The continuous energy-harvesting in moisture environment is attractive for the development of clean energy source. Controlling the transport of ionized mobile charge in intelligent nanoporous membrane systems is a promising strategy to develop the moisture-enabled electric generator. However, existing designs still suffer from low output power density. Moreover, these devices can only produce short-term (mostly a few seconds or a few hours, rarely for a few days) voltage and current output in the ambient environment. Here, we show an ionic diode–type hybrid membrane capable of continuously generating energy in the ambient environment. The built-in electric field of the nanofluidic diode-type PN junction helps the selective ions separation and the steady-state one-way ion charge transfer. This directional ion migration is further converted to electron transportation at the surface of electrodes via oxidation-reduction reaction and charge adsorption, thus resulting in a continuous voltage and current with high energy conversion efficiency.

Nb₂CT_x is an important member of MXene family. It has attracted widespread attention because of its abundant functional groups, high hydrophilicity, high electrical conductivity as well as low ion transport barrier, showing great potential in various applications. In order to utilize the advantages of Nb₂CT_x MXene, the progress of preparation, properties and applications are reviewed in this work. This work focuses on different methods of Nb₂CT_x preparation and applications in electrochemical energy storage (supercapacitors and secondary batteries), electrocatalytic hydrogen evolution, photocatalytic hydrogen evolution, sensors, etc. Additionally, the main problems of self-stacking and prospect of Nb₂CT_x MXene are discussed.