Toward explicit anion transport nanochannels for osmotic power energy using positive charged MXene membrane via amination strategy

The reverse electrodialysis (RED) is a potential technique to harvest osmotic energy caused by different salinities. Owing to the negative surface-charged controlling effects of nanofluidic channel in 2D membrane, the power density has been achieved with high energy conversion efficiency for cations (Na+ with the counterpart of Cl−). However, anion-selective nanofluidic channel is rare but still required for promising application of RED due to its high higher diffusion rate resulting in desirable osmotic power energy. In this work, we constructed a two-dimensional layered MXene membrane with positive charge via amination strategy of 3-aminopropyltriethoxysilane (APTES) toward anion selectivity for efficient osmotic power harvesting. The power density of the resultant membrane can achieve a maximum of 10.98 W m−2 at a natural salinity gradient, higher than the commercial benchmark of 5 W m−2. Under regulating environmental conditions including operation temperatures, pH and the existence of pollutants (heavy metal ions and organic pollution) of the simulated electrolyte solution, a higher power density of 20.66 W m−2 can be reached through Cl− transmembrane transport. During 10-h testing, the attenuation of output power density was just 3%. The applicable stability still maintains under the contaminative environment of heavy metal ions or organic pollution. These results will bring an innovative design of anion-selective membrane for osmotic energy conversion and widen the practical application in ion selectivity.