Hydroxide Conduction Enhancement of Chitosan Membranes by Functionalized MXene

Abstract

In this study, imidazolium brushes tethered by –NH2-containing ligands were grafted onto the surface of a 2D material, MXene, using precipitation polymerization followed by quaternization. Functionalized MXene was embedded into chitosan matrix to prepare a hybrid alkaline anion exchange membrane. Due to high interfacial compatibility, functionalized MXene was homogeneously dispersed in chitosan matrix, generating continuous ion conduction channels and then greatly enhancing OH− conduction property (up to 172%). The ability and mechanism of OH− conduction in the membrane were elaborated based on systematic tests. The mechanical-thermal stability and swelling resistance of the membrane were evidently augmented. Therefore, it is a promising anion exchange membrane for alkaline fuel cell application.

Highly Efficient Nb2C MXene Cathode Catalyst with Uniform O‐Terminated Surface for Lithium–Oxygen Batteries

“…The binding energy at around ≈54.8 eV occurred in Li 1s spectra can be relevant to the Li 2 O 2 discharge product, while the binding energy located at 56.1 eV could be attributed to the accumulation of Li 2− x O 2 products on the electrode surface. [ 44–51 ] The discharge products were mainly Li 2− x O 2 at stage I (Figure 5c), then crystalline Li 2 O 2 formed (Figure 5d) through further growth of discharge products, and the result was basically consistent with the previous ex situ SEM and TEM observation. Notably, the peak area ratio between Li 2− x O 2 /Li 2 O 2 increased at stage III (Figure 5e) compared with that in stage II when recharging at the low voltage platform, indicating the prior delithiation reaction and facile disintegration of products Li 2− x O 2 at the initial of charge process.…”

“…The porous loosely stacked structure which diminishes products size, increases contacting area and tends to amorphization is benefited to the charge and ion transfer, also contributes to the better cycle life at the ultrahigh current density. [ 27–58 ] Similar results were also observed for the FNb 2 C MXene cathode cycled at 2000 and 1000 mA g −1 with fixed capacity of 1000 mAh g −1 (Figure 3g). As shown in Figure S11 in the Supporting Information, film‐like discharge products (Figure S11a, Supporting Information) and loosely stacked nanoflakes with a size range of 50−100 nm and thickness of ≈10 nm (Figure S11b, Supporting Information) formed when discharged to 600 and 1000 mAh g −1 at the current density of 1000 mA g −1 .…”

“…[ 53,54 ] The peak at 208.4 eV representing the CNbFx bonding was not identified in Figure 2g compared to that in Figure S4a in the Supporting Information, indicating the removement of F group after annealing corresponding with the results in survey spectra (Figure 2e). [ 49–55 ] Similarly, the peak at 531.6 eV corresponding to CNb(OH) x bonding before annealing in Figure S4c in the Supporting Information vanished and intensity of CNbO x peak at 531.0 eV greatly increased in the high‐resolution spectrum of O 2s shown in Figure 2i after annealing, indicating the decomposition of anchored OH group during annealing. Based on the XPS results, the final states of Nb on the surface of FNb 2 C MXene were mainly Nb(4+)O, Nb(I, II, IV) (203.8 eV for 3d 5/2 and 206.6 eV for 3d 3/2 , refer to species including CNbO x and H 2 O ads ), and Nb 2 O 5 (207.6 eV for 3d 5/2 and 210.4 eV for 3d 3/2 ).…”

“…After heat treatment, the peaks matched well with C 1s, O 1s, and Nb 3p in the survey pattern as shown in Figure 2e, meanwhile, the peaks belong to F element were not identified despite the existence before heat treatment. In the highresolution XPS spectra of F element (Figure 2f), [49][50][51][52] it can be clearly identified that anchored F group was removed during heat treatment. In the high-resolution XPS spectrum of Nb 3d (Figure 2g), the main peaks located at 206.7 eV (3d 5/2 ) and 209.5 eV (3d 3/2 ) represents the Nb(4+)O bonding.…”

“…[53,54] The peak at 208.4 eV representing the CNbFx bonding was not identified in Figure 2g compared to that in Figure S4a in the Supporting Information, indicating the removement of F group after annealing corresponding with the results in survey spectra (Figure 2e). [49][50][51][52][53][54][55] Similarly, the peak at 531.6 eV corresponding to CNb(OH) x bonding before annealing in ). [53] The NbC component was detected in the high-resolution spectrum of C 1s spectrum (Figure 2h and Figure S4b, Supporting Information), which refers to CNbT x .…”