Leaching Efficiency and Kinetics of Platinum from Spent Proton Exchange Membrane Fuel Cells by H2O2/HCl

Abstract

The increasing carbon emissions from various fossil fuels have led to the search for efficient and clean energy sources to replace them. Proton exchange membrane fuel cells (PEMFCs) are a promising alternative, but the use of platinum as a catalyst material poses challenges due to its limited resources and low abundance. This study proposes an efficient method for platinum recovery while retaining spent membranes. The membrane and catalyst were separated using isopropanol, and the spent membrane was dissolved in a 50% ethanol solution to prepare the precursor for subsequent membrane regeneration. Hydrochloric acid (HCl) was used as the leaching agent, and the experimental parameters such as HCl concentration, H2O2 concentration, contact time, and operating temperature were optimized to achieve the highest platinum leaching rate. Finally, through isothermal leaching experiments, the leaching mechanism was investigated using the shrinking core model, indicating the involvement of both surface chemical and inner diffusion mechanisms in the platinum leaching process, primarily controlled by the inner diffusion mechanism. Under optimal conditions, the platinum leaching rate was about 90%, and the activation energy of the reaction was calculated to be 6.89 kJ/mol using the Arrhenius equation.

Fast Structural Dynamics in Concentrated HCl Solutions: From Proton Hopping to the Bulk Viscosity

“…Acid solutions have been studied extensively to understand their fundamental nature − and because of their central roles in technological applications such as water purification, fuel cells, and regeneration of ion exchange resins as well as in the food, textile, metal, and rubber industries. − Since proton diffusion was shown to be the main feature that gives rise to the bulk properties of acid solutions, most of the fundamental research in this area has focused on the properties and dynamics of the proton transfer. − Protons in, e.g., HCl solutions diffuse much faster than small cations in salt solutions, such as NaCl, or water molecules because protons move through the relay mechanism instead of diffusion by the vehicular mechanism associated with metal cations. , The relay mechanism involves the transfer of a proton from a hydronium cation to an adjacent water molecule . While hydronium also undergoes translational diffusion as the entire cation (vehicular mechanism), fast proton hopping between adjacent water molecules is typically the major contributor to proton transport …”