This study reports the preparation of a set of hybrid materials consisting of molybdenum disulfide (MoS 2 ) nanopatches on reduced graphene oxide (rGO) nanosheets by microwave specific heating of graphene oxide and molecular molybdenum precursors followed by thermal annealing in 3% H 2 and 97% Ar. The microwave process converts graphene oxide to ordered rGO nanosheets that are sandwiched between uniform thin layers of amorphous molybdenum trisulfide (MoS 3 ). The subsequent thermal annealing converts the intermediate layers into MoS 2 nanopatches with two-dimensional layered structures whose defect density is tunable by controlling the annealing temperature at 250, 325 and 600 °C, respectively. All three MoS 2 /rGO samples and the MoS 3 /rGO intermediate after the microwave step show a high Li-ion intercalation capacity in the initial 10 cycles (over 519 mA h g MoSx −1 , ∼3.1 Li + ions per MoS 2 ) which is attributed to the small MoS 2 nanopatches in the MoS 2 /rGO hybrids while the effect of further S-rich defects is insignificant. In contrast, the Zn-ion storage properties strongly depend on the defects in the MoS 2 nanopatches. The highly defective MoS 2 /rGO hybrid prepared by annealing at 250 °C shows the highest initial Zn-ion storage capacity (∼300 mA h g MoSx −1 ) and close to 100% coulombic efficiency, which is dominated by pseudocapacitive surface reactions at the edges or defects in the MoS 2 nanopatches. The fast fading in the initial cycles can be mitigated by applying higher charge/discharge currents or extended cycles. This study validates that defect engineering is critical for improving Zn-ion storage.
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Design of highly porous Fe 3 O 4 @reduced graphene oxide via a facile PMAA-induced assembly
Advances in the synthesis and processing of graphene-based materials have presented the opportunity to design novel lithium-ion battery (LIB) anode materials that can meet the power requirements of next-generation power devices. In this work, a poly(methacrylic acid) (PMAA)-induced self-assembly process was used to design super-mesoporous Fe 3 O 4 and reduced-graphene-oxide (Fe 3 O 4 @RGO) anode materials. We demonstrate the relationship between the media pH and Fe 3 O 4 @RGO nanostructure, in terms of dispersion state of PMAA-stabilized Fe 3 O 4 @GO sheets at different surrounding pH values, and porosity of the resulted Fe 3 O 4 @RGO anode. The anode shows a high surface area of 338.8 m 2 g −1 with a large amount of 10–40 nm mesopores, which facilitates the kinetics of Li-ions and electrons, and improves electrode durability. As a result, Fe 3 O 4 @RGO delivers high specific-charge capacities of 740 mA h g −1 to 200 mA h g −1 at various current densities of 0.5 A g −1 to 10 A g −1 , and an excellent capacity-retention capability even after long-term charge–discharge cycles. The PMAA-induced assembly method addresses the issue of poor dispersion of Fe 3 O 4 -coated graphene materials—which is a major impediment in the synthesis process—and provides a facile synthetic pathway for depositing Fe 3 O 4 and other metal oxide nanoparticles on highly porous RGO.
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- Award ID(s):
- 1653527
- NSF-PAR ID:
- 10132538
- Date Published:
- Journal Name:
- RSC Advances
- Volume:
- 9
- Issue:
- 48
- ISSN:
- 2046-2069
- Page Range / eLocation ID:
- 27927 to 27936
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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For the first time, a fast heating–cooling process is reported for the synthesis of carbon‐coated nickel (Ni) nanoparticles on a reduced graphene oxide (RGO) matrix (nano‐Ni@C/RGO) as a high‐performance H2O2fuel catalyst. The Joule heating temperature can reach up to ≈2400 K and the heating time can be less than 0.1 s. Ni microparticles with an average diameter of 2 µm can be directly converted into nanoparticles with an average diameter of 75 nm. The Ni nanoparticles embedded in RGO are evaluated for electro‐oxidation performance as a H2O2fuel in a direct peroxide–peroxide fuel cell, which exhibits an electro‐oxidation current density of 602 mA cm−2at 0.2 V (vs Ag/AgCl), ≈150 times higher than the original Ni microparticles embedded in the RGO matrix (micro‐Ni/RGO). The high‐temperature, fast Joule heating process also leads to a 4–5 nm conformal carbon coating on the surface of the Ni nanoparticles, which anchors them to the RGO nanosheets and leads to an excellent catalytic stability. The newly developed nano‐Ni@C/RGO composites by Joule heating hold great promise for a range of emerging energy applications, including the advanced anode materials of fuel cells.
