The Dopamine Assisted Synthesis of MoO3/Carbon Electrodes With Enhanced Capacitance in Aqueous Electrolyte

Abstract

A capacitance increase phenomenon is observed for MoO3 electrodes synthesized via a sol-gel process in the presence of dopamine hydrochloride (Dopa HCl) as compared to α-MoO3 electrodes in 5M ZnCl2 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)xMoOy, is isolated from the metastable gel using freeze-drying. Hydrothermal treatment (HT) of the precursor results in the formation of MoO3 accompanied by carbonization of the organic molecules; designated as HT-MoO3/C. HT of the precipitate formed in the absence of dopamine in the reaction produced α-MoO3, which was used as a reference material in this study (α-MoO3-ref). Scanning electron microscopy (SEM) images show a nanobelt morphology for both HT-MoO3/C and α-MoO3-ref powders, but with distinct differences in the shape of the nanobelts. The presence of carbonaceous content in the structure of HT-MoO3/C is confirmed by FTIR and Raman spectroscopy measurements. X-ray diffraction (XRD) and Rietveld refinement analysis demonstrate the presence of α-MoO3 and h-MoO3 phases in the structure of HT-MoO3/C. The increased specific capacitance delivered by the HT-MoO3/C electrode as compared to the α-MoO3-ref electrode in 5M ZnCl2 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 ZnCl2 electrolyte at a scan rate of 2 mV s−1, the HT-MoO3/C electrode shows a second cycle capacitance of 347.6 F g−1. The higher electrochemical performance of the HT-MoO3/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.

Free‐Standing α‐MoO3/Ti3C2 MXene Hybrid Electrode in Water‐in‐Salt Electrolytes

“…This precursor was hydrothermally treated in 12 mL of water at 220 °C for 24 h. The product of the hydrothermal treatment was filtered and washed with copious amount of water. [41,42] Synthesis of Ti 3 AlC 2 MAX phase, Ti 3 C 2 MXene, and its free-standing film: Ti (99.5%, −325 mesh, Alfa Aesar), Al (99.5%, −325 mesh, Alfa Aesar), and TiC (99.5%, 2 μm, Alfa Aesar) powders were used for MAX phase synthesis. Lithium chloride (LiCl, 99%, Acros Organics), hydrofluoric acid (HF, 48.5-51%, Acros Organics), and hydrochloric acid (HCl, 36.5-38%, Fisher Chemical) were used for the synthesis and delamination of Ti 3 C 2 .…”

“…This precursor was hydrothermally treated in 12 mL of water at 220 °C for 24 h. The product of the hydrothermal treatment was filtered and washed with copious amount of water. [ 41,42 ]…”

Mechanistic understanding of microstructure formation during synthesis of metal oxide/carbon nanocomposites

“…Comparison of these studies 8,12–16 reveals variations in structural properties of the resulting TMO/C materials, especially in terms of nanocomposite microstructure ( i.e. , phase distribution), degree of TMO reduction, and carbon hybridization.…”

“…8,11 Recent works have shown that the carbonization of amine molecules added into the interlayer of layered TMOs can produce TMO/C nanocomposites with a welldispersed carbon phase. 8,[12][13][14][15][16] In some cases, it was described that this synthesis route (and similar ones using different sources of carbon 17 ) yielded heterostructured TMO/C 12,16 (and transition metal dichalcogenide/carbon 18 ) nanocomposites, where layers of dissimilar phases alternate. This particular microstructure results in abundant heterointerfaces which may synergistically combine benecial electrochemical properties of the individual building blocks (redox-activity, electrical conductivity).…”

“…This particular microstructure results in abundant heterointerfaces which may synergistically combine benecial electrochemical properties of the individual building blocks (redox-activity, electrical conductivity). 19,20 Comparison of these studies 8,[12][13][14][15][16] reveals variations in structural properties of the resulting TMO/C materials, especially in terms of nanocomposite microstructure (i.e., phase distribution), degree of TMO reduction, and carbon hybridization. A more generalized understanding of the synthesis process is required to be able to precisely tune the resulting nanocomposite properties.…”