Two-Dimensional Co@N-Carbon Nanocomposites Facilely Derived from Metal-Organic Framework Nanosheets for Efficient Bifunctional Electrocatalysis

Metal-organic frameworks (MOFs) and MOF-derived nanomaterials have recently attracted great interest as highly efficient, non-noble-metal catalysts. In particular, two-dimensional MOF nanosheet materials possess the advantages of both 2D layered nanomaterials and MOFs and are considered to be promising nanomaterials. Herein, we report a facile and scalable in situ hydrothermal synthesis of Co-hypoxanthine (HPA) MOF nanosheets, which were then directly carbonized to prepare uniform Co@N-Carbon nanosheets for efficient bifunctional electrocatalytic hydrogen-evolution reactions (HERs) and oxygen-evolution reactions (OERs). The Co embedded in N-doped carbon shows excellent and stable catalytic performance for bifunctional electrocatalytic OERs and HERs. For OERs, the overpotential of Co@N-Carbon at 10mAcm(-2) was 400mV (vs. reversible hydrogen electrode, RHE). The current density of Co@N-Carbon reached 100mAcm(-2) at an overpotential of 560mV, which showed much better performance than RuO2; the largest current density of RuO2 that could be reached was only 44mAcm(-2). The Tafel slope of Co@N-Carbon was 61mVdec(-1), which is comparable to that of commercial RuO2 (58mVdec(-1)). The excellent electrocatalytic properties can be attributed to the nanosheet structure and well-dispersed carbon-encapsulated Co, CoN nanoparticles, and N-dopant sites, which provided high conductivity and a large number of accessible active sites. The results highlight the great potential of utilizing MOF nanosheet materials as promising templates for the preparation of 2D Co@N-Carbon materials for electrocatalysis and will pave the way to the development of more efficient 2D nanomaterials for various catalytic applications.