Water-mediated recycling of gold, palladium and platinum using semimetallic TiS2 and TaS2 nanosheets

The intensive and irreplaceable consumption of precious metals (PMs) including gold (Au), palladium (Pd) and platinum (Pt) in the electronic and catalysis industries, coupled with their scarcity in Earth's crust, demand innovative recycling solutions for PM sustainability. However, efforts to recycle PMs from leachates of their waste are frustrated by an unsatisfactory extraction capacity at low concentrations and remain predominantly focused on gold, leaving other PMs largely unexplored. We report the ultrahigh reductive recycling of PM ions and their simultaneous aqueous-phase deposition on semimetallic transition-metal dichalcogenides of TiS₂ and TaS₂ nanosheets_. Notably, TiS₂ shows unprecedentedly high extraction capacities of ∼8, 2.3 and 1.15 g/g for Au, Pd and Pt ions, respectively, and the adsorbed PM ions are directly transformed into nanoparticles deposited on the nanosheets. Mechanistic studies reveal that water-mediated electron donation from the sulfur site of the semimetallic TiS₂ and TaS₂ nanosheets is responsible for the ultrahigh extraction capacity, with a single TiS₂ molecule donating >13 electrons to gold ions. This electron transfer is mediated by the formation of sulfur-oxygen species during water dissociation. We further demonstrate the selective and complete recovery of Au, Pd and Pt from real-world waste streams including electronic waste, spent catalysts and automotive catalytic converters.