The optimal design of Co catalyst morphology on a three-dimensional carbon sponge with low cost, inducing better sodium borohydride electrooxidation activity

A low-cost nano-flake Co@carbon sponge (Co NF@carbon sponge) electrode is prepared by a simple sponge carbonization method coupled with direct Co growth on the carbon sponge surface using pulsed electrodeposition. The catalytic activity of sodium borohydride (NaBH4) electrooxidation in an alkaline medium are studied by cyclic voltammetry (CV) and chronoamperometry (CA). The Co NF@carbon sponge electrode reveals a unique three-dimensional (3D) nano-flake structure on the porous network skeleton with a large specific surface area and exhibits superior catalytic performance. The oxidation current density of the Co NF@carbon sponge electrode towards NaBH4 achieves 248 mA cm−2 in 1 mol L−1 NaOH and 0.12 mol L−1 NaBH4 solution at −0.55 V (vs. Ag/AgCl) accompanied with a considerable stability, which is remarkably higher than the electrocatalytic performance of NaBH4 oxidation obtained previously with non-noble metals as catalysts. The induced high catalytic activity greatly contributes to the excellent 3D nano-flake open structure and high electronic conductivity, which guarantees the full utilization of Co surfaces and allows the electrode to possess higher electrocatalytic performance. The novel Co NF@carbon sponge electrode is a hopeful anode with low cost and high performance for the application of fuel cells that employ NaBH4 as the fuel.