How to Remove the Capping Agent from Pd Nanocubes without Destructing Their Surface Structure for the Maximization of Catalytic Activity?

We report a robust method for effectively removing the chemisorbed Br⁻ ions, a capping agent, from the surface of Pd nanocubes to maximize their catalytic activity. The Br⁻ ions can be removed by simply heating the sample in water, but the desorption of Br⁻ ions will expose the underneath Pd atoms to the O₂ from air for the formation of a relatively thick oxide layer. During potential cycling, the oxide layer evolves into detrimental features such as steps and terraces. By introducing a trace amount of hydrazine into the system, the Br⁻ ions can be removed by heating without forming a thick oxide layer. The as-cleaned nanocubes show greatly enhanced activity toward formic acid oxidation. This cleaning method can also remove Br⁻ ions from Rh nanocubes and it is expected to work for other combinations of nanocrystals and capping agents.