MOF-derived molybdenum carbide-copper as an electrocatalyst for the hydrogen evolution reaction

Abstract

We have used molybdenum-copper metal-organic framework (Mo-Cu MOF) as a precursor, and its porous structure as a spatially confined environment to suppress the overgrowth and aggregation of nanoparticles during high-temperature carbonization for synthesis of MOF-derived molybdenum carbide-copper. The Mo-Cu-MOF precursor was carbonized at high temperature under a predefined gas flow condition (nitrogen → 20 % methane/hydrogen mixed gas) and the product was transformed from MoO2-Cu to ŋ-MoC-Cu. Then, by changing the process temperature (800°C → 1000°C), ŋ-MoC-Cu was transformed into β-Mo2C-Cu. The microstructure analysis by transmission electron microscopy (TEM) revealed a gradual change of octahedral structure of MoxC-Cu with the increase of temperature. X-ray diffraction (XRD) analysis identify the phase composition and the grain size of carbide molybdenum inside the MoxC-Cu structure. The carbide molybdenum grain size increased and transformed from ŋ-MoC to β-Mo2C with the increase of the carbonization temperature from 800 °C to 1000 °C. ŋ-MoC-Cu obtained at a carbonization temperature of 800°C showed the best electrochemical performance, with η10 mA = −233 mV and Tafel slope = 73 mV/dec.