Fig. 1: TFN-CEM with high and uniform loading of N-LTO.

A Schematic illustration of N-LTO synthesis and N-LTO-PA layer formation. In the schematic of the N-LTO-PA layer, the pink area with scattered yellow dots represents the PA network consisting of MPD and TMC. B SEM images of LTO (B1) and N-LTO nanoparticles (B2). C XRD spectra of LTO and N-LTO nanoparticles; peaks that match the standard Li₂TiO₃ XRD pattern from the Joint Committee on Powder Diffraction Standards (JCPDS) #33-0831 are marked by triangles. D FTIR spectra of LTO and N-LTO nanoparticles. The insert shows the anticipated surface chemistry of N-LTO. The peaks shared by LTO and N-LTO nanoparticles are marked by colored bars. Unique peaks that appeared in N-LTO are marked by arrows. E Photos of the N-LTO-PA side (E1) and the CEP side (E2) of the membrane prepared with 0.5 g L⁻¹ N-LTO (N-LTO-PA-0.5). F Cross-sectional SEM image of the N-LTO-PA-0.5 membrane showing a TFN structure consisting of CEP, PSf and N-LTO-PA layers. The N-LTO-PA layer is too thin to be observed clearly at the top of the PSf layer at this scale, but the surface clearly exhibits characteristic features of the N-LTO-PA layer. G SEM image of the N-LTO-PA layer surface of the N-LTO-PA-0.5 membrane. H Surface SEM images of the commercial CEM (COMM), lab-made PA membrane (PA), unmodified LTO incorpated PA membrnae (LTO-PA), and a membrane formed by reacting N-LTO only with TMC without MPD on the PSf surface (N-LTO-TMC) I Cross-sectional TEM image of the N-LTO-PA-0.5 layer formed on the PSf layer. The bright areas are LTO nanoparticles. J XPS spectra of the N-LTO-PA-0.5 membrane. The insert shows the C1s spectrum.