the Port Authority of New York and New Jersey as an illustrative airport system

Airports combine aircraft propulsion, ground operations, stationary power systems, and fuel logistics in ways that make emissions reduction technically and operationally complex. Existing studies often assess hydrogen applications in these areas separately, limiting understanding of the shared infrastructure, safety, and operational constraints that shape airport deployment. This review evaluates hydrogen across three airport-relevant operational domains: aviation propulsion, ground support equipment and vehicles, and stationary power systems. Within aviation propulsion, the review examines sustainable aviation fuel production and hydrogen-powered aircraft as two distinct hydrogen-relevant pathways. The Port Authority of New York and New Jersey is used as an illustrative airport system to relate the literature to a real operating context. Drawing on peer-reviewed studies, technical reports, demonstration projects, and public operational information, the review also includes screening-level calculations of hydrogen demand and potential CO 2 e reductions for selected applications. The findings show that hydrogen's role is highly application-specific. Near-term opportunities are strongest where hydrogen serves as a low-carbon process input, supports selected high-utilization ground equipment, or contributes to resilient stationary power-system configurations. Hydrogen-powered aircraft remain a longer-term option because storage, fueling infrastructure, certification, cost, and NO x management continue to constrain deployment. Across all domains, infrastructure readiness, fuel logistics, safety requirements, and leakage management emerge as recurring determinants of viability. Future research should focus on cross-domain infrastructure planning, comparative assessment of hydrogen against alternative pathways, improved treatment of leakage and non-CO 2 effects, and clearer safety and regulatory frameworks for airport deployment.

08 HYDROGEN↗
DOE OSTI2025

Isolation of Inner-Sphere Aquo Complexes of Samarium(II)

The cis-anti-cis and cis-syn-cis isomers of [Sm(dicyclohexano-18-crown-6)(H 2 O) 2 ]I 2 exhibiting trans water molecules bound to the Sm 2+ ion have been isolated and characterized. Sm 2+ possesses an electrochemical potential sufficient for water reduction, and thus these complexes add to the recent body of evidence that the oxidation of Sm 2+ by water can operate by a mechanism that is not straightforward. These complexes are obtained by the direct addition of stoichiometric amounts of water to solutions of the respective Sm(dicyclohexano-18-crown-6)I 2 isomers under an inert atmosphere. The parent complex, Sm(dicyclohexano-18-crown-6)I 2 , lacking coordinating water molecules can be obtained through rigorous exclusion of water. It was determined that the bulky cyclohexano-substituents deter intramolecular interactions between [Sm(dicyclohexano-18-crown-6)(H 2 O) 2 ]I 2 complexes and slow the oxidization of the metal centers. The extent of the stability of these complexes to the presence of water has been further probed through cyclic voltammetry, where it was found that the redox potential of both isomers of [Sm(dicyclohexano-18-crown-6)(H 2 O) 2 ]I 2 maintains quasi-reversible behavior with a 50,000-fold excess of water to Sm 2+ in solution with the cis-syn-cis complex being quasi-reversible at even higher concentrations of water. Solution-phase spectroscopy of these complexes in acetonitrile shows a corresponding hypsochromic shift of the Sm 2+ 4f → 5d transition typically observed in the visible region from Sm 2+ complexes. Here, the crystalline compounds obtained in this study support solid-state spectroscopic trends observed from other Sm 2+ crown-ether complexes containing iodide counterions, wherein the proximity of the iodide ions to the metal center determines whether the complex can exhibit 4f → 4f photoluminescence.

Crystals↗
DOE OSTI2020

Microalgae Biomass Production for Utilization of CO2 and Mitigation of Greenhouse Gas Emissions

Microalgal cultivation processes for production of foods, feeds, fuels, fertilizers and other bioproducts and wastewater treatment are being considered for reducing CO2 and other greenhouse gas emissions. Major differences between microalgae and higher plant biomass cultivation are include their potential for much higher productivities, their higher content of major (N-P-K) and minor nutrients, and the challenge of harvesting such microscopic plants. Most critical, microalgal mass cultures, unlike higher plants, currently require fertilization with concentrated sources of CO2. As practically all of the C fixed into algal biomass will be re-emitted into the atmosphere in short order, algae processes do not sequester carbon. Their potential for CO2 emissions reductions must thus be based on comparisons with current technologies for the production of competing products, such as biofuels or animal feeds, or in wastewater treatment. Further, due to economic limitations to flue gas transport (3 to 12 % CO2), as well as highly variable diurnal and seasonal CO2 utilization and limited land and water availability near most CO2 sources, only a small fraction of waste CO2 emissions will be directly utilizeable for microalgae biomass production. However, for long-distance transport, flue gas CO2 capture by chemical processes would greatly increase the costs of flue gas utilization. More concentrated, sources of CO2 from refineries, fertilizer, chemical plants, and fermentations are available, but are also very limited relative to the quantities required for commodity production. Microalgae can also be cultivated on organic wastes, which provide both nutrients (N, P, K, etc.) and organic and inorganic carbon for algal growth, reducing greenhouse gas emissions compared to conventional treatment processes. To maximize the potential for algae biomass production and CO2 utilization, direct capture of CO2 from air will be required. This could be accomplished with the algal cultivation process itself in large open-raceway ponds, through chemical and biological enhancements of CO2 transfer into algal cutures. The relative productivities, economics, greenhouse gas balances, and resource potentials of these alternative CO2 sources for large-scale production of microalgae will be reviewed.

