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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

An in situ annealing route to [Bi6O6(OH)2](NO3)4·2H2O/g-C3N4 heterojunction and its visible-light-driven photocatalytic performance

Highlights: • The heterojunction (BBN-g-C{sub 3}N{sub 4}) was synthesized by in situ calcination route. • The baked Bi(NO{sub 3}){sub 3}·5H{sub 2}O as raw material is crucial to obtain highly crystalline BBN-g-C{sub 3}N{sub 4}. • BBN-g-C{sub 3}N{sub 4} exhibited better visible-light-driven photocatalytic activity than Bi{sub 2}O{sub 3}-g-C{sub 3}N{sub 4}. • BBN-g-C{sub 3}N{sub 4} prepared by calcining route possessed better photocatalytic activity than by mechanical mixing method. - Abstract: Known as incomplete hydrolysis products of Bi(NO{sub 3}){sub 3}·5H{sub 2}O, basic bismuth nitrates (BBN), were commonly obtained via a solution route. Herein, BBN-CN ([Bi{sub 6}O{sub 6}(OH){sub 2}](NO{sub 3}){sub 4}·2H{sub 2}O/g-C{sub 3}N{sub 4}) and Bi{sub 2}O{sub 3}-g-C{sub 3}N{sub 4} heterojunctions were prepared in situ by mixing g-C{sub 3}N{sub 4} with baked Bi(NO{sub 3}){sub 3}·5H{sub 2}O and subsequent calcining at 250 °C and 550 °C, respectively. The baked Bi(NO{sub 3}){sub 3}·5H{sub 2}O as a bismuth source was crucial to the formation of highly crystalline BBN, and otherwise, the product was poor-crystalline and low photoactive. The as-prepared BBN-CN exhibited better photocatalytic activity for rhodamine B (RhB) degradation under visible light irradiation than BBN, g-C{sub 3}N{sub 4}, and Bi{sub 2}O{sub 3}-g-C{sub 3}N{sub 4}, although Bi{sub 2}O{sub 3} is more visible-light-active. These could be attributed to higher surface areas and more negative conduction band potentials of BBN, which benefits for capturing the photogenerated electrons to form active O{sub 2}{sup −} radicals. Furthermore, the presence of g-C{sub 3}N{sub 4} plays a crucial role in enlarging visible light response.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Electrochemically-assisted removal of cadmium ions by redox active Cu-based metal-organic framework

An electrochemically-assisted wastewater treatment using Faradaic materials offers a promising technique for the selective removal of hazardous substances. Here, we demonstrate the reversible capture and release of cadmium ions in aqueous solutions, using a redox-active metal-organic framework (MOF) electrode. As-synthesized copper-based MOF (Cu-MOF-74; copper 2,5-dihydroxyterephthalate) is a highly attractive candidate for Faradaic electrosorption due to its large surface area, water stability, and redox-active metal nodes. Our work demonstrates the reversible capture and release of Cd 2+ ions assisted by the electrochemical redox reaction of Cu 2+ /Cu + within the MOF structure. Combined material characterization and electrosorption tests were carried out to determine the operational conditions for maximizing adsorption capacity, energy efficiency, and material stability, thus leading to excellent electrosorption (>100 mg g -1 ) and regeneration efficiency (>90%). This study demonstrates the feasibility of leveraging MOFs containing redox-active metal nodes for the selective separation of toxic cations, and paves the way for promising future applications of these 3-D porous structures for wastewater treatment and environmental remediation.

42 ENGINEERING↗
DOE OSTI2024

Insights into activators on biomass-derived carbon-based composites for electrochemical energy storage

Biomass-derived carbon materials are now an essential source of carbon electrodes for high-performance supercapacitors due to their cost-effectiveness and abundant heteroatom self-doping properties. When preparing porous carbon materials from biomass for supercapacitor use, the use of activators can significantly increase the specific surface area of carbon materials, enhance pore structures, introduce more heteroatoms, promote the generation of various functional groups, and play a crucial role in the capacitance performance of biomass-derived carbon materials. However, the role of activators during the activation process has been overlooked in previous work focused on improving supercapacitor capacitance performance. In addition, there is a lack of comprehensive reviews summarizing the role of activators. Therefore, this work classifies the types of activators, discusses their activation mechanisms, operability, economy, and environmental friendliness, and proposes future development directions for activators. The main mixing methods of activators and carbon materials are also demonstrated, highlighting the advantages and disadvantages of each method. In conclusion, this work could provide valuable insights for the development of activators for high-performance supercapacitors.

