| Summary: | Precious metal-free NiMoM (M = Pr<sub>2</sub>O<sub>3</sub>, Cu<sub>2</sub>O) catalysts have been synthesized through a simple coreduction method, without any surfactant or support material, and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The resultant Pr<sub>2</sub>O<sub>3</sub>- or Cu<sub>2</sub>O-modified NiMo catalysts exhibit different structures, which is due to a difference in the synergistic effects of NiMo and the modifying elements. NiMoPr<sub>2</sub>O<sub>3</sub> has an amorphous structure, with low crystallinity and uniform particle dispersion, while NiMo@Cu<sub>2</sub>O adopts the core−shell structure, where the core and shell are synergistic with each other to promote electron transfer efficiency. The support material-free nanocatalysts Ni<sub>9</sub>Mo<sub>1</sub>(Pr<sub>2</sub>O<sub>3</sub>)<sub>0.375</sub> and Ni<sub>4</sub>Mo@Cu<sub>2</sub>O are both highly efficient compared with bimetallic NiMo catalysts, in terms of hydrogen generation from hydrous hydrazine (N<sub>2</sub>H<sub>4</sub>·H<sub>2</sub>O) at 343 K, with total turnover frequencies (TOFs) of 62 h<sup>−1</sup> and 71.4 h<sup>−1</sup>, respectively. Their corresponding activation energies (Ea) were determined to be 43.24 kJ mol<sup>−1</sup> and 46.47 kJ mol<sup>−1</sup>, respectively. This is the first report on the use of Pr-modified NiMo and core−shell NiMo@Cu<sub>2</sub>O catalysts, and these results may be used to promote the effective application of noble metal-free nanocatalysts for hydrogen production from hydrous hydrazine.
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