Three-dimensional macroporous NiCo₂O₄ sheets as a non-noble catalyst for efficient oxygen reduction reactions

A facile and low-cost strategy is developed to prepare three-dimensional (3D) macroporous NiCo₂O₄ sheets, which can be used as a highly efficient non-noble metal electrocata-lyst for the oxygen reduction reaction (ORR) in alkaline conditions. The as-obtained sheets have a thickness of about 150 nm and feature a typical 3D macroporous structure with pore volumes of up to 0.23 cm³g^-1, which could decrease the mass transport resistance and allow easier access of the reactants to the active surface sites. The as-prepared macroporous NiCo₂O₄ sheets exhibit high electrocatalytic activity for ORR with a four-electron pathway, good long-term stability and high tolerance against methanol. The unique 3D macroporous structure and intrinsic properties may be responsible for their high performance.