25 ENERGY STORAGE↗
DOE OSTI2022

Binder-Free Wood Converted Carbon for Enhanced Water Desalination Performance

Here, the design and synthesis of high-performance and economical carbon electrodes play a critical role in developing energy-efficient water desalination technologies. As a sustainable approach, low-cost and abundant biomass materials are promising candidates to prepare porous carbon for capacitive deionization. In this study, binder-free porous carbon sheets are successfully prepared using natural balsa, pine, and basswood by thermal carbonization and treated by chemical activation. The carbon electrode materials converted from balsa and pine exhibit a comparable salt adsorption performance by capacitive deionization due to the extensive surface area, substantial electrical property, and superior hydrophilic performance. The following activation treatment of the balsa-converted carbon further enhances the surface and electrical properties and benefits the desalination performance. The salt adsorption capacity of the activated balsa electrode exhibits 12.45 mg g -1 . Additionally, 19.52 mg g -1 Pb 2+ and 20.06 mg g -1 Cr 3+ heavy metal adsorption capacity is also observed with the activated balsa electrode in 100 mg L -1 PbCl 2 and 50 mg L -1 CrCl 3 , respectively. To the best of authors’ knowledge, this is the highest NaCl adsorption capacity performance reported thus far by using pure wood converted carbon as the electrode, and these promising results indicate that activated balsa is an extraordinary material for water desalination.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Mo-N-co-doped mesoporous TiO{sub 2} microspheres with enhanced visible light photocatalytic activity

Highlights: • The Mo-N-co-doped mesoporous TiO{sub 2} microspheres were synthesized via a solvothermal method and further nitriding treatment. • The properties of TiO{sub 2} microspheres can be tuned by Mo-N-co-doping. • Photocatalytic rate is much higher than Pure TiO{sub 2} catalyst powder and Mo doped TiO{sub 2} microspheres. • The higher activity is attributed to the large BET surface area, narrow band gap and intense light absorbance in visible region. - Abstract: Mo-N-co-doped mesoporous TiO{sub 2} microspheres were synthesized via a solvothermal method, followed by nitriding treatment under ammonia gas flow. The efficiency of the samples was investigated by monitoring the degradation of Rhodamine-B under visible light irradiation. The experimental results revealed that Mo-N-co-doped mesoporous TiO{sub 2} microspheres showed better performances than Mo-TiO{sub 2} microspheres. It was observed that; 0.1% molar quantity of Mo doped on TiO{sub 2} at 500 °C for 2 h under nitriding conditions gave highest photocatalytic activities. The nitridation under ammonia gas of Mo-TiO{sub 2} samples created oxygen vacant sites and led to incorporation of substitutional and interstitial Nitrogen. The enhanced visible light photocatalytic activities of Mo-N-co-doped TiO{sub 2} photocatalyst was attributed to the large surface areas, narrow band gap and intense light absorbance in visible region. This study may create a promising and eco-friendly method towards synthesis of metal and non-metals co-doped on semiconductor materials to improve their photocatalytic activities and applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

3D printed Ni-Mn-Fe Bi-Functional Catalyst for Metal Air Batteries

Oxygen evolution catalyst with porous structures on the submillimeter and millimeter ranges have been shown to have high catalytic activity. Often, a limiting factor in the performance of a catalyst can be its specific surface area as this can limit the availability of active sites which encourage the desired reaction. As such, the inclusion of a hierarchical structure that include both meso-scale and nano-scale porosity can offer a means to greatly increase the performance of electrochemical catalysts. We have developed a method for manufacturing samples with such a hierarchical structure by combining techniques of direct ink writing (DIW), thermal sintering and free corrosion based dealloying. This allows us to prepare three-dimensionally structured samples with open-cell porosity at the macro-, micro- and nano-scales. Each level of porosity offers a different advantage to the overall functionality and applicability of this technology.

