3D Ni and Co redox-active metal-organic frameworks based on ferrocenyl diphosphinate and 4,4 '-bipyridine ligands as efficient electrocatalysts for the hydrogen evolution reaction

摘要

New 3D Ni and Co redox-active metal-organic frameworks based on ferrocenyl diphosphinate and 4,4 '-bipyridine ligands have been synthesized, characterized by single crystal X-ray diffraction and spectro-scopic techniques and explored as stable electrocatalysts capable of meeting two important parameters: the overpotential and Tafel slope (TS) in the hydrogen evolution reaction (HER). The electrochemical studies suggest that the reaction kinetics of a Ni-MOF (1) catalyst is more favorable than that of a Co-MOF (2) catalyst. Particularly, Ni-MOF exhibits better HER performance with an overpotential of 350 mV at a current density of 10 mA cm(-2), a small TS of 60 mV dec(-1) and superior long-term durability (of up to 10 000 cycles), ranking it among the most active non-noble metal-based molecular electrocatalysts. The introduction of a 4,4'-bpy linker in 2 significantly changes the catalytic properties in an organic or aqueous environment compared to 1D cobalt polymers based on ferrocenyl diphosphinate. For Co-MOF 2, there is a significant decrease in the overvoltage by similar to 440 mV in comparison with the 1D Co polymer in an organic medium and by 50 mV in an aqueous medium. The TS changes from 120 to 65 mV dec(-1) when moving from 1D CofcdHp to a 3D structure of 2. Thus, a 4,4 '-bpy linker reduces the overvoltage and gives more favorable HER kinetics (lower TS). These results provide important guidelines for the rational design of non-precious metal electrocatalysts.