Nitrogen-Doped Titanium Carbide (Ti 3 C 2 T x ) MXene Nanosheet Stack For Long-Term Stability and Efficacy in Au and Ag Recovery.

The development of efficient adsorbents for the practical recovery of precious metals from electronic waste is vital to advanced energy/environment industries. Ti 3 C 2 T x MXene-based materials are promising adsorbents for aqueous environments; however, the highly defective and super hydrophilic nature of the MXene surface hinders its practical applications. Here, we report that nitrogen-doped MXene (N-MXene) nanosheet stacks, prepared via high-energy planetary ball milling under N 2 purging, exhibited a long-term stable and excellent recovery capability for Au and Ag ions via the nitrogenation of defective vacancies. Notably, these microscale nanosheets could facilitate the sustainable production of Au and Ag from secondary sources, exhibiting a high recovery rate and capability (1198 mg g -1 for Au and 1528 mg g -1 for Ag), long-term stable storability (21 d), and high selectivity (K d of 1.67 × 10 6 for Au and 2.07 × 10 7 for Ag). Furthermore, the reversible redox chemistry of N-MXene facilitated its repeated use in adsorption/desorption cycles.