Auspicious Metal-Doped-Cu2O/Cu Dendrite (M=Ni, Co, Fe) Catalysts for Direct Alkaline Fuel Cells: Effect of Dopants

Abstract

Herein, honeycomb nickel-, cobalt- and iron-doped Cu2O/Cu foams with dendrite-like structures are in-situ formed atop of a copper foil substrate using the facile and low-cost dynamic hydrogen bubbles template technique (DHBT), wherein the copper nanoparticles are electrodeposited and grow in the interstitial spaces between the hydrogen bubbles. The incorporation of nickel, cobalt and iron impurities (less than 4%) in the Cu2O/Cu structures improved the performance of Cu2O/Cu significantly for various electrochemical reactions (i.e., water splitting, glucose and glycerol electrooxidation). Besides, only minor additions of these transition metals are dramatically changed the average particle size and morphology of the deposited copper nanoparticles. For instance, the un-doped Cu2O/Cu foam showed an artichoke flower-like structure (particle size ~150 nm) which is converted into a grape cluster-like structure (~92 nm), corncob-like structure (~58 nm) and grass-like structure (~78 nm) with nickel, iron and cobalt particles doping. The iron-doped Cu2O/Cu dendrites exhibited 7 and 4 times higher electrocatalytic activity along with 230 mV and 190 mV negative shift of the glucose and glycerol electro-oxidation peak compared to the un-doped Cu2O/Cu structures. This outstanding enhancement is attributed to the catalysts dendritic structures providing an accessible high active surface area. In addition, the doped metals are believed to increase the electrochemically active surface area and to facilitate the electron transfer in the studied reactions. Besides, the existence of these dopants improved the adsorption of glucose and glycerol molecules on the copper surface active sites together with increasing of the Cu2O inherent conductivity. Figure 1