Enhanced hydrogen storage performance of magnesium hydride with incompletely etched Ti3C2Tx: The nonnegligible role of Al

The pronounced enhancement on the hydrogen storage performance of MgH2 has been achieved by completely etched MXenes. However, whether the completely removal of Al is necessary and what role the residual Al can play are still unresolved issues. Herein, for the first time, Ti3C2Tx MXenes with different residual Al are prepared to improve the hydrogen storage performance of MgH2. The result shows that the proper residual Al for incompletely etched Ti3C2Tx has a very important responsibility for the improvement of catalytic activity. Different with metallic Al and other Al-containing additives, the unique Ti-Al metallic bonds assisted by surface functional group (-O) can change the electronic structure of Al, which not only hinder the formation of Mg-Al alloys, but also assist the escape of H atoms from MgH2 and enhance the absorption of H atom on catalyst. Meanwhile, the de/hydrogenation process of MgH2 can further be enhanced by multivalent Ti. This report will arouse attention for incompletely etched MXenes and provide a new strategy to optimize properties of MXenes in various fields.