Unusual Effect of Trace Water on the Structure and Activity of NixCo1-x Electrocatalysts for the Methanol Oxidation Reaction

Highly active Ni-based catalysts have attracted much attention but are still facing challenges owing to the immature synthetic method. Herein, polyhedral NixCo1-x alloy was prepared by a facile modified polyol method in which a trace amount of water could halve the particle size of the alloy. The Ni/Co ratios in NixCo1-x alloy strictly depended on the used amount of water owing to the different solubilities of the precursors. Among them, the Ni0.6Co0.4 nanoparticles obtained with 70 mu L of deionized water exhibited the best performance in the methanol oxidation reaction with a peak current density of 116 mA cm(-2) in the presence of 1 m NaOH+0.5 m CH3OH solution, which is higher than those of Ni0.7Co0.3 (80 mA cm(-2)) and Ni0.5Co0.5 (33 mA cm(-2)). The excellent performance of Ni0.6Co0.4 is attributed to the unique structure with appropriate Ni/Co ratio, which elongates the C-O bond in methanol and lowers the reaction free energy according to DFT calculations.