N‐Doping Fe‐C@Nb2CTx MXenes with High Stability and Strong Activity for Sodium‐Ion Storage and Overall Water Splitting

Abstract The development of highly stable and strongly active electrode materials for sodium‐ion batteries (SIBs) and overall water splitting (OWS) is critical in sustainable energy storage and conversion systems. Here, a new electrode material N‐Fe‐C@Nb 2 CT x is introduced, with a layered sandwich structure consisting of N‐doping Fe‐MOF derived‐nanorods (Fe‐C) and Nb 2 CT x MXenes. Specifically, Nb 2 CT x obtained by etching Nb 2 AlC with HF acid is used as the main body to construct the layered sandwich structure with Fe‐C as the filler. Benefiting from this structure, Fe‐MOF grows in situ within Nb 2 CT x , which restrains MXenes aggregation and stacking and also alleviates the bulk effect of sodium‐ion embedding/de‐embedding, thus improving its stability. Again, the more exposed active sites from the layered sandwich structure and N‐doping introduction ensure high reactivity as electrode materials. In addition, Fe‐C nanorods strengthen the linkage between the Nb 2 CT x layers and N‐doping enhances the ion/electron transport rate, thereby boosting the effective mass transfer and electrical conductivity. Density functional theory (DFT) calculations show that Fe‐C and N‐doping help increase the density of states (DOS) and material electrical conductivity. Meanwhile, the generated oxygen species (*OH and *O) in OER are captured by in situ FT‐IR test. As a result, the N‐Fe‐C@Nb 2 CT x electrochemical test displays good electrochemical performance in SIBs and OWS.