GO-based membranes with enhanced stability and permeability by implanting etched-MXene nanosheets: The role of binding energy in stabilizing 2D membranes

Graphene oxide (GO) stands out as a promising choice for the construction of next generation nanofiltration membranes in wastewater purification. Nevertheless, achieving the requisite stability and optimal permeability for effective separation of aqueous molecules and ions poses a formidable challenge for graphene oxide membranes. In this study, a series of GO/etched-MXene membranes with markedly enhanced stability and permeability was fabricated to provide high-level performance. Due to seemly etching process, the optimal GO/etched-MXene membrane featured additional nanochannels for faster mass transfer, consequently evincing a high water permeance of 88.2 ± 3.8 L m−2 h−1 bar−1 with an excellent dye/salt separation efficiency (CR/NaCl selectivity = 22.6, CR/Na2SO4 selectivity = 42.0). Noticeably, the introduction of etched-MXene nanosheets demonstrated a pronounced enhancement in stabilizing the GO membrane within aqueous environment. The density functional theory (DFT) calculations showed that the binding energy of MXene nanosheets (−7.68 eV) was significantly larger than GO nanosheets (−1.11 eV). According to charge difference density results, compared with GO nanosheets, the electrons transfer in MXene nanosheets was more concentrated. As a result, the specially-designed GO/etched-MXene membranes could maintain a stable separation performance during crossflow filtration, while the pristine GO membrane rapidly cracked. This approach is anticipated to establish a theoretical framework for comprehending the contribution of nanosheet binding energy in stabilizing two-dimensional membranes, fostering synergistic advantages in the advancement of GO membranes characterized by both elevated water permeance and requisite stability in water treatment.