3D NiCr-layered double hydroxide/reduced graphene oxide sand rose-like structure as bifunctional electrocatalyst for methanol oxidation

Three-dimensional (3D) structures are currently a topic of considerable interest due to their extraordinary properties. In this work, a 3D hybrid nanocomposite nickel-chromium layered double hydroxide (NiCr-LDH) was in-situ synthesized on different concentrations of reduced graphene oxide (rGO) using a microwave-assisted method. The structural and morpholological analysis of the as-prepared nanocomposites were characterized by XRD, SEM, TEM, FTIR and BET. The nanocomposite contains the highest amount of rGO (200 mg) shows a 3D sand rose-like structure which considered as a benifit for electrocatalytic reactions. The 3D structure of the hybrid NiCr-LDH/rGO nanocomposites exhibited much higher performance for methanol oxidation than the pure NiCr-LDH catalyst where the nanocomposites surface became more open, thus providing minor resistance for mass transport. Thus, an electron pathway can be easily formed and a network of stress transfer can be also presented. Using 3 M methanol at scan rate of 60 mVs(-1), the obtained current density was found to be 0.54, 0.97, 1.39 and 2.22 mA/cm(2) for G0-LDH, G50-LDH, G100-LDH and G200-LDH, respectively. These enhancements confirmed that the 3D structure of the NiCr-LDH with rGO can guarantee an efficient use of the catalyst. Furthermore, the sand rose-like structure of G200-LDH sample exhibited the lowest onset potential 0.3 V. This work will open the door toward fabrication of 3D sand rode-like structure to be used in different electrocatalytic reactions.