One step molten salt synthesis of nickel nanoparticles incorporated on graphene sheets as non-precious and an effective electrocatalyst for methanol oxidation

Fabricating electrocatalysts based on metal nanoparticles (NPs)/carbon nanomaterials by a facile and cost-effective method have attracted serious attention in the past several years to expand their applications. This study aimed to prepare an effective electrocatalyst based on nickel nanoparticles decorated graphene sheets (NiNPs@Gr) by molten salt synthesis method and to clarify its advantages compared to the calcination method without molten salt. The microscopic characterization revealed that the calcination of nickel/carbon precursors in the molten salt medium resulted in nickel NPs supported on graphene sheets, whereas produce NPs with larger sizes supported on porous carbon without molten salt. X-ray diffraction analysis showed that the catalysts prepared by the molten salt method (NiNPs@Gr-S1 and NiNPs@Gr-S2) resulted in nickel NPs with a mixture of crystalline structures (face-centered cubic and hexagonal close-packed). The electrocatalytic activity of NiNPs@Gr-S1 and NiNPs@Gr-S2 toward methanol oxidation was higher than that of the NiNPs@C catalyst prepared without molten salt. The maximum peak current density of NiNPs@C, NiNPs @Gr-S1, and NiNPs @Gr-S2 are 30, 80, and 81.5 mA/cm2, respectively. Moreover, electrocatalysts derived from molten salt synthesis demonstrated significantly increased electrocatalytic stability. These results emphasize the synthesis of graphene nanosheet-supported Ni NPs in a single step without any additional chemicals, which makes such a strategy promising in trust acquisition for investors in large-scale production of NiNPs@Gr.