Controlling Palladium Nanocrystals by Solvent-Induced Strategy for Efficient Multiple Liquid Fuels Electrooxidation

Pd has been considered as the possible economical substitute of rare Pt for catalyzing the liquid fuels electrooxidation reaction. However, the biggest problem of Pd nanocatalysts for alcohol oxidations is that they show the limited stability and activity, greatly impacting the development of liquid fuels-based fuel cell technology. We report herein a new solvent-induced procedure for making distinct Pd NCs with geometry tuning from Pd nanosheets, Pd tetrapods, to Pd concave tetrahedra by switching the solvent from 1-methyl-2-pyrrolidone, formamide, to acetylacetonate. The key features for the preparation of dimension-controlled Pd NCs herein are that the use of molybdenum carbonyl (Mo(CO)6) determines the exposed {111} facet in the final Pd NCs, while different solvents control the reduction kinetics to induce the growth of Pd NCs with distinct morphologies. The as-prepared distinct Pd NCs show the interesting shape-dependent electrocatalytic activities toward multiple liquid fuels electrooxidation reactions including ethylene glycol oxidation reaction, glycerol oxidation reaction, ethanol oxidation reaction, and also methanol oxidation reaction with Pd nanosheets exhibiting higher activity than all the other Pd catalysts and higher activity than the commercial Pd/C and also Pd black due to the thin character of Pd nanosheets. Most importantly, the Pd nanosheets exhibit much higher stability for multiple liquid fuels electrooxidation than all the other Pd catalysts tested. The present work gives the first example in exploring the effect of solvent in tuning the dimensions of Pd NCs, and thus optimizing the electrocatalytic performance for liquid fuels electrooxidation.