In-situ preparation of three-dimensional Ni@graphene-Cu composites for ultrafast reduction of Cr(VI) at room temperature

•The growth of Cu NPs was accomplished by one-step calcination at 560 °C.•The graphene acted as reductant to obtain the conversion of CuO to Cu NPs.•Ni@GE-Cu showed excellent catalytic activity for the reduction of Cr(VI).•The magnetically separable Ni@GE-Cu was very cheap, scalable and recyclable.

Novel three-dimensional Ni@graphene-Cu composites were synthesized by a facile calcination method for the first time. The in-situ generated graphene played an important role in the successful fabrication of Ni@graphene-Cu that it acted both as an effective reductant to achieve the conversion of CuO to Cu nanoparticles (NPs) and as an ideal support to prevent the agglomeration of Cu NPs. The as-prepared Ni@graphene-Cu showed excellent catalytic activity for Cr(VI) reduction to Cr(III) at room temperature with formic acid as reductants.

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