Zn-induced defect engineering to activate bimetallic NiCo alloy@nitrogen-doped graphene hybrid nanomaterials for enhanced oxygen reduction reaction

Developing valid strategies to fabricate highly active non-platinum-group metal electrocatalysts for catalyzing the sluggish cathode oxygen reduction reaction (ORR) is urgently required. To our knowledge, the catalytic performance of heterogeneous catalysts is highly related to their electronic and architectural properties. Defect or vacancy engineering is a particularly attractive means of modifying the physicochemical properties of nanomaterials. Herein, in this work, we proposed a facile Zn-induced defect strategy to engineer the electronic and surface structure of non-noble bimetallic NiCo alloy@nitrogen-doped graphene hybrid nanomaterials for boosting ORR activity. The optimized sample shows prominently enhanced activity for the ORR in KOH solution and exhibits better stability and methanol tolerance compared to Pt/C. Physicochemical and electrochemical measurements demonstrate that the enhanced ORR performance is mainly ascribed to the proper Zn-induced vacancy defects, which finely modulate the energy level of electrocatalyst, thus activating ORR process thermodynamically. Moreover, rich exposed active sites from vacancy defects largely facilitate the sluggish kinetics. This strategy is exceptionally promising to be applied to optimize other non-noble metal-based nanomaterials for highly efficient electrocatalysis.