In Situ Grown Bimetallic MOF-Based Composite as Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting with Ultrastability at High Current Densities

A newly designed water-stable NH2-MIL-88B(Fe2Ni)-metal-organic framework (MOF), in situ grown on the surface of a highly conducting 3D macroporous nickel foam (NF), termed NFN-MOF/NF, is demonstrated to be a highly efficient bifunctional electrocatalyst for overall water splitting with ultrastability at high current densities. The NFN-MOF/NF achieves ultralow overpotentials of 240 and 87 mV at current density of 10 mA cm(-2) for the oxygen evolution reaction and hydrogen evolution reaction, respectively, in 1 m KOH. For the overall water splitting, it requires only an ultralow cell voltage of 1.56 V to reach the current density of 10 mA cm(-2), outperforming the pairing of Pt/C on NF as the cathode and IrO2 on NF as the anode at the same catalyst loading. The stability of the NFN-MOF/NF catalyst is also outstanding, exhibiting only a minor chronopotentiometric decay of 7.8% at 500 mA cm(-2) after 30 h. The success of the present NFN-MOF/NF catalyst is attributed to the abundant active centers, the bimetallic clusters {Fe2Ni(mu(3)-O)(COO)(6)(H2O)(3)},in the MOF, the positive coupling effect between Ni and Fe metal ions in the MOF, and synergistic effect between the MOF and NF.