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Titanium carbide/reduced graphene oxide (Ti 3 C 2 T z /rGO) gels were prepared by a one-step hydrothermal process. The gels show a highly porous structure with a surface area of ∼224 m 2 g −1 and average pore diameter of ∼3.6 nm. The content of GO and Ti 3 C 2 T z nanosheets in the reaction precursor was varied to yield different microstructures. The supercapacitor performance of Ti 3 C 2 T z /rGO gels varied significantly with composition. Specific capacitance initially increased with increasing Ti 3 C 2 T z content, but at high Ti 3 C 2 T z content gels cannot be formed. Also, the retention of capacitance decreased with increasing Ti 3 C 2 T z content. Ti 3 C 2 T z /rGO gel electrodes exhibit enhanced supercapacitor properties with high potential window (1.5 V) and large specific capacitance (920 F g −1 ) in comparison to pure rGO and Ti 3 C 2 T z . The synergistic effect of EDLC from rGO and redox capacitance from Ti 3 C 2 T z was the reason for the enhanced supercapacitor performance. A symmetric two-electrode supercapacitor cell was constructed with Ti 3 C 2 T z /rGO, which showed very high areal capacitance (158 mF cm −2 ), large energy density (∼31.5 μW h cm −2 corresponding to a power density of ∼370 μW cm −2 ), and long stability (∼93% retention) after 10 000 cycles.more » « less
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Ever-increasing demands for energy, particularly being environmentally friendly have promoted the transition from fossil fuels to renewable energy.1Lithium-ion batteries (LIBs), arguably the most well-studied energy storage system, have dominated the energy market since their advent in the 1990s.2However, challenging issues regarding safety, supply of lithium, and high price of lithium resources limit the further advancement of LIBs for large-scale energy storage applications.3Therefore, attention is being concentrated on an alternative electrochemical energy storage device that features high safety, low cost, and long cycle life. Rechargeable aqueous zinc-ion batteries (ZIBs) is considered one of the most promising alternative energy storage systems due to the high theoretical energy and power densities where the multiple electrons (Zn2+) . In addition, aqueous ZIBs are safer due to non-flammable electrolyte (e.g., typically aqueous solution) and can be manufactured since they can be assembled in ambient air conditions.4As an essential component in aqueous Zn-based batteries, the Zn metal anode generally suffers from the growth of dendrites, which would affect battery performance in several ways. Second, the led by the loose structure of Zn dendrite may reduce the coulombic efficiency and shorten the battery lifespan.5
Several approaches were suggested to improve the electrochemical stability of ZIBs, such as implementing an interfacial buffer layer that separates the active Zn from the bulk electrolyte.6However, the and thick thickness of the conventional Zn metal foils remain a critical challenge in this field, which may diminish the energy density of the battery drastically. According to a theretical calculation, the thickness of a Zn metal anode with an areal capacity of 1 mAh cm-2is about 1.7 μm. However, existing extrusion-based fabrication technologies are not capable of downscaling the thickness Zn metal foils below 20 μm.
Herein, we demonstrate a thickness controllable coating approach to fabricate an ultrathin Zn metal anode as well as a thin dielectric oxide separator. First, a 1.7 μm Zn layer was uniformly thermally evaporated onto a Cu foil. Then, Al2O3, the separator was deposited through sputtering on the Zn layer to a thickness of 10 nm. The inert and high hardness Al2O3layer is expected to lower the polarization and restrain the growth of Zn dendrites. Atomic force microscopy was employed to evaluate the roughness of the surface of the deposited Zn and Al2O3/Zn anode structures. Long-term cycling stability was gauged under the symmetrical cells at 0.5 mA cm-2for 1 mAh cm-2. Then the fabricated Zn anode was paired with MnO2as a full cell for further electrochemical performance testing. To investigate the evolution of the interface between the Zn anode and the electrolyte, a home-developed in-situ optical observation battery cage was employed to record and compare the process of Zn deposition on the anodes of the Al2O3/Zn (demonstrated in this study) and the procured thick Zn anode. The surface morphology of the two Zn anodes after circulation was characterized and compared through scanning electron microscopy. The tunable ultrathin Zn metal anode with enhanced anode stability provides a pathway for future high-energy-density Zn-ion batteries.
Obama, B., The irreversible momentum of clean energy.
Science 2017, 355 (6321), 126-129.Goodenough, J. B.; Park, K. S., The Li-ion rechargeable battery: a perspective.
J Am Chem Soc 2013, 135 (4), 1167-76.Li, C.; Xie, X.; Liang, S.; Zhou, J., Issues and Future Perspective on Zinc Metal Anode for Rechargeable Aqueous Zinc‐ion Batteries.
Energy & Environmental Materials 2020, 3 (2), 146-159.Jia, H.; Wang, Z.; Tawiah, B.; Wang, Y.; Chan, C.-Y.; Fei, B.; Pan, F., Recent advances in zinc anodes for high-performance aqueous Zn-ion batteries.
Nano Energy 2020, 70 .Yang, J.; Yin, B.; Sun, Y.; Pan, H.; Sun, W.; Jia, B.; Zhang, S.; Ma, T., Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives.
Nanomicro Lett 2022, 14 (1), 42.Yang, Q.; Li, Q.; Liu, Z.; Wang, D.; Guo, Y.; Li, X.; Tang, Y.; Li, H.; Dong, B.; Zhi, C., Dendrites in Zn-Based Batteries.
Adv Mater 2020, 32 (48), e2001854.Acknowledgment
This work was partially supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 22011044) by KRISS.
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Abstract The growing demand for bioelectronics has generated widespread interest in implantable energy storage. These implantable bioelectronic devices, powered by a complementary battery/capacitor system, have faced difficulty in miniaturization without compromising their functionality. This paper reports on the development of a promising high‐rate cathode material for implantable power sources based on Li‐exchanged Na1.5VOPO4F0.5anchored on reduced graphene oxide (LNVOPF‐rGO). LNVOPF is unique in that it offers dual charge storage mechanisms, which enable it to exhibit mixed battery/capacitor electrochemical behavior. In this work, electrochemical Li‐ion exchange of the LNVOPF structure is characterized by operando X‐ray diffraction. Through designed nanostructuring, the charge storage kinetics of LNVOPF are improved, as reflected in the stored capacity of 107 mAh g−1at 20C. A practical full cell device composed of LNVOPF and T‐Nb2O5, which serves as a pseudocapacitive anode, is fabricated to demonstrate not only high energy/power density storage (100 Wh kg−1at 4000 W kg−1) but also reliable pulse capability and biocompatibility, a desirable combination for applications in biostimulating devices. This work underscores the potential of miniaturizing biomedical devices by replacing a conventional battery/capacitor couple with a single power source.
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9ra04980k
