FeNi nanoparticles on Mo₂TiC₂T_x MXene@nickel foam as robust electrocatalysts for overall water splitting

The development of cost-effective electrocatalysts for overall water splitting is highly desirable, remaining a critical challenge at current stage. Herein, a class of composite FeNi@MXene (Mo₂TiC₂T_x)@nickel foam (NF) has been synthesized through introducing Fe²⁺ ions and in-situ combining with surface nickel atoms on nickel foam. The obtained FeNi@Mo₂TiC₂T_x@NF exhibited high activity with overpotentials of 165 and 190 mV for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a current density of 10 mA·cm^-2, respectively. The synergetic effects of Mo₂TiC₂T_x and FeNi nanoalloys lead to increasing catalytic activities, where MXene provides high active surface area and rich active sites for HER, and FeNi nanoalloys promote the OER. Theoretical simulation of electron exchange capacity between FeNi and MXene in FeNi@Mo₂TiC₂T_x catalyst shows that electrons transferred from surface Mo atoms to the interface between FeNi and MXene, indicating that the electrons are accumulated near the FeNi nanoparticles. This kind of electronic distribution facilitates the formation of intermediate of NiOOH. Correspondingly, (H⁺ + e^-) is more inclined onto Mo–Ni interfaces for HER. The Gibbs free energy changes for H* to HER and potential-limiting step for -OOH intermediate in OER over FeNi@Mo₂TiC₂T_x are much less than those on bare MXene. The catalyst can be further used for overall water splitting in alkaline solution, realizing a current density of 50 mA·cm^-2 at 1.74 V. This work provides a facile strategy to achieve efficient and cheap catalysts for new energy production.