en.Wedoany.com Reported - Researchers at the University of Newcastle, in collaboration with CSIRO Energy and PV Industries, systematically investigated the electrochemical factors affecting silver recovery efficiency during solar panel recycling, with a focus on the roles of electrode materials, current density, and copper contamination on silver electrodeposition behavior.
The research team noted that although silver accounts for only about 0.03% of the weight of photovoltaic modules, it contributes half of the module's material value. Based on current projections, 85% to 95% of global silver reserves could be locked into photovoltaic modules by 2050. While previous literature has experimentally explored electrochemical recovery of silver from photovoltaic cells, studies on the underlying process variable influence mechanisms remain limited.
In the experiments, the team prepared a silver leaching electrolyte containing 4 M nitric acid (HNO₃) and 20 mM silver nitrate (AgNO₃) to simulate the silver solution dissolved from recycled solar cells. This electrolyte was subsequently evaluated in a three-electrode electrochemical cell equipped with four cathode materials: silver, 316L stainless steel, copper, and graphite. After identifying the optimal electrode material, the researchers further analyzed the effects of current density and copper concentration on silver deposition. Current densities were set at −5, −20, −35, and −50 mA cm⁻², while copper concentrations in the electrolyte were adjusted to 10, 20, and 30 mM, respectively. Silver recovery rate, faradaic efficiency, deposition