Synthesis and characterization of C/Cu core–shell particles by hydrogen-free spray pyrolysis assisted with citric acid and sucrose

C/Cu core–shell particles were synthesized by hydrogen-free spray pyrolysis. In order to obtain pure metallic Cu particles having a thin carbon layer, the idea of this study was to use organic additives (citric acid and sucrose) which can act as a reducing agent and carbon source. The crystal phase and the microstructure of C/Cu particles were investigated by changing the content of the organic additives and the pyrolysis temperature. When no organic additive was used, the formation of CuO was inevitable in the hydrogen-free spray pyrolysis. Conversely, a pure Cu metal phase was obtained by adding citric acid or sucrose to the precursor solution. It was found that using both citric acid and sucrose makes it possible to synthesize a C/Cu powder having a complete core–shell structure. Finally, the optimal molar ratio of citric acid and sucrose with respect to the Cu metal was found to be 0.1 and 0.2, respectively. The thickness of the carbon layer could be controlled simply by varying the synthesis temperature from 800 °C to 1100 °C.