09 BIOMASS FUELS↗
DOE OSTI2023

The genetics of aerotolerant growth in an alphaproteobacterium with a naturally reduced genome

Reduced genome bacteria are genetically simplified systems that facilitate biological study and industrial use. The free-living alphaproteobacterium Zymomonas mobilis has a naturally reduced genome containing fewer than 2,000 protein-coding genes. Despite its small genome, Z. mobilis thrives in diverse conditions including the presence or absence of atmospheric oxygen. However, insufficient characterization of essential and conditionally essential genes has limited broader adoption of Z. mobilis as a model alphaproteobacterium. Here, we use genome-scale CRISPRi-seq (clustered regularly interspaced short palindromic repeats interference sequencing) to systematically identify and characterize Z. mobilis genes that are conditionally essential for aerotolerant or anaerobic growth or are generally essential across both conditions. Comparative genomics revealed that the essentiality of most “generally essential” genes was shared between Z. mobilis and other Alphaproteobacteria, validating Z. mobilis as a reduced genome model. Among conditionally essential genes, we found that the DNA repair gene, recJ, was critical only for aerobic growth but reduced the mutation rate under both conditions. Further, we show that genes encoding the F1FO ATP synthase and Rhodobacter nitrogen fixation (Rnf) respiratory complex are required for the anaerobic growth of Z. mobilis. Combining CRISPRi partial knockdowns with metabolomics and membrane potential measurements, we determined that the ATP synthase generates membrane potential that is consumed by Rnf to power downstream processes. Rnf knockdown strains accumulated isoprenoid biosynthesis intermediates, suggesting a key role for Rnf in powering essential biosynthetic reactions. Our work establishes Z. mobilis as a streamlined model for alphaproteobacterial genetics, has broad implications in bacterial energy coupling, and informs Z. mobilis genome manipulation for optimized production of valuable isoprenoid-based bioproducts.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Water Interplays during Dysprosium Electrodeposition in Pyrrolidinium Ionic Liquid: Deconvoluting the Pros and Cons for Rare Earth Metallization

The electrochemical production of rare earth metals (REMs) in ionic liquids (ILs) has received much attention as a promising, sustainable and replacement to the molten salt electrolysis. Water additives have been recently suggested as a strategy to overcome the limitations of the ionic liquid process, but without complete assessment of its overall viability for the REMs production. In this regard, a full investigation of water impact on dysprosium (Dy) electrodeposition in pyrrolidinium triflate (BMPyOTf) ionic liquid was carried out. Water introduction was revealed to involve an interplay of implications on the electrodeposition process, including coordination, speciation, reduction pathways, interfacial dynamics, nucleation and metal stability and purity. In highly dry conditions, the reduction occurs at very negative potentials (-3.3V) in a consecutive pathway, resulting in negligible metal electrodeposition (low rate and efficiency) at the electrode surface. Initial water introduction (<30% molar fraction) leads to partitioning of the Dy complex between water and IL coordinated speciation, giving rise to an additional wave at more positive potentials (-2.4V). Probing and quantification of the heterogeneous Dy speciation by spectroscopic analyses enabled the uncovering of the reduction mechanism and accurate evaluation of the mass transport properties. While lowering the reduction thermodynamics, water addition also improved the nucleation, deposition rate and faradaic efficiency. In spite of these benefits, stripping voltammetric analysis also indicated substantial chemical reactivity of the deposited Dy metal with water additives and/or electrolyte components, under extended timescales. Surface characterization of the obtained product confirmed limited Dy metal stability (mostly oxidized/fluorinated) and purity (~60%) in the studied system. Moreover, high water introduction (>30% molar fraction) was shown to trigger a fast hydrogen evolution reaction (HER), downgrading the robustness of system efficiency. We report the overall impact of water additives seems to engender both promoting and mitigating effects on the Dy electrodeposition process, making the case for more innovative strategies to be sought.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Hierarchically Porous Multimetal‐Based Carbon Nanorod Hybrid as an Efficient Oxygen Catalyst for Rechargeable Zinc–Air Batteries

