Magnetron Sputtering Deposition Cu@Onion-like N-C as High-Performance Electrocatalysts for Oxygen Reduction Reaction.

The idea of a core-shell structure can promote the utilization of nonprecious metallic catalysts by enhancing their activity and stability for the oxygen reduction reaction (ORR). Developing a low-cost, high-efficiency, and high-reproducibility method for synthesizing core-shell-structured materials represents an urgent challenge. Here, we fabricate encapsulated Cu nanoparticles with nitrogen-doped onion-like graphite nanoshells (Cu@onion-like N-C) as an efficient ORR catalyst by magnetron sputtering, in which the graphite shells grow by an in situ self-assembly process activated by the surface-catalyzed behavior with Cu nanoparticles. The results show that the CuCN-650 °C catalyst achieves the optimized Cu@onion-like N-C structure with small-sized Cu nanoparticles and a few-layer nanoshells and exhibits excellent ORR electrocatalytic properties, including a half-wave potential and onset potential similar to those of commercial Pt/C, coupled with better stability and higher methanol tolerance than for commercial Pt/C in alkaline electrolytes. The internal Cu nanoparticles in the core-shell structure not only promote the formation of a high content of pyridinic N but also donate the electronic charges to outer N-doped C shells, and thus the synergistic effect between the encapsulated Cu nanoparticles and N-doped C shells is responsible for the excellent electrocatalytic activity for the ORR.