A novel "butter-sandwich" Ti3C2Tx/PANI/PPY electrode with enhanced adsorption capacity and recyclability toward asymmetric capacitive deionization.

• A novel 'butter-sandwich' electrode was invented for capacitive deionization. • The salt adsorption capacity achieved to 39.62 mg g−1. • After 30 times cycles, the salt adsorption capacity remained at almost 100%. Capacitive deionization (CDI) is an environmentally-friendly-water-treatment technology, whereas its wide application has been limited by the low salt adsorption capacity and poor recyclability of electrode materials. In this study, a novel Ti 3 C 2 T x /PANI/PPY electrode is invented with a "butter-sandwich" microstructure, where bread-like Ti 3 C 2 T x slices are intercalated by polypyrrole (PPY) spheres, and then glued by butter-like polyaniline (PANI). Thus, the negatively charged PPY is fastened inside Ti 3 C 2 T x slices by positively charged PANI for a superhigh structural stability and elevated specific surface area. When Ti 3 C 2 T x /PANI/PPY is used as the electrode for CDI, a high salt adsorption capacity (39.62 mg g−1), a fast salt adsorption rate (2.64 mg g−1 min−1) and a high cycling stability of almost 100% for 30 times are obtained, surpassing those of the Ti 3 C 2 T x electrodes and many other related materials in literature. Such an outstanding CDI performance can be ascribed to the intercalation of PPY, which enlarges the layer spacing of Ti 3 C 2 T x as well as the ion storage space, and the binding of them by PANI, which provides more paths for electron transport and improves the ion adsorption rate. This work provides a new direction to enhance the performance of capacitive deionization by an attentive "butter-sandwich" new microstructural design strategy. [ABSTRACT FROM AUTHOR]