Outstanding Platinum Recovery by Electrochemical Cathodic Leaching and Redeposition in One-Pot 2 M HCL Solution

Abstract

Selective Pt recovery from spent Pt/C gas diffusion electrodes (GDE) is essential for sustainable proton exchange membrane fuel cell and electrolysis industry. This study presents a promising, environmentally friendly approach using pulsed electrochemical cathodic leaching (ECCL) and subsequent electrochemical cathodic deposition (ECCD) in one pot diluted HCl solution. The parameters of ECCL pulse signal were optimized by varying electrolyte concentration, cell voltage, duty cycle, pulse number, and pulse sequence. For aging of GDE, a standard accelerated degradation tests protocol was applied. The amount of dissolved Pt in the electrolyte was evaluated by UV–vis absorption peak intensity at 260 nm that is assigned to Pt (IV) chloro complex ions. A Pt dissolution rate of 99.8% from fresh and aged GDE was achieved in 2 M HCl by applying cell voltage of “only” −3 V (cathode potential: −0.55 V vs RHE) and combining long and short pulse voltage sequences. Remaining Pt in the electrode were determined from electrochemical surface area and thermogravimetric analysis profiles confirming UV–vis results. Finally, proof of concept of one-pot Pt recovery from ECCL electrolyte by means of ECCD step was demonstrated.