Abstract The lack of efficient strategies to address the intrinsic activity, site accessibility, and structural stability issues of metal‐carbon hybrid catalysts is restricting their real‐world implementation on the basis of rechargeable zinc–air batteries. Herein, a dual metal–organic frameworks (MOFs) pyrolysis strategy is developed to regulate the intrinsic activity and porous structure of the derived catalysts, where a Fe 2 Ni_MIL‐88@ZnCo_zeolitic imidazolate framework (ZIF), with a hierarchically porous structure, multifunctional components, and an integrated architecture, acts as an ideal precursor to obtain multimetal based porous nanorod (FeNiCo@NC‐P). Benefitting from the synergetic effect of the multimetal components, facilitated reactant accessibility, and the well‐retained integrated structure, the resultant FeNiCo@NC‐P catalyst exhibits an oxygen reduction reaction half‐wave potential of 0.84 V as well as an oxygen evolution reaction potential of 1.54 V at 10 mA cm –2 . Furthermore, the practical application of FeNiCo@NC‐P in the zinc–air battery displays a low voltage gap and long‐term durability (over 130 h at a current density of 10 mA cm –2 ), which outperforms the commercial noble metal benchmarks. This work not only affords a competitive bifunctional oxygen electrocatalyst for zinc–air batteries but also paves a new way to design and fabricate MOF‐derived materials with tunable catalytic properties.

Ren, Dezhang↗
DOE OSTI2020

Dual-atom Ag 2 /graphene catalyst for efficient electroreduction of CO 2 to CO

Electrochemical reduction of CO 2 into value-added carbon compounds offers a promising strategy to mitigate global warming, but present challenges for chemistry due to the poor selectivity and stability of electrocatalysts. In this work, we report a dual-atom Ag 2 /graphene catalyst featuring well-defined AgN 3 -AgN 3 active site for CO 2 electrochemical reduction. This dual-atom catalyst can drive CO 2 reduction reaction at a potential as high as -0.25 V, and exhibit excellent CO Faradic efficiency up to 93.4 % with a current density of 11.87 mA cm -2 at -0.7 V and long-term stability, far surpassing the single-atom Ag 1 /graphene and the traditional silver nanoparticle catalysts. Finally, DFT calculations reveal that the dual-atom Ag site lowers the barrier for the formation of *COOH by stabilizing the *CO 2 through the concomitant interactions with the C and an O atom of CO 2 , resulting in excellent catalytic performance.

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

Effect of fuel composition and EGR on spark-ignited engine combustion with LPG fueling: Experimental and numerical investigation

This paper presents an experimental and numerical investigation of a spark-ignited (SI) cooperative fuel research (CFR) engine fueled with different liquefied petroleum gas (LPG) fuels and exhaust gas recirculation (EGR). Here, the effects of LPG fuel composition on engine combustion characteristics are initially evaluated at two different compression ratios (CR). Results show normal combustion at CR 7 and heavy knocking combustion at CR 10 for all the tested fuels, with a more substantial impact for the LPG fuel with high proportions of n-butane species. The Livengood-Wu (LW) integral method is then used to analyze the knock occurrence risk of individual fuel based on the reactivity of the tested fuels. The introduction of EGR then demonstrates the potential of knock intensity reduction below the borderline knock limit. A zonal-based kinetic interactions study is also performed to understand the knock mitigation effectiveness of EGR over the pressure–temperature domain relevant to SI engine operation. Finally, a multidimensional, computational fluid dynamics (CFD) simulation model is shown to predict the LPG combustion characteristics and presents the evolution of in-cylinder temperature and chemical species to demonstrate the development of end-gas autoignition events without and with EGR.

02 PETROLEUM↗
DOE OSTI2022

Patterns of Initial Relapse from a Phase 3 Study of Response-Based Therapy for High-Risk Hodgkin Lymphoma (AHOD0831): A Report from the Children's Oncology Group

The Children's Oncology Group protocol AHOD0831, for pediatric patients with high-risk classical Hodgkin lymphoma (cHL), used response-adapted radiation fields, rather than larger involved-field radiation therapy (IFRT) that were historically used. This retrospective analysis of patterns of relapse among patients enrolled in the study was conducted to study the potential effect of a reduction in RT exposure.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Boron carbide amorphous solid with tunable band gap

Boron carbide B x C (x = 1/6 – 10) powders were synthesized through a microwave-assisted carbothermic reduction reaction as a potential clean energy material. Their crystallographic structures and optical properties were characterized. X-ray diffraction and electron diffraction indicated that the synthesized B x C powders were amorphous. Electron energy-loss spectroscopy demonstrated that the composition of boron and carbon was in amorphous materials, and their chemical bonding were disclosed from Raman scattering spectroscopy. Here, UV-vis absorption spectroscopy indicated that the bandgap of the bulks varied from 2.30 eV to 3.90 eV, tuned by the boron/carbon element ratio.

36 MATERIALS SCIENCE↗