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Dong, Pei

Publications and source records attributed to Dong, Pei.

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Direct conversion of methane to aromatics and hydrogen via a heterogeneous trimetallic synergistic catalyst

Abstract Non-oxidative methane dehydro-aromatization reaction can co-produce hydrogen and benzene effectively on a molybdenum-zeolite based thermochemical catalyst, which is a very promising approach for natural-gas upgrading. However, the low methane conversion and aromatics selectivity and weak durability restrain the realistic application for industry. Here, a mechanism for enhancing catalysis activity on methane activation and carbon-carbon bond coupling has been found to promote conversion and selectivity simultaneously by adding platinum–bismuth alloy cluster to form a trimetallic catalyst on zeolite (Pt-Bi/Mo/ZSM-5). This bimetallic alloy cluster has synergistic interaction with molybdenum: the formed CH 3 * from Mo 2 C on the external surface of zeolite can efficiently move on for C-C coupling on the surface of Pt-Bi particle to produce C 2 compounds, which are the key intermediates of oligomerization. This pathway is parallel with the catalysis on Mo inside the cage. This catalyst demonstrated 18.7% methane conversion and 69.4% benzene selectivity at 710 °C. With 95% methane/5% nitrogen feedstock, it exhibited robust stability with slow deactivation rate of 9.3% after 2 h and instant recovery of 98.6% activity after regeneration in hydrogen. The enhanced catalytic activity is strongly associated with synergistic interaction with Mo and ligand effects of alloys by extensive mechanism studies and DFT calculation.

03 NATURAL GAS↗
DOE OSTI2024

Intelligent Electrochemical Sensors for Precise Identification of Volatile Organic Compounds Enabled by Neural Network Analysis

The volatile organic compounds (VOCs) in a wide spectrum of categories were identified as biomarkers in aquatic environments, playing an important role in marine and freshwater ecology and global atmospheric chemistry. VOCs released from biofuel have also attracted increasing attention. Although the importance has been recognized, the portable detection and analysis methods of VOC in aquatic systems have not yet been well developed and understood. Here, in this work, we innovatively proposed an intelligent electrochemical sensing approach to classify and quantify VOCs in solution. Utilizing the cyclic voltammetry (CV) method with an ionic liquid (IL)-based electrolyte, we analyzed 50 μL samples of various VOC analytes, including acetic acid (AC), acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, formaldehyde, formic acid, methanol, methyl formate (MF), toluene, and a formaldehyde-methanol mixture, along with deionized water (DI water). The generated voltammograms were subsequently analyzed using our uniquely designed and optimized 1-D convolutional neural network (1D-CNN). This deep-learning algorithm achieved a 99.09% accuracy in VOC classification validated through fivefold cross-validation and demonstrated an impressive 94.4% test accuracy for methanol detection within a 10 μL error range. For quantification, the system accurately categorized methanol volumes ranging from 0 to 50 μL in 10 μL increments, achieving a 98.18% accuracy. A notable linear correlation (R2 = 95.56%) was found between max current density at the oxidation peak and methanol volume, with the limit of detection (LOD) at 9.3 μL. Such a sensing method exhibits potential for portability, high accuracy, and generalization in the classification and quantification, ultimately reshaping the realm of VOC analysis in solution.

42 ENGINEERING↗
DOE OSTI2024

Covalently-Bonded Laminar Assembly of Van der Waals Semiconductors with Polymers: Toward High-Performance Flexible Devices

Van der Waals semiconductors (vdWS) offer superior mechanical and electrical properties and are promising for flexible microelectronics when combined with polymer substrates. However, the self-passivated vdWS surfaces and their weak adhesion to polymers tend to cause interfacial sliding and wrinkling, and thus, are still challenging the reliability of vdWS-based flexible devices. Here, in this study, an effective covalent vdWS–polymer lamination method with high stretch tolerance and excellent electronic performance is reported. Using molybdenum disulfide (MoS 2 ) and polydimethylsiloxane (PDMS) as a case study, gold–chalcogen bonding and mercapto silane bridges are leveraged. The resulting composite structures exhibit more uniform and stronger interfacial adhesion. This enhanced coupling also enables the observation of a theoretically predicted tension-induced band structure transition in MoS 2 . Moreover, no obvious degradation in the devices’ structural and electrical properties is identified after numerous mechanical cycle tests. This high-quality lamination enhances the reliability of vdWS-based flexible microelectronics, accelerating their practical applications in biomedical research and consumer electronics.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Impact of Pressure Distribution and Magnitude on the Performance of Lithium Metal Anodes

Li metal anodes are a critical battery technology due to their ability to substantially increase the energy density of Li-based batteries. It is well known that pressure greatly impacts the performance of a Li-metal anode. However, precisely how the pressure value and distribution of pressure affect performance is unclear. Furthermore, the solid-electrolyte interphase composition that forms under varying pressure distributions remains a key parameter for practical lithium metal anodes. In this work, different pressure distributions were employed by using differently shaped and oriented mechanical springs in the coin cells, resulting in varying contact points. Pressure-sensitive films were used to spatially map the pressure and correlate it to the performance. It was found that higher average pressure does not necessarily have a positive effect on performance. When high pressure is paired with poor pressure uniformity, the performance is in fact worse likely due to the current focusing effect, rendering unsatisfied cycling stability. This work points to the importance of controlling the relationship between average pressure and pressure uniformity.

