Abstract:

To tackle the energy crisis and achieve more sustainable development, hydrogen as a clean and renewable energy resource has attracted great interest. Searching for cheap but efficient catalysts for hydrogen production from water splitting is urgently needed. In this report, bimetallic Fe-Mo sulfide/carbon nanocomposites that derived from a polyoxometalate phosphomolybdic acid encapsulated metal-organic framework MIL-100 (PMA@MIL-100) have been generated and their applications in electrocatalytic hydrogen generation were explored. The PMA@MIL-100 precursor is formed via a simple one-pot hydrothermal synthesis method and the bimetallic Fe-Mo sulfide/carbon nanocomposites were obtained by chemical vapor sulfurization of PMA@MIL-100 at high temperatures. The nanocomposite samples were fully characterized by a series of techniques including X-ray diffraction, Fourier-transform infrared analysis, thermogravimetric analysis, N₂ gas sorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and were further investigated as electrocatalysts for hydrogen production from water splitting. The hydrogen production activity of the best performed bimetallic Fe-Mo sulfide/carbon nanocomposite exhibits an overpotential of -0.321 V at 10 mA cm^-2 and a Tafel slope of 62 mV dec^-1 with a 53 % reduction in overpotential compared to Mo-free counterpart composite. This dramatic improvement in catalytic performance of the Fe-Mo sulfide/carbon composite is attributed to the homogeneous distribution of the nanosized iron sulfide, MoS₂ particles, and the formation of Fe-Mo-S phases in the S-doped porous carbon matrix. This work has demonstrated a potential approach to fabricate complex heterogeneous catalytic materials for different applications.

Key words: MOF, Nanocomposite, Encapsulation, Metal sulfide, Hydrogen generation