Synergistic effect of ceria on the structure and hydrogen evolution activity of nickel nanoparticles grown on reduced graphene oxide
In this study, a facile chemical reduction procedure for the synthesis of nickel nanoparticles on a ceria–reduced graphene oxide (rGO) composite (ceria–rGO) is reported. To optimize the amount of ceria in the composites, various techniques were applied for the characterization and evaluation of the samples. Fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and electrochemical techniques were used to determine the best composition. The results showed the influence of ceria incorporation in the matrix on the size of the prepared nickel nanoparticles (almost 12 nm in the presence of ceria and 24 nm in the absence of ceria). The prepared composites were used as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media. The results show an excellent catalytic activity of Ni/ceria–rGO (1,1) with an onset overpotential of −15 mV (vs. RHE). Also, the obtained Tafel slope of this sample was 107.3 mV dec−1, which is lower than the reported value for nickel in alkaline media (120 mV dec−1). Finally, the effect of incorporating ceria into Ni/ceria–rGO on the HER activity and electrochemical impedance spectroscopy response of the samples are discussed comprehensively.