Unraveling the potential of MoTiCT MXene nanosheets in hierarchical heterostructures for enhancing electrocatalytic overall water splitting and urea electrolysis.

The rational design of economical and highly active multifunctional electrocatalysts is urgently needed for producing sustainable hydrogen. Here, we introduce a novel heterostructured electrocatalyst (NFM) by integrating NiCoO and FeCoS with MoTiCT-MXene nanosheets on a nickel foam substrate for the robust electrocatalytic water splitting and urea oxidation. Notably, the optimized NFM electrocatalyst achieves an impressive activity, requiring ultra-low overpotentials of 58.2, 190.3 mV for the hydrogen evolution reaction (HER) and 182.4, 241.5 mV for the oxygen evolution reaction (OER) to reach current rates of 10 and 100 mA cm, respectively, in 1 M KOH. When utilized as both the anode and cathode in a full water electrolyzer, NFM achieves a cell voltage of only 1.52 V at 10 mA cm and exhibits long-term durability over 100 h at 100 mA cm, outperforming many conventional electrolyzer systems. Finally, in the context of urea electrolysis, the NFM catalyst operates at a low potential of 1.40 V to achieve 100 mA cm, showcasing its multifunctional capabilities. Density functional theory calculations verify that the rich heterointerfaces within the NFM catalyst facilitates interfacial electron transport, leading to an enhancement in intermediate adsorption and reducing the energy barrier for the HER/OER. More importantly, the synergistic interaction at these nanointerfaces modulates electron density around the active sites, unlocking its potential for use in high-performance electrocatalytic applications.