Fluorine-doped Mo-Ni-F/NF bifunctional electrode for efficient electrochemical hydrogen storage via quinoxaline

The implementation of liquid organic hydrogen carriers (LOHCs) is constrained by the high energy consumption and strong dependence on precious‑metal catalysts in conventional thermal processes. This work develops a fluorine-doped Mo-Ni-F/NF bifunctional electrode through a simple electrochemical deposition-sintering method for efficient electrochemical hydrogen storage using quinoxaline under ambient conditions. XRD and TEM characterization revealed a unique structure comprising a MoNi₄ shell with embedded Ni nanoparticles, while SEM and EDS mapping confirmed uniform fluoride distribution and enhanced surface morphology. XPS analysis indicated that fluoride modification improved surface characteristics without altering chemical states. The catalyst demonstrates exceptional performance in reversible quinoxaline hydrogenation (92.1 % conversion after 5 h, 95.6 % FE) and dehydrogenation (100 % conversion after 4 h, 97.2 % FE). DFT calculations showed that electron transfer between MoNi₄ and nickel nanoparticles enhanced catalytic activity, while fluorine modulation reduced the adsorption energy of quinoxaline on nickel (111) from −2.84 eV to −0.55 eV, and tetrahydroquinoxaline from −2.08 eV to −0.84 eV, mitigating catalyst poisoning. In situ Raman spectroscopy identified dynamically formed NiOOH as the active phase, which facilitates proton-coupled dehydrogenation via -OH/μ-O-Ni intermediates. This work provides novel catalytic materials and mechanistic insights for the development of low-cost, room-temperature, and highly effective electrochemical LOHC systems.