Engineering topics

Liu, Wenwen

Publications and source records attributed to Liu, Wenwen.

5 records

DOE OSTI2024

Engineered MXene quantum dots for micro-supercapacitors with excellent capacitive behaviors

Micro-supercapacitors (MSCs) have drawn tremendous attention as promising candidates to power miniaturized portable/wearable electronics, but they still suffer from unsatisfactory electrochemical performance (e.g., insufficient energy density, mediocre rate capability), thus impeding their widespread applications. Here, a synergistic surface and structure engineering strategy achieved by downsizing to quantum dot scale, doping of heteroatoms, and introducing defects and functional groups is proposed to regulate the physicochemical properties of Ti 3 C 2 T x MXene. Encouragingly, the resulting MSCs based on defect-rich nitrogen-doped Ti 3 C 2 T x quantum dots (QDs) possess excellent electrochemical performance as demonstrated by large operating voltage (3.0 V in ionic liquid and 1.0 V in aqueous electrolyte), perfect rectangular CV shape even at 1000 V·s -1 , high volumetric capacitance of 33.1 F·cm -3 , and superior cycling stability after 10000 cycles. By employing experimental characterizations and density functional theory calculations, the remarkable performance of the MSCs is mainly due to the special chemical states as well as the unique surface and structural features of Ti 3 C 2 T x QDs, which offer abundant active sites, shorten ion diffusion pathways, promote ion/electron transports, and provide enhanced capacitance. Finally, this work provides a new strategy for the design of high-performance MSCs and a reference for the applications of MXene QDs in other energy-related fields.

42 ENGINEERING↗

DOE OSTI2022

Evidence of Morphological Change in Sulfur Cathodes upon Irradiation by Synchrotron X-rays

While the development of lithium–sulfur battery cathodes has benefited substantially from the use of in situ and ex situ X-ray absorption studies, the degree of undesired influence from synchrotron radiation has not been studied. In this study, we present evidence of severe beam damage on sulfur cathodes under irradiation by synchrotron X-rays. Specifically, X-ray fluorescence mapping with relatively low dosage was conducted to observe the morphological changes after conducting X-ray absorption spectroscopy (XAS). Under open-circuit conditions, the morphology of the sulfur spontaneously changes and tends to migrate out of the region of XAS sampling. Our work indicates that effort should be placed in first obtaining a no-change/stable open-circuit baseline when attempting to conduct in operando studies of lithium–sulfur batteries using synchrotron radiation with an energy of <7.7 keV and a flux of >6 × 10 12 photons s –1 .

25 ENERGY STORAGE↗

DOE OSTI2021

3d-Orbital Occupancy Regulated Ir-Co Atomic Pair Toward Superior Bifunctional Oxygen Electrocatalysis

Atomically dispersed metal catalysts are hailed as the most promising catalyst category for oxygen electrocatalysis. However, the challenges in regulating electronic configuration and unveiling the mechanism on the atomic scale are hindering their practical implementation. Herein, we modulate the Co d-orbital electron configuration by constructing the Ir–Co atomic pair toward boosted bifunctional activity. The as-developed dual-atom IrCo–N–C catalyst displays unprecedented activity with a half-wave potential of 0.911 V for oxygen reduction reaction and only 330 mV overpotential at 10 mA cm –2 for oxygen evolution reaction, outperforming the single-atom counterparts as well as the commercial Pt/C and Ir/C benchmarks. The impressive bifunctionality is also verified in a Zn–air battery prototype with an ultra-high cyclability over 450 cycles. Furthermore, theoretical calculations are performed to shed light on the synergetic effects of the atomic pair site, where the incorporation of Ir atom alters the d-orbital energy level of Co and thus induces the re-arrangement of d-electron toward intensified spin polarization. As a result, the lower occupancy of d z 2 orbital facilitates the electron acceptation from oxygen to form a stronger Co–O σ bond, thereby propelling faster reaction kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Developing high safety Li-metal anodes for future high-energy Li-metal batteries: strategies and perspectives

Developing high-safety Li-metal anodes (LMAs) is extremely important for the application of high-energy Li-metal batteries (LMBs), especially Li–S and Li–O 2 battery systems. However, the notorious Li-dendrite growth problem results in serious safety concerns for any energy storage application. Through a recent combination of interface-based science, nanotechnology-based solutions and characterization methods, the LMA is now primed for a technological boom. In this review, the recent emerging strategies and perspectives on LMAs are summarized, following which the current huge evolution in interfacial chemistry regulation, optimizing electrolyte components, designing a rational ‘host’ for lithium metal, optimizing “solid-state electrolytes” and other emerging strategies for developing high-safety LMAs is highlighted. Furthermore, several state-of-the-art in situ/operando synchrotron-based X-ray techniques for high safety LMB research are introduced. With the further development of LMAs in the future, subsequent application in high energy LMBs is to be expected.

25 ENERGY STORAGE↗

DOE OSTI2020

Ribavirin targets sugar transporter 6 to suppress acquisition and transmission of rice stripe tenuivirus by its vector Laodelphax striatellus

Abstract BACKGROUND Rice stripe tenuivirus (RSV) is one of the most destructive pathogens of rice and other cereal crops. The virus is transmitted by the small brown planthopper (SBPH, Laodelphax striatellus ) in a circulative‐propagative manner. Thus, blocking transmission by the insect vector would provide an effective strategy to prevent epidemic outbreaks of the disease. RESULTS In this study, we explored the effect of ribavirin on acquisition and transmission of the virus by specifically inhibiting the expression of sugar transporter 6 (LsSt‐6), which was recently reported as a key vector component for RSV transmission. Ribavirin at the highest concentration tested (250 μmol L ‐1 ) significantly reduced RSV acquisition and transmission efficiency by SBPHs through inhibiting LsSt‐6 messenger RNA (mRNA) level. Survival of the model insect Spodoptera frugiperda cell line (Sf9) was 95.0 ± 2.2 and 85.6 ± 2.1% after exposure to 250 μmol L ‐1 ribavirin or 8‐azaguanine, respectively. Further study confirmed that 250 μmol L ‐1 ribavirin also significantly reduced LsSt‐6 mRNA and protein levels in Sf9 cells. However, 8‐azaguanine did not significantly inhibit viral infectivity and LsSt‐6 mRNA levels in SBPH or the Sf9 cell line. CONCLUSION This result provides evidence that ribavirin has the potential to disrupt LsSt‐6 expression but not others like viral RNAs to prevent acquiring RSV, which leads to less viral accumulation in SBPH tissues and thereby lower transmission efficiency. © 2020 Society of Chemical Industry

Hajano, Jamal‐U‐Ddin↗