Harvesting osmotic energy from proton gradients enabled by two-dimensional Ti3C2Tx MXene membranes

Osmotic energy is a kind of blue energy that has recently been identified as an additional source of clean energy. Using a membrane-based reverse electrodialysis (RED) process, this blue energy can be obtained from acidic industrial wastewater with different proton concentration gradients. However, this process demands highperformance membrane that can withstand harsh environments, possessing the advantages of wide pH tolerance, high-temperature resistance and chemical stability, developing such membranes remain a challenge. Herein, we report a two-dimensional (2D) lamellar Ti3C2Tx MXene membrane-based RED device for osmotic energy capturing from proton gradients. Such a membrane exhibits a typical surface-charge-governed ion transport feature. Moreover, the MXene membrane-based energy harvesting device holds the merits of outstanding pH and temperature resistance. It exhibits an output power density of 6.5 W/m2 and also demonstrates stability over 200 h at pH 1/4 0, which is 30% higher than the commercialization benchmark (5 W/m2). The osmotic power density can be further enhanced to 11.1 W/m2 at 330 K, demonstrating excellent thermal and chemical stability. This work can help better understand protons' transport behaviors in MXene membranes and open new avenues for applications in sustainable power conversion and wastewater treatment.