Nickel and cobalt in situ grown in 3-dimensional hierarchical porous graphene for effective methanol electro-oxidation reaction

Here we report, an efficient, cheap and simple strategy to obtain electrocatalysts for methanol electro-oxidation reactions. Nickel encapsulated 3-dimensional hierarchical porous graphene and cobalt encapsulated 3-dimensional hierarchical porous graphene composites are obtained by ion exchange/activation method. The well dispersion of nickel and cobalt nanoparticles are observed inside the nickel encapsulated 3-dimensional hierarchical porous graphene and cobalt encapsulated 3-dimensional hierarchical porous graphene composites respectively. Graphene layer over the metals nanoparticles may suppress metal corrosion and enhance their catalytic performance for methanol electro-oxidation reactions. Nickel encapsulated 3-dimensional hierarchical porous graphene exhibits low onset potential of 0.32 V (vs Ag/AgCl) and the highest current density of 147.108 mA cm−2 at a low overpotential of 0.728 V (vs Ag/AgCl). Similarly, cobalt encapsulated 3-dimensional hierarchical porous graphene shows lower onset potential of 0.45 V (vs Ag/AgCl) and high current density of 10 mA cm−2 at low overpotential of 0.62 V (vs Ag/AgCl). More importantly, better methanol electro-oxidation reaction was recorded in 1 M KOH and 0.75 M methanol solution with a scan rate of 50 mV s−1. The nickel-containing electrocatalyst show better performance than cobalt based electrocatalyst under same conditions.