Direct Observation of Palladium Leaching from Pd/C by a Simple Method: X-ray Absorption Spectroscopy of Heterogeneous Mixtures.

Herein, we show the detailed behavior of palladium leaching from palladium on charcoal by aqueous HCl, directly observed by X-ray absorption spectroscopy measurement employing a simplified reaction setup. While Pd 0 is not affected by the addition of HCl, palladium oxide in nanoparticles readily reacts with HCl to form the ionic species [Pd II Cl 4 ] 2- , even though these ions mostly remain adsorbed on the surface of activated charcoal and can only be detected at a low level in the solution phase. This finding provides a new aspect for control of the leaching behavior and robust usage of palladium on charcoal in organic reactions.