From Ni(OH)2/Graphene composite to Ni@Graphene core-shell: A self-catalyzed epitaxial growth and enhanced activity for nitrophenol reduction

Two-dimensional reduced graphene oxides (RGO) decorated with well-dispersed Ni nanoparticles were facilely fabricated via low temperature annealing of Ni(OH)2/Graphene composites in flowing H2. Ni@Graphene core-shell nanostructures were obtained following a self-catalyzed growth mechanism. The kinetic epitaxial growth of RGO layers on Ni(111) facets originates from annealing-driving phase transition from NiO to Ni at temperature ≥ 450 °C, which was revealed by utilizing comprehensive characterizations including X-ray diffraction, X-ray photoelectron spectroscopy, as well as aberration-corrected scanning transmission electron microscopy. This distinct core-shell structure shows extraordinary catalytic activity in reduction of 4-nitrophenol with the efficiency reaching up to 45.0 L g−1 min−1 at room temperature. Atom-resolved microscopy evidences disclose that such outstanding catalytic activity could be attributed to the synergetic cooperation between Ni phase and epitaxial graphene shell. This work provides general inspiration on the facile fabrication of highly active and non-noble metal-graphene catalysts.

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