25 ENERGY STORAGE↗
DOE OSTI2017

Experimental study of microstructure changes due to low cycle fatigue of a steel nanocrystallised by Surface Mechanical Attrition Treatment (SMAT)

Electron Backscatter Diffraction technique is used to characterize the microstructure of 316L steel generated by Surface Mechanical Attrition Treatment (SMAT) before and after low cycle fatigue tests. A grain size gradient is generated from the top surface to the interior of the samples after SMAT so that three main regions can be distinguished below the treated surface: (i) the ultra-fine grain area within 5 μm under the top surface with preferably oriented grains, (ii) the intermediate area where the original grains are partially transformed, and (iii) the edge periphery area where the original grains are just mechanically deformed with the presence of plastic slips. Fatigue tests show that cyclic loading does not change the grain orientation spread and does not activate any plastic slip in the ultra-fine grain top surface area induced by SMAT. On the opposite, in the plastically SMAT affected region including the intermediate area and the edge periphery area, new slip systems are activated by low cycle fatigue while the grain orientation spread is increased. These results represent a first very interesting step towards the characterization and understanding of mechanical mechanisms involved during the fatigue of a grain size gradient material. - Highlights: •LCF tests are carried out on specimens processed by SMAT. •EBSD is used to investigate microstructural changes induced by LCF. •A grain size gradient is generated by SMAT from surface to the bulk of the fatigue samples. •New slip systems are activated by LCF and GOS is increased in plastically deformed region. •However, these phenomena are not observed in the top surface ultra-fine grain area.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Review—Development of Highly Active and Durable Hybrid Compressive Platinum Lattice Catalysts for Polymer Electrolyte Membrane Fuel Cells: Mathematical Modeling and Experimental Work

This review provides a comprehensive overview on the development of highly active and durable platinum catalysts with ultra-low Pt loadings for polymer electrolyte membrane fuel cells (PEMFCs) through a combined mathematical modeling and experimental work. First, simulation techniques were applied to evaluate the validity of the Tafel approximation for the calculation of the mass activity (MA) and specific activity (SA). A one-dimensional agglomeration model was developed and solved to understand the effects of exchange current density, porosity, agglomerate size, Nafion ® film thickness, and Pt loading on the MA and SA. High porosity (> 60%) and agglomerations at high Pt loadings cause the loss of the Tafel approximation and consequently the decrease in MA and SA. A new structure parameter was introduced to estimate the real porous structure using the fractal theory. The volumetric catalyst density was corrected by the fractal dimension (measured by Hg porosimetry), which gave a good agreement with the experimental values. The loading-dependent Tafel equation was then derived, which contains both the utilization and the non-linear scaling factor. Second, activated carbon composite support (ACCS) with optimized surface area, porosity, pore size, and pore size distribution was developed. The hydrophilic/hydrophobic ratio, structural properties (amorphous/crystalline ratio), and the number of active sites were optimized through metal-catalyzed pyrolysis. Stability of ACCS and Pt/ACCS were evaluated using an accelerated stress test (AST). The results indicated that Pt/ACCS showed no significant loss of MA and power density after 5,000 cycles at 1.0–1.5 V, while the commercial Pt/C catalysts showed drastic losses of MA and power density. Finally, monolayers of compressed Pt (core–shell-type Pt 3 Co 1 ) catalysts were structured by diffusing Co atoms (previously embedded in ACCS) into Pt. Compressive Pt lattice (Pt * ) catalysts were synthesized through an annealing procedure developed at the University of South Carolina (USC). The Pt * /ACCS catalyst showed high initial power density (rated) of 0.174 g Pt kW −1 and high stability (24 mV loss) at 0.8 A cm −2 after 30,000 cycles (0.6–1.0 V). The outstanding performance of Pt * /ACCS is due to the synergistic effect of ACCS and compressive Pt * lattice.

25 ENERGY STORAGE↗
NASA NTRS1991

Monolith catalysts for closed-cycle carbon dioxide lasers

The objective was to explore ways of making a monolithic form of catalyst for CO2 lasers. The approach chosen was to pelletize the catalyst material, Au/MnO2 powder, and epoxy the pellets to stainless steel sheets as structural supports. The CO oxidation reaction over Au/MnO2 powder was found to be first overall, and the reaction rate constant at room temperature was 4.4 +/- 0.3 cc/(g x sec). The activation energy was 5.7 kcal/mol. The BET surface area of the pellets was found to vary from 125 to 140 sq m/g between different batches of catalyst. Pellets epoxied to stainless steel strips showed no sign of fracture or dusting when subjected to thermal tests. Pellets can be dropped onto hard surfaces with chipping of edges but no breakage of the pellets. Mechanical strength tests performed on the pellets showed that the crush strength is roughly one-fourth of the pelletizing force. The apparent activity and activation energy over the pellets were found to be less than over the powdered form of the catalyst. The lower apparent activity and activation energy of the pellets are due to the fact that the internal surface area of a pellet is not exposed to the reactant concentration present in the flowing gas as a result of intrapellet diffusion resistance. Effectiveness factors varied from 0.44, for pellets having thickness of 2 mm and attached with epoxy to a stainless steel strip. The epoxy and the stainless steel strip were found to simply block off one of the circular faces of the pellets. The epoxy did not penetrate the pellets and block the active sites. The values of the effective diffusivities were estimated to be between 2.3 x 10(exp -3) and 4.9 x 10(exp -3) sq cm/s. With measurements performed on one powder sample and one pellet configuration, reasonable accurate predictions can be made of conversions that would be obtained with other pellet thickness and configurations.

