Platinum recycling through electroless dissolution under mild conditions using a surface activation assisted Pt-complexing approach.

High industrial demand and limited global abundance of precious metals (PMs) make their recycling essential for the industrial and societal sustainability. Owing to their high surface-to-volume ratio, recycling of nanoparticulate precious metals through dissolution in dilute acids at room temperature is quite relevant. However, their dissolution by approaches such as the cyclic oxidation-reduction of metal surface through surface potential manipulation may not be suitable for large-scale production. Here, we demonstrate fast dissolution of Pt-nanoparticles under mild conditions (normal temperature and pressure) in Cl- containing dilute acidic/neutral baths without using the cyclic oxidation-reduction. We demonstrate that the dissolution of Pt nanoparticles through [PtClx]2- complexing is hindered by blockage of the Pt surface due to adsorption of non-oxide species (impurities), a phenomenon termed herein as non-oxide passivation (NOP). The nanoparticles can be kept active for the [PtClx]2- complexing through removal of the adsorbed species by surface activation, a process to remove the NOP layer by application of a cyclic/continuous perturbation. As an example, average % dissolution rate increases from ~10%/h (~30% dissolution in 3 h) for dissolution without NOP removal to ~19%/h (~55% dissolution in 3 h) for dissolution through cyclic activation of the Pt surface by HCl−water cycling. The approach may be implemented with a range of cost-efficient and non-toxic reagents for industrial-scale- and environmentally friendly recycling of Pt.