Amine-Functionalized Graphene-Rich NiFe Layered Double Hydroxide Nanostructure for Enhanced Electrocatalytic Water and Urea Oxidation

Development of green technologies for hydrogen generation is crucial but is hindered by the sluggish oxygen evolution reaction (OER). A nickel–iron metal-based layered double hydroxide (NiFe-LDH) has emerged as an efficient material as an OER catalyst, but the standalone material is lacking due to its poor conductivity and a sluggish mass transfer process. Herein, a functionalized aminated graphene-rich nickel–iron layered double hydroxide (NiFe-LDH@NH2-G) nanocomposite was successfully synthesized with a one-pot coprecipitation method that demonstrates onset potentials of 0.41 and 0.32 V for both OER and urea oxidation reaction (UOR), respectively, and both are lower than those of NiFe-LDH and NiFe-LDH@rGO under similar conditions. Moreover, the catalyst shows a mass activity of 0.356 mA mg–1 at 1.49 mV for the OER, which is 6.6 times higher than that of NiFe-LDH, and for the UOR, the mass activity was 0.368 mA mg–1 at 1.49 mV, which is 4.8 times higher than that of NiFe-LDH. The catalyst shows the lowest Tafel value of 49 mV dec–1 and possesses a high turnover frequency of 2.92 × 10–1 S1– for the OER. The aminated graphene-functionalized catalyst shows the lowest overpotential of 260 mV at 10 mA cm–2 compared to those of NiFe-LDH@rGO (300 mV) and NiFe-LDH@Graphene (290 mV) for the OER. The excellent catalytic activity is attributed to the incorporation of functionalized aminated graphene, which improves the electronic structure of the composite with the successful integration of nitrogen into the carbon matrix. The amine is an electron-withdrawing group, and its incorporation can eliminate the oxygen functional groups which increases the C/O ratio thereby enhancing the conductivity of the graphene layers, making a good case for the electrocatalyst. This is the first ever report where an aminated graphene-based nanocomposite is shown to have exceptional electrocatalytic activity and will is an important step toward design of a future electrocatalyst for OER and UOR.