Fabrication of interface-engineered Ni/NiO/rGO nanobush for highly efficient and durable oxygen reduction

Developing non-noble metal electrocatalytic cathode materials with high catalytic activity, low cost and good durability is crucial for fuel cell applications on a large scale. Herein, we presented a novel Ni/NiO/rGO nanobush by controlled hydrolysis, anchoring nucleation and microwave-assisted hydrothermal process, as a highly effective cathode catalyst material for oxygen reduction reactions in an alkaline medium. The as-prepared Ni/NiO/rGO nanobush not only had abundant interface structures that can promote electron transfer but also maximized the exposure of active sites. The effects of complexing agent and precipitant on the interrelated hierarchical structure, the function of the composite interfaces and the oxygen reduction reaction (ORR) performance of the composite catalyst were subsequently investigated in detail. As a novel non-noble metal ORR electrocatalyst, Ni/NiO/rGO nanobush, of which the half-wave potential was 0.812 V, presented excellent catalytic efficiency in an alkaline solution with an electron transfer number of 3.92. After reacting for 20000 s, the retention rate of its current density still reached 87.9% and the current density was only lost by 9% after reacting for 1000s through the anti-methanol poisoning test. Thus, the long-term stability and methanol tolerance are superior to that of commercial Pt/C catalysts. This study provides a new structural engineering strategy for the non-noble metal ORR electrocatalyst composite.