Herz, Richard K.↗
NASA NTRS1973

Mission description

The accomplishments of the Apollo 17 flight are discussed. The scientific objectives included geological surveying and sampling of materials and surface features in a preselected area of the Taurus-Littrow region, deploying and activating surface experiments, and conducting inflight experiments and photographic tasks during lunar orbit and transearth coast. The individual Apollo 17 experiments and photographic tasks are presented in outline form. Charts are developed to show the major mission events and data collection periods correlated to Greenwich Mean Time and ground elapsed time. Maps of the lunar surface ground track envelope for the Apollo 17 orbiting spacecraft for revolutions one to seventy-five is shown.

Baldwin, R. R.↗
DOE OSTI2018

Solution processed metal-doped NiS/PEDOT:PSS composite thin films as an efficient electrode for quantum-dot sensitized solar cells

Highlights: • Metal-doped NiS/PEDOT:PSS chrysanthemum flower like structure was fabricated. • Deposition of PEDOT: PSS into Cu-NiS enhances the V{sub oc} and PCE. • Introduction of PEDOT: PSS acts as a passivation layer for reducing charge recombination. • Cu-NiS/PEDOT:PSS shows higher onset potential with higher limiting current density. - Abstract: Cu-doped NiS with PEDOT:PSS chrysanthemum flower-like structures, which were composed of many nanopetal bunches in a radial fashion, were synthesized using a modest, eco-friendly and cost effective method. The 5 wt.% Cuph/PEDOT:PSS produced a minute amount of PEDOT:PSS, which exhibiting outstanding electrochemical performance in QDSSCs. The synergetic effects of the composite were investigated and a PCE of 4.87%, fill factor of 0.51, J{sub sc} of 13.75 mA cm{sup −2}, and V{sub oc} of 0.549 V in a polysulfide electrolyte were obtained. The electrode exhibited great electrocatalytic activities and lower charge transfer resistance than that of the bare NiS and Cu-doped NiS, making it a promising material for both fuel cells and QDSSCs. The improved performance of the 5 wt.% Cuph/PEDOT:PSS electrode was attributed mainly to the large surface area, greater electrical conductivity and high electrocatalytic activity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Ice nucleating particles in the marine boundary layer in the Canadian Arctic during summer 2014

Ice nucleating particles (INPs) in the Arctic can influence climateand precipitation in the region; yet our understanding of the concentrations and sourcesof INPs in this region remain uncertain. In the following, we (1) measured concentrationsof INPs in the immersion mode in the Canadian Arctic marine boundary layer duringsummer 2014 on board the CCGS Amundsen , (2) determined ratios of surface areasof mineral dust aerosol to sea spray aerosol, and (3) investigated the source region ofthe INPs using particle dispersion modelling. Average concentrations of INPs at -15 , -20 , and -25 - C were 0.005, 0.044, and 0.154 L -1 ,respectively. These concentrations fall within the range of INP concentrations measuredin other marine environments. For the samples investigated the ratio of mineral dustsurface area to sea spray surface area ranged from 0.03 to 0.09. Based on these ratiosand the ice active surface site densities of mineral dust and sea spray aerosoldetermined in previous laboratory studies, our results suggest that mineral dust is amore important contributor to the INP population than sea spray aerosol for the samplesanalysed. Based on particle dispersion modelling, the highest concentrations of INPs wereoften associated with lower-latitude source regions such as the Hudson Bay area, easternGreenland, or north-western continental Canada. On the other hand, the lowestconcentrations were often associated with regions further north of the sampling sites andover Baffin Bay. A weak correlation was observed between INP concentrations and the timethe air mass spent over bare land, and a weak negative correlation was observed betweenINP concentrations and the time the air mass spent over ice and open water. Thesecombined results suggest that mineral dust from local sources is an important contributorto the INP population in the Canadian Arctic marine boundary layer during summer 2014.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Self-Supported Hydrous Iridium–Nickel Oxide Two-Dimensional Nanoframes for High Activity Oxygen Evolution Electrocatalysts

