Single-Pot Solvothermal Synthesis of Single-Crystalline Nickel–Metal Organic Framework Nanosheets for Direct Iron Fuel Cell Applications

The usage of iron leads to the generation of large quantities of scrap iron, which is hazardous to health and causes environmental pollution. Recycling techniques are expensive and involve high energy consumption. Instead of recycling, scrap iron can be used as an alternative potential source for fuel cell applications. Here, we report the synthesis of a single-crystalline nickel-based MOF (Ni-MOF), via a single-pot solvothermal technique, as an electrocatalyst to produce hydrogen from scrap iron. Detailed characterization reveals the nanosheet morphology of the Ni-MOF obtained by FESEM; at the same time Ni-MOF formation is confirmed through the XRD spectrum. The as-synthesized Ni-MOF is deposited on nickel foam (NF) and used as an electrocatalyst (Ni-MOF/NF) which exhibits a peak current density of 8.8 A/g (scrap) and response toward hydrogen production at an onset potential of 0.5 V (vs Hg/HgO). The improved performance of the Ni-MOF/NF electrode is ascribed to the high catalytic activity of Ni-MOF owing to the multiple oxidation states of Ni (i.e., Ni 2+/3+ ); the reversible transformation between +2 and +3 oxidation states results in the redox peaks of the catalytic reaction; and the organic ligands in the MOF structure help in improving the conductivity and pore size of the material. The Ni-MOF/NF electrode exhibits outstanding stability with ∼88.1 and ∼72.9% capacity retention after 100,000 and 50,000 s for scrap and iron metal powder, respectively. This proves that the theickel metal–organic framework coated on nickel foam (Ni-MOF/NF) electrocatalyst is an outstanding material for iron source-based fuel cell applications.