25 ENERGY STORAGE↗
DOE OSTI2023

Species-Selective Detection of Volatile Organic Compounds by Ionic Liquid-Based Electrolyte Using Electrochemical Methods

The detection of volatile organic compounds (VOCs) is an important topic for environmental safety and public health. However, the current commercial VOC detectors suffer from cross-sensitivity and low reproducibility. In this work, we present species-selective detection for VOCs using an electrochemical cell based on ionic liquid (IL) electrolytes with features of high selectivity and reliability. The voltammograms measured with the IL-based electrolyte absorbing different VOCs exhibited species-selective features that were extracted and classified by linear discriminant analysis (LDA). The detection system could identify as many as four types of VOCs, including methanol, ethanol, acetone, formaldehyde, and additional water. A mixture of methanol and formaldehyde was detected as well. The sample required for the VOCs classification system was 50 μL, or 1.164 mmol, on average. The response time for each VOC measurement is as fast as 24 s. The volume of VOCs such as formaldehyde in solution could also be quantified by LDA and electrochemical impedance spectroscopy techniques, respectively. The system showed a tunable detection range for 1.6 and 16% (w/v) CH 2 O solution by adjusting the composition of the electrolyte. The limit of detection was as low as 1 μL. For the 1.6% CH 2 O solution, the linearity calibration range was determined to be from 5.30 to 53.00 μmol with a limit of detection at 0.53 μmol. The mechanisms for VOCs determination and quantification are also thoroughly discussed. Finally, it is expected that this work could provide a new insight into the concept of electrochemical detection of VOCs with machine learning analysis and be applied to both VOCs gas monitoring and fluid detection.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Superior photodynamic effect of single-walled carbon nanotubes in aprotic media: a kinetic study

It has been confirmed that single-walled carbon nanotubes (SWCNTs) could generate reactive oxygen species in aprotic media by utilizing photon energy. However, the impact of photon irradiation on SWCNTs and the kinetics of the generation process in aprotic media are still unclear, which significantly limits the yield performance. In this work, the kinetics for photodynamic effects has been investigated by performing characterizations on ultraviolet-treated SWCNTs using Raman spectroscopy, conductive atomic force microscope (in-situ), kelvin probe force microscope, and X-ray photoelectron spectroscopy. It is found that ultraviolet-treated SWCNTs are observed to have more defects, lower conductivity, and less surface charge after energy conversion. Starting from the fundamental intrinsic properties of SWCNTs, the kinetics and formation of these changes are thoroughly discussed. It turns out that the dispersion, chirality, and structural integrity of SWCNTs are important for achieving high-performance photodynamic effects, which are validated using several different SWCNTs as well as other carbon nanomaterials. A type of (6,5) s-SWCNTs exhibited the highest energy efficiency among a variety of other carbon nanomaterials. The yield rate is 2.15 mM/h, and the energy consumption is determined to be 2.79 W∙h/mM. This work is expected to help dramatically boost the energy efficiency of the photodynamic effect in aprotic media and pave the way for designing high-performance carbon nanomaterial-based photoinduced devices.

36 MATERIALS SCIENCE↗
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 OSTI2022

Recent Advances in 3D Printed Sensors: Materials, Design, and Manufacturing

Sensors are of great importance in different aspects of research and industry. Future sensors will require high-efficient and low-cost manufacturing, as well as high-performance functionality in areas, such as mechanical sensing, biomedical, and optical applications. Recent advances in 3D printing open a new paradigm for sensors fabrication as a precision, customizable, and seamless process. Here, in this article, the state-of-the-art 3D printing methods in sensors manufacturing is reviewed and the performance of the 3D printed sensing materials and devices is summarized. Special attention is paid to emerging multimaterial printing and 4D printing technologies, which will benefit the fabrication of a new generation of structures with multifunctionalities. The content on 3D printed sensors covers piezoelectric sensors, medical, and optical sensing devices. The performance of 3D printed sensors in comparison with the sensors made by traditional manufacturing is also covered. Finally, section 4 provides the viewpoints on the future development of 3D printed sensors.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Discovery of Graphene-Water Membrane Structure: Toward High-Quality Graphene Process

It is widely accepted that solid-state membranes are indispensable media for the graphene process, particularly transfer procedures. But these membranes inevitably bring contaminations and residues to the transferred graphene and consequently compromise the material quality. This study reports a newly observed free-standing graphene-water membrane structure, which replaces the conventional solid-state supporting media with liquid film to sustain the graphene integrity and continuity. Experimental observation, theoretical model, and molecular dynamics simulations consistently indicate that the high surface tension of pure water and its large contact angle with graphene are essential factors for forming such a membrane structure. More interestingly, water surface tension ensures the flatness of graphene layers and renders high transfer quality on many types of target substrates. This report enriches the understanding of the interactions on reduced dimensional material while rendering an alternative approach for scalable layered material processing with ensured quality for advanced manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Functionalized separator for next-generation batteries

Advancements in battery technology have dramatically increased demand for improvements in separator design, as the separator plays a critical role in ensuring the safety and electrochemical performance of the cells. Current separators, either in commercial usage or under investigation, have yet to meet the high stability and lifespan performance standards necessary to prevent deterioration in the efficiency and reliability of the battery technologies. Recently, considerable effort has been devoted to developing functionalized separators, ranging from designing a variety of new materials and modification methods, and increasingly, to optimizing advanced preparation processes. In order to understand how the mechanisms of separator performance are affected by different properties, we will first summarize recent research progress and then have in-depth discussions regarding the separator's significant contribution to enhancing the safety and performance of the cell. Additionally, we then provide our design strategy for future separators, which not only meets the requirements of different type of batteries, but also aims for multifunctionality. We hope such a perspective could provide new inspiration in the development of separator research for future battery technologies.

25 ENERGY STORAGE↗