Oxygen evolution reaction (OER) electrocatalysts with high activity, high stability, and low costs are needed for proton-exchange membrane (PEM) electrolyzers. Based on the high cost and limited supply of iridium, approaches that result in iridium-based OER catalysts with increased catalytic activity are of significant interest. Here, we report a carbon-free, self-supported hydrous iridium-nickel oxide two-dimensional nanoframe structure synthesized by thermal treatment of iridium-decorated nickel oxide nanosheets under reducing conditions and subsequent chemical leaching in acid. The catalyst nanoarchitecture contains an interconnected network of metallic iridium-nickel alloy domains with hydrous iridium oxide and nickel oxide located in the surface region. The electrochemical oxidation step maintains the three-dimensional nanoarchitecture and results in a thin (~5 A) oxide/hydroxide surface layer. The temperature used for thermal reduction was found to strongly affect the catalyst surface structure and OER activity. Utilizing a lower thermal reduction temperature of 200 degrees C was determined to provide a higher relative surface concentration of hydroxides and nickel oxide and result in higher OER activities compared with materials treated at 300 degrees C. The 200 degrees C-treated hydrous iridium-nickel oxide electrocatalyst showed 15 times higher initial OER mass activity than commercial IrO 2 , and the activity remained 10 times higher than IrO 2 after accelerated durability testing. Density functional theory (DFT) calculations and analysis of the experimental Tafel slopes support that the second electron transfer step is the rate-limiting step for the reaction. The DFT calculations demonstrate that Ni substitution on the IrO 2 surface lowers the activation energy for adsorbed intermediates of the second electron transfer step of the OER reaction. This work establishes that noble metal-decorated metal oxide nanosheets can be transformed into high surface area, carbon-free electrocatalyst nanostructures with high catalytic activities and molecular accessibility and reveals the importance of using controlled thermal reduction temperatures to alter the surface structure and OER activity.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Vangl2 is essential for myocardial remodeling activated by Wnt/JNK signaling

Highlights: • Wnt5a triggered activation of JNK in time-dependent manner. • Activation of Wnt/JNK signaling stimulates myocardial remodeling. • Vangl2 knockdown partly reversed myocardial remodeling. The Wnt/JNK pathway, responsible for tissue polarity in cardiogenesis in vertebrates, has been shown to play numerous roles during differentiation and development of cardiac myocytes. Van Gogh-like-2 (Vangl2) is a core component that regulates the induction of polarized cellular and tissue morphology during animal development. However, little is known about Wnt/JNK signaling pathway in the process of myocardial remodeling. In present study, we found that activation of Wnt/JNK signaling by Wnt5a stimulates enlargement of cardiomyocyte surface area. The hypertrophic features were inhibited in Vangl2 depleted cells. Meanwhile, Wnt/JNK activation induced cytoskeleton rearrangement but failed to activate these effects in cells lacking Vangl2. Moreover, Wnt/JNK activation significantly increased the cell apoptosis by mediating the mitochondrial permeability transition pore (mPTP) dysfunction, whereas knockdown of Vangl2 partly reversed these effects. These results suggest that activation of Wnt/JNK signaling stimulates myocardial remodeling (cell morphological changes, apoptosis and mitochondrial dysfunction), in which Vangl2 may play an essential role.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Cellulose regulated lignin/cellulose-based carbon materials with hierarchical porous structure for energy storage

Lignin has gained extensive attention as an ideal carbon precursor due to its abundance and high carbon content. However, the agglomeration of lignin and additional corrosive and unrecyclable reagents in direct pyrolysis still limit the development of lignin-based porous carbons. Herein, a facile and eco-friendly strategy was proposed to fabricate hierarchical porous lignin/cellulose-based carbon materials (LCs). In the process, cellulose nanofibrils acted as the skeleton of the bio-aerogels, which supported lignin and benefit the preparation of the LCs. Moreover, the specific surface area and the graphitization degree of LCs can be regulated by varying the cellulose content. Without activation, the bio-based carbon material (LC30) had a high specific surface area of 1770 m 2 g –1 , which displayed high specific capacitance of 216.2 F g –1 at the current density of 0.5 A g –1 . The supercapacitor based on LC30 also showed outstanding energy density of 12.3 Wh kg –1 at the power density of 50 W kg –1 . The sustainable raw material, simple and harmless preparation process, and remarkable electrochemical performance enable LC30, a promising supercapacitor electrode for energy storage.

