Flower-like Layered NiCu-LDH/MXene Nanocomposites as an Anodic Material for Electrocatalytic Oxidation of Methanol

Abstract

Direct methanol fuel cell (DMFC) technology has grabbed much attention from researchers worldwide in the realm of green and renewable energy-generating technologies. Practical applications of DMFCs are marked by the development of highly active, efficient, economical, and long-lasting anode catalysts. Layered double hydroxide (LDH) nanohybrids are found to be efficient electrode materials for methanol oxidation. In this study, we synthesized NiCu-LDH/MXene nanocomposites (NCMs) and investigated their electrochemical performance for methanol oxidation. The formation of NCM was verified through field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET), and X-ray photoemission spectroscopy (XPS) analyses. The cyclic voltammetry, chronoamperometry, and electron impedance spectroscopy techniques were carried out to assess the electrocatalytic ability of the methanol oxidation reaction. The incorporation of MXene enhanced the methanol oxidation 2-fold times higher than NiCu-LDH. NCM-45 exhibited high peak current density (86.9 mA cm–2), enhanced electrochemical active surface area (7.625 cm2), and long-term stability (77.8% retention after 500 cycles). The superior performance of NCM can be attributed to the synergistic effect between Ni and Cu and, further, the electronic coupling between LDH and MXene. Based on the results, NCM nanocomposite is an efficient anodic material for the electrocatalytic oxidation of methanol. This study will open the door for the development of various LDH/MXene nanocomposite electrode materials for the application of direct methanol fuel cells.

β-Cyclodextrin-Stabilized CuO/MXene Nanocomposite as an Electrode Material for High-Performance Supercapacitors

“…Moreover, three plausible contributions were obtained from the O 1s spectrum of CuO@βCD corresponding to C–O (532 eV), surface hydroxyl groups (−OH, 533.30 eV), and the peak attained at the binding energy of 535.1 eV (O 1s) signifying O 2– ions that are bonded to the Cu 2+ ions of CuO@βCD; these peaks were successfully identified from Figure S7c . Ti 2p profiles (Figure c) reveal that the potential contributions of CuO@βCD/MXene (1:1) composites are Ti 2p 3/2 (454.85 eV), Ti–C (455.85 eV), Ti 2+ (456.75 eV), Ti–C–F (457.75 eV), Ti 2 O 3 (458.95 eV), Ti 2p 1/2 (460.65 eV), Ti–O (461.95 eV), and Ti 4+ (464.25 eV) …”

“…The high-resolution C 1s spectra of the CuO@βCD/MXene (1:1) composite and CuO@βCD are deconvoluted into different functional groups of carbon (Figure a and Figure S7b). In Figure a, the C 1s XPS spectrum of the CuO@βCD/MXene (1:1) composite was deconvoluted into six peaks at the binding energies of 281.12, 283.27, 284.50, 285.87, 287.04, and 288.46 eV that correspond to Ti–C, sp 2 C–C, C–H/sp 3 C–C, C–OH, C–O, and C–F bonds, respectively. , Furthermore, the high-resolution C 1s spectrum of CuO@βCD shown in Figure S7b was deconvoluted into three peaks at binding energies of 284.50, 285.73, and 287.84 eV, which correspond to C–H/sp 3 C–C, C–OH, and C–O, respectively. In the case of the O 1s spectrum of the CuO@βCD/MXene (1:1) composite (Figure b), it was deconvoluted into four peaks related to Ti–O (530.0 eV), C–O (532 eV), surface hydroxyl groups (−OH, 533.30 eV), and O 2– ions that are bonded to the Cu 2+ ions (535.1 eV, O 1s).…”

“…The specific capacitance of CuO@βCD is determined to be 384.60, 464.85, 473.07, 490.08, 510.68, and 581.68 F g –1 , for MXene is 380.23, 567.44, 622.13, 710.84, 812.78, and 1125.21 F g –1 , for CuO@βCD/MXene (1:1) is 867.36, 1134.25, 1199.37, 1263.19, 1386.54, and 1693.43 F g –1 , for CuO@βCD/MXene (4:1) is 301.30, 436.03, 459.64, 495.89, 544.76, and 625.67 F g –1 , and for CuO@βCD/MXene (1:4) is 5.61, 21.67, 26.56, 33.54, 43.38, and 56.61 F g –1 at 9.09, 4.54, 3.63, 2.72, 1.81, and 0.90 A g –1 , respectively. Thus, an increase in the MXene concentration may reduce the amount of active CuO@βCD material and cause aggregation of MXene nanosheets that hinder electrolyte transportation, therefore affecting the overall performance of the CuO@βCD/MXene (1:4) nanocomposite electrode. , …”

“…61 Ti 2p profiles (Figure 6c) reveal that the potential contributions of CuO@βCD/MXene (1:1) composites are Ti 2p 3/2 (454.85 eV), Ti−C (455.85 eV), Ti 2+ (456.75 eV), Ti−C−F (457.75 eV), Ti 2 O 3 (458.95 eV), Ti 2p 1/2 (460.65 eV), Ti−O (461.95 eV), and Ti 4+ (464.25 eV). 59 Further, Figure S7d illustrates the Cu 2p spectrum of CuO@ βCD, and the subsequent two peaks detected at the binding energies of 934.45 and 954.65 eV can be attributed to Cu 2p 3/2 and Cu 2p 1/2 , respectively. As shown in Figure S7d, the shakeup subpeaks at 934.45 and 936.55 eV were allocated to CuO and Cu(OH) 2 , respectively.…”

“…This analysis suggests that Cu is in a +2 oxidation state and is consistent with the earlier reports. 59,63 Figure 6d demonstrates the Cu 2p deconvoluted XPS core spectra of the CuO@βCD/MXene (1:1) composites. The two peaks seen at the binding energies of 934.78 and 954.36 eV can be attributed to Cu 2p 3/2 and Cu 2p 1/2 , respectively.…”