skip to main content

Title: Phase transformation and electrochemical charge storage properties of vanadium oxide/carbon composite electrodes synthesized via integration with dopamine
Chemically preintercalated dopamine (DOPA) molecules were used as both reducing agent and carbon precursor to prepare δ-V2O5∙nH2O/C, H2V3O8/C, VO2(B)/C and V2O3/C nanocomposites via hydrothermal treatment or hydrothermal treatment followed by annealing under Ar flow. We found that the phase composition and morphology of the produced composites are influenced by the DOPA:V2O5 ratio used to synthesize (DOPA)xV2O5 precursors through DOPA diffusion into the interlayer region of δ-V2O5∙nH2O framework. The increase of DOPA concentration in the reaction mixture led to more pronounced reduction of vanadium and a higher fraction of carbon in the composites’ structure, as evidenced by XPS and Raman spectroscopy measurements. The electrochemical charge storage properties of the synthesized nanocomposites were evaluated in Li-ion cells with non-aqueous electrolyte. δ-V2O5∙nH2O/C, H2V3O8/C, VO2(B)/C, and V2O3/C electrodes delivered high initial capacities of 214, 252, 279, and 637 mAh·g–1, respectively. The insights provided by this investigation open up the possibility of creating new nanocomposite oxide/carbon electrodes for a variety of applications such as energy storage, sensing and electrochromic devices.
; ;
Award ID(s):
1752623 1609272
Publication Date:
Journal Name:
Journal of the American Ceramic Society
Sponsoring Org:
National Science Foundation
More Like this
  1. A capacitance increase phenomenon is observed for MoO 3 electrodes synthesized via a sol-gel process in the presence of dopamine hydrochloride (Dopa HCl) as compared to α-MoO 3 electrodes in 5M ZnCl 2 aqueous electrolyte. The synthesis approach is based on a hydrogen peroxide-initiated sol-gel reaction to which the Dopa HCl is added. The powder precursor (Dopa) x MoO y , is isolated from the metastable gel using freeze-drying. Hydrothermal treatment (HT) of the precursor results in the formation of MoO 3 accompanied by carbonization of the organic molecules; designated as HT-MoO 3 /C. HT of the precipitate formed in the absence of dopamine in the reaction produced α-MoO 3 , which was used as a reference material in this study (α-MoO 3 -ref). Scanning electron microscopy (SEM) images show a nanobelt morphology for both HT-MoO 3 /C and α-MoO 3 -ref powders, but with distinct differences in the shape of the nanobelts. The presence of carbonaceous content in the structure of HT-MoO 3 /C is confirmed by FTIR and Raman spectroscopy measurements. X-ray diffraction (XRD) and Rietveld refinement analysis demonstrate the presence of α-MoO 3 and h-MoO 3 phases in the structure of HT-MoO 3 /C. The increased specificmore »capacitance delivered by the HT-MoO 3 /C electrode as compared to the α-MoO 3 -ref electrode in 5M ZnCl 2 electrolyte in a −0.25–0.70 V vs. Ag/AgCl potential window triggered a more detailed study in an expanded potential window. In the 5M ZnCl 2 electrolyte at a scan rate of 2 mV s −1 , the HT-MoO 3 /C electrode shows a second cycle capacitance of 347.6 F g −1 . The higher electrochemical performance of the HT-MoO 3 /C electrode can be attributed to the presence of carbon in its structure, which can facilitate electron transport. Our study provides a new route for further development of metal oxides for energy storage applications.« less
  2. Nanoporous bimetallic Fe–Ag nanoparticles (NPs) were synthesized using a facile chemical reduction method and used to decorate the surface of multi-walled carbon nanotubes (MWCNTs) for hydrogen sorption and storage. The effect of TiO 2 nanoparticles on the hydrogen storage properties of Fe–Ag/CNTs was further studied in detail. For this purpose, several nanocomposites of nanoporous bimetallic Fe–Ag/TiO 2 nanoparticles with different amounts of bimetallic Fe–Ag NPs were prepared via a hydrothermal method. The hydrogen storage capacity of the as-prepared nanocomposites was studied using electrochemical methods. The Fe–Ag/TiO 2 /CNT nanocomposite with 0.04 M bimetallic Fe–Ag NPs showed the highest capacity for hydrogen storage, which was ∼5× higher than that of pristine MWCNTs. The maximum discharge capacity was 2931 mA h g −1 , corresponding to a 10.94 wt% hydrogen storage capacity. Furthermore, a 379% increase in discharge capacity was measured after 20 cycles. These results show that Fe–Ag/TiO 2 /CNT electrodes display superior cycling stability and high reversible capacity, which is attractive for battery applications.
  3. In this work, we designed and fabricated a nanoscopic sugar-based magnetic hybrid material that is capable of tackling environmental pollution posed by marine oil spills, while minimizing potential secondary problems that may occur from microplastic contamination. These readily-defined magnetic nanocomposites were constructed through co-assembly of magnetic iron oxide nanoparticles (MIONs) and a degradable amphiphilic polymer, poly(ethylene glycol)- b -dopamine-functionalized poly(ethyl propargyl glucose carbonate)- b -poly(ethyl glucose carbonate), PEG- b -PGC[(EPC-MPA)- co -(EPC-DOPA)]- b -PGC(EC), driven by supramolecular co-assembly in water with enhanced interactions provided via complexation between dopamine and MIONs. The composite nanoscopic assemblies possessed a pseudo -micellar structure, with MIONs trapped within the polymer framework. The triblock terpolymer was synthesized by sequential ring-opening polymerizations (ROPs) of two glucose-derived carbonate monomers, initiated by a PEG macroinitiator. Dopamine anchoring groups were subsequently installed by first introducing carboxylic acid groups using a thiol–yne click reaction, followed by amidation with dopamine. The resulting amphiphilic triblock terpolymers and MIONs were co-assembled to afford hybrid nanocomposites using solvent exchange processes from organic solvent to water. In combination with hydrophobic interactions, the linkage between dopamine and iron oxide stabilized the overall nanoscopic structure to allow for the establishment of a uniform globular morphology, whereas attempts atmore »co-assembly with the triblock terpolymer precursor, lacking dopamine side chains, failed to afford well-defined nanostructures. The magnetic hybrid nanoparticles demonstrated high oil sorption capacities, ca. 8 times their initial dry weight, attributed, in part, to large surface areas leading to effective contact between the nanomaterials and hydrocarbon pollutants. Moreover, the naturally-derived polymer framework undergoes hydrolytic degradation to break down into byproducts that include glucose, ethanol and dopamine if not recovered after deployment, alleviating concerns of potential microplastic generation and persistence.« less
  4. Carbon-based nanocomposites have been attracting extensive attention as high-performance catalysts in alkaline media towards the electrochemical reduction of oxygen. Herein, polyacrylonitrile nanoflowers are synthesized via a free-radical polymerization route and used as a structural scaffold and precursor, whereby controlled pyrolysis leads to the ready preparation of carbon nanocomposites (FeNi-NCF) doped with both metal (Fe and Ni) and nonmetal (N) elements. Transmission electron microscopy studies show that the FeNi-NCF composites retain the flower-like morphology, with the metal species atomically dispersed into the flaky carbon petals. Remarkably, despite a similar structure, elemental composition, and total metal content, the FeNi-NCF sample with a high Fe:Ni ratio exhibits an electrocatalytic performance towards oxygen reduction reaction (ORR) in alkaline media that is similar to that by commercial Pt/C, likely due to the Ni to Fe electron transfer that promotes the adsorption and eventual reduction of oxygen, as evidenced in X-ray photoelectron spectroscopic measurements. Results from this study underline the importance of the electronic properties of metal dopants in the manipulation of the ORR activity of carbon nanocomposites.
  5. Subduction zones represent the interface between Earth’s interior (crust and mantle) and exterior (atmosphere and oceans), where carbon and other volatile elements are actively cycled between Earth reservoirs by plate tectonics. Helium is a sensitive tracer of volatile sources and can be used to deconvolute mantle and crustal sources in arcs; however it is not thought to be recycled into the mantle by subduction processes. In contrast, carbon is readily recycled, mostly in the form of carbon-rich sediments, and can thus be used to understand volatile delivery via subduction. Further, carbon is chemically-reactive and isotope fractionation can be used to determine the main processes controlling volatile movements within arc systems. Here, we report helium isotope and abundance data for 42 deeply-sourced fluid and gas samples from the Central Volcanic Zone (CVZ) and Southern Volcanic Zone (SVZ) of the Andean Convergent Margin (ACM). Data are used to assess the influence of subduction parameters (e.g., crustal thickness, subduction inputs, and convergence rate) on the composition of volatiles in surface volcanic fluid and gas emissions. He isotopes from the CVZ backarc range from 0.1 to 2.6 R A ( n = 23), with the highest values in the Puna and the lowest inmore »the Sub-Andean foreland fold-and-thrust belt. Atmosphere-corrected He isotopes from the SVZ range from 0.7 to 5.0 R A ( n = 19). Taken together, these data reveal a clear southeastward increase in 3 He/ 4 He, with the highest values (in the SVZ) falling below the nominal range associated with pure upper mantle helium (8 ± 1 R A ), approaching the mean He isotope value for arc gases of (5.4 ± 1.9 R A ). Notably, the lowest values are found in the CVZ, suggesting more significant crustal inputs (i.e., assimilation of 4 He) to the helium budget. The crustal thickness in the CVZ (up to 70 km) is significantly larger than in the SVZ, where it is just ∼40 km. We suggest that crustal thickness exerts a primary control on the extent of fluid-crust interaction, as helium and other volatiles rise through the upper plate in the ACM. We also report carbon isotopes from ( n = 11) sites in the CVZ, where δ 13 C varies between −15.3‰ and −1.2‰ [vs. Vienna Pee Dee Belemnite (VPDB)] and CO 2 / 3 He values that vary by over two orders of magnitude (6.9 × 10 8 –1.7 × 10 11 ). In the SVZ, carbon isotope ratios are also reported from ( n = 13) sites and vary between −17.2‰ and −4.1‰. CO 2 / 3 He values vary by over four orders of magnitude (4.7 × 10 7 –1.7 × 10 12 ). Low δ 13 C and CO 2 / 3 He values are consistent with CO 2 removal (e.g., calcite precipitation and gas dissolution) in shallow hydrothermal systems. Carbon isotope fractionation modeling suggests that calcite precipitation occurs at temperatures coincident with the upper temperature limit for life (122°C), suggesting that biology may play a role in C-He systematics of arc-related volcanic fluid and gas emissions.« less