In this article, we focus on the understanding of the <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Pt</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">Co</mml:mi><mml:mi>y</mml:mi></mml:msub></mml:mrow></mml:math>PtxCoy electrocatalysts degradation in polymer electrolyte fuel cell (PEFC) environments. A multiscale atomistic/kinetic model is derived providing mechanistic insights on the impact of the nanostructure and operating conditions on <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Pt</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">Co</mml:mi><mml:mi>y</mml:mi></mml:msub></mml:mrow></mml:math>PtxCoy nanoparticles durability. On the basis of ab initio (AI) data, we identify favorable pathways of the oxygen reduction reaction (ORR) on <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Pt</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">Co</mml:mi><mml:mi>y</mml:mi></mml:msub></mml:mrow></mml:math>PtxCoy nanoparticles and of the competitive Pt–Co dissolution in acidic media. The derived AI kinetics is coupled to a description of the atomic reorganization at the nanoparticle level as a function of the cumulated Pt and Co mass losses. This nanoscale model is coupled with a transport microscale model of charges and <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>O2 through a PEFC cathode, and simulation sensitivity studies to operating conditions and initial compositions/morphologies are performed and complimented by microstructural and electrochemical characterizations carried out on aging direct liquid injection metallorganic chemical vapor deposition elaborated model electrodes detailed in our experimental companion paper.

Reducing the number of stages, energy costs and carbon footprint of recycling processes is essential to overcome environmental challenges. The interest in replacing the acids used in traditional hydrometallurgical methods with deep eutectic solvents (DES), which are less toxic and more environmentally friendly, has been growing. The aim of this study is to estimate the potential use of this class of solvents in an ionometallurgical process of leaching and electrodeposition to recover silver as part of the recycling of solar panels, a major challenge of the years to come. In the present work, a circular recycling concept based on an iron redox shuttle was studied to leach and recover silver via electrodeposition. Different DESs were evaluated in combination with a hexahydrated iron(III) chloride oxidizing agent. Ethaline DES has gained significant interest as it can attain a high silver leaching efficiency of 99.9% on crystallized silicon cell scraps at 75 °C. The promising results led to a comprehensive study of limits of this chemical system, focusing on the relation between the concentration of species (iron and water), the interfacial potential of silver (electrochemical measurements), and surface evolution (X-ray photoelectron spectroscopy analysis). Silver leaching was determined as a mixed control mechanism involving chemical and species diffusion dependence. The concentration of iron(III) chloride appeared crucial, determining the kinetic of formation of a poorly soluble AgCl layer. Electrodeposition from leachate highlighted the need to use an oxygen-free atmosphere to produce high-quality silver. Finally, leaching at 75 °C and electrodeposition at 50 °C of silver from crystallized silicon cell scraps were demonstrated using Ethaline (1 : 2) + FeCl₃·6H₂O (0.12 mol L⁻¹) under an argon atmosphere.