Ni/reduced graphene oxide nanocomposite as a magnetically recoverable catalyst with near infrared photothermally enhanced activity

•Nickel nanoparticles/reduced graphene oxide (Ni/rGO) composite has been synthesized.•Ni/rGO can be used as a magnetic recoverable catalyst.•Ni/rGO exhibits good catalytic activity for the reduction of 4-nitrophenol.•The use of rGO as the catalyst support leads to a synergistic effect.•NIR irradiation can enhance the activity of Ni/rGO via photothermal conversion.

A nanocomposite of nickel nanoparticles/reduced graphene oxide (Ni/rGO) has been developed as a magnetic recoverable catalyst with near-infrared (NIR) photothermally enhanced activity owing to the magnetic and catalytic properties of Ni nanoparticles as well as the large specific surface area and excellent NIR photothermal conversion property of rGO. By the hydrazine reduction in ethylene glycol, Ni ions, and graphene oxide were reduced simultaneously to form the Ni/rGO nanocomposite. The resulting Ni/rGO nanocomposite with about 62 wt.% of Ni nanoparticles was nearly superparamagnetic and possessed good catalytic activity toward the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with sodium borohydride. The corresponding pseudo-first-order rate constants increased with increasing the temperature and 4-NP concentration, revealing activation energy of 43.7 kJ/mol and the synergistic effect of rGO. Furthermore, under NIR irradiation, it was demonstrated that the Ni/rGO could efficiently enhance the reduction rate via the photothermal conversion which might induce the heating of local environment around the Ni nanoparticles and reaction medium. Such a nanocomposite was expected to be helpful in the development of NIR or solar photothermally enhanced catalytic systems.

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