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 Nix Co1-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 Nix Co1-x alloy strictly depended on the used amount of water owing to the different solubilities of the precursors. Among them, the Ni0.6 Co0.4 nanoparticles obtained with 70 μL 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 CH3 OH solution, which is higher than those of Ni0.7 Co0.3 (80 mA cm-2 ) and Ni0.5 Co0.5 (33 mA cm-2 ). The excellent performance of Ni0.6 Co0.4 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.