25 ENERGY STORAGE↗
DOE OSTI2018

Production of new activated bio-carbons by chemical activation of residue left after supercritical extraction of hops

Highlights: • An alternative method for bio-waste utilization has been proposed. • Activated bio-carbons were prepared from hops by Na{sub 2}CO{sub 3} activation. • The activated bio-carbons has been used for NO{sub 2}, methylene blue and iodine adsorption. A technology of activated bio-carbons production from the residue left after supercritical extraction of hops is described. The effect of the variant of chemical activation and impregnation ratio on the physicochemical properties as well as sorption capacity towards toxic gas of acidic character (nitrogen dioxide), basic organic dye (aqueous solution of methylene blue - MB) and iodine was investigated. The materials obtained were activated bio-carbons of well-developed surface area ranging between 897 and 1095 m{sup 2}/g, showing clearly acidic character of the surface. The sorption tests results proved that chemical activation of the residue left after supercritical extraction of hops allows obtaining activated bio-carbons with very high sorption capacity towards nitrogen dioxide, reaching to 77.2 and 155.3 mg/g in dry and wet conditions, respectively. The maximum sorption capacity of the adsorbents towards methylene blue was 328.75 mg/g, while towards iodine 1815 mg/g. The equilibrium data for aqueous solution of MB were analyzed by the Langmuir and Freundlich models, whereas the kinetics of the adsorption process was studied using pseudo-first and second-order models. According to the obtained data, the adsorption of MB from aqueous solution is better described by Langmuir model and pseudo-second order kinetic model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Visible-light H 2 evolution using dye-sensitized TiO 2 : effects of physicochemical properties of TiO 2 on excited carrier dynamics and activity

Dye-sensitized photocatalysts have emerged as promising materials for solar-driven water splitting due to their ability to utilize visible light, in contrast to conventional wide-band-gap semiconductors. However, the relationship between semiconductor properties and charge carrier dynamics remains insufficiently understood. In this study, we investigated Pt/TiO 2 systems sensitized with a visible-light-absorbing Ru(II) polypyridyl complex (RuP), focusing on how the crystal phase and specific surface area of TiO 2 influence excited carrier dynamics and H 2 evolution activity. To isolate the effects of TiO 2 properties, Pt and RuP loadings were standardized across samples. Emission lifetime analysis showed similarly efficient electron injection from RuP to TiO 2 in all cases, suggesting that injection efficiency does not account for observed differences in activity. Transient absorption measurements revealed that back electron transfer (BET) rates depended strongly on the TiO 2 phase, with anatase and P25 exhibiting slower BET and higher activity for H 2 evolution than rutile. The highest apparent quantum yield for H 2 evolution was 12.0% at 450 nm. Among anatase samples, larger surface areas correlated with higher activity, while smaller-area samples exhibited slower BET rates but still low H 2 evolution activity, implying a role for RuP dye–dye interactions in performance loss. This was further supported by improvements in H 2 evolution activity by lowering RuP loading or adding co-adsorbents. Overall, these results demonstrate that both BET suppression and control over RuP dye aggregation are essential for designing efficient dye-sensitized photocatalytic systems.

Harada, Kakeru [Institute of Science Tokyo (Japan)↗
DOE OSTI2018

Flexible and conductive waste tire-derived carbon/polymer composite paper as pseudocapacitive electrode

A method of making a supercapacitor from waste tires, includes the steps of providing rubber pieces and contacting the rubber pieces with a sulfonation bath to produce sulfonated rubber; pyrolyzing the sulfonated rubber to produce a tire-derived carbon composite comprising carbon black embedded in rubber-derived carbon matrix comprising graphitized interface portions; activating the tire-derived carbon composite by contacting the tire-derived carbon composite with a specific surface area-increasing composition to increase the specific surface area of the carbon composite to provide an activated tire-derived carbon composite; and, mixing the activated tire-derived carbon composite with a monomer and polymerizing the monomer to produce a redox-active polymer coated, activated tire-derived carbon composite. The redox-active polymer coated, activated tire-derived carbon composite can be formed into a film. An electrode and a supercapacitor are also disclosed.

42 ENGINEERING↗