Tuning the morphology and electron structure of metal-organic framework-74 as bifunctional electrocatalyst for OER and HER using bimetallic collaboration strategy

Compared to traditional 3D bulk metal-organic frameworks (MOFs), 2D MOFs are recently considered as an ideal electrocatalyst because they possess several advantages containing nanometer thickness for the efficient mass transport and enlarged surface areas containing more available active metal sites. In this work, the 2D NiFe-MOF-74 nanosheets directly growing on nickel foam (NF) are fabricated by a one-step solvothermal process without using annealing treatment. Remarkably, it is noted that thin layered MOF shape can be obtained by the collaboration of two metals, Ni and Fe which favors in maximum utilization of the active sites. Also, the electron environment of Ni and Fe, together with the conductivity of MOF-74 can be tuned by the cooperative effect of two metals. The optimized NiFe-MOF-74 electrode displays higher activity than that of a metal MOF-74 and the benchmarking catalysts for oxygen evolution reaction (OER), which drives a current density of 10 mA cm−2 at the overpotentials of only 208 mV for OER and 195 mV for hydrogen evolution reaction (HER), respectively. More importantly, the morphology of NiFe-MOF-74 is nearly retained after 5000 cycles CV test for OER. The overall water splitting of as-prepared NiFe-MOF-74 electrode requires 1.58 V to achieve a current density of 10 mA cm−2, making it as a promising bifunctional electrocatalysts for water-splitting system.