PGM Recovery: Maximizing PGM Dissolution through Minimizing Ostwald Ripening

Abstract

Efficient recovery of platinum group metals (PGMs) through electrochemical means using mild conditions is of significant impact from both the industrial and the environmental points of view. Owing to their large surface-to-volume ratio, fast dissolution of PGM nanoparticles is possible through potential cycling between oxidizing and reducing potentials, leading to formation and dissolution of surface-oxide layer (transient dissolution). However, at reducing potentials, reduction of the dissolved metal species on the source nanoparticles leads to enhance the Ostwald ripening process1 and hence to decrease the overall dissolution efficiency significantly. In this talk, we present strategies to accelerate dissolution of PGM nanoparticles by limiting Ostwald ripening through (1) use of surface switching species (SSS), which selectively block the PGM surface to inhibit redeposition induced particle growth at reducing condition and expose the PGM surface to facilitate dissolution at oxidation condition, respectively2. (2) use of an auxiliary deposition system to continuously remove the dissolved PGM species through reaction kinetic manipulation3. Such surface relegation property to depress unwanted process and assist desired reaction documents an alternative and efficient approach for precious metal electrochemical recovery. References Sharma, R.; Andersen, S. M., Quantification on Degradation Mechanisms of Polymer Electrolyte Membrane Fuel Cell Catalyst Layers during an Accelerated Stress Test. ACS Catal. 2018, 8 (4), 3424-3434.Sharma, R.; Simonsen, S. B.; Morgen, P.; Andersen, S. M., Inhibition of Ostwald ripening through surface switching species during potentiodynamic dissolution of platinum nanoparticles as an efficient strategy for platinum group metal (PGM) recovery. Electrochim. Acta 2019, 321, 11.Sharma, R.; Gyergyek, S.; Andersen, S. M., Environmentally and Industrially Friendly Recycling of Platinum Nanoparticles Through Electrochemical Dissolution-Electrodeposition in Acid-Free/Dilute Acidic Electrolytes. ChemSusChem 2018, 11 (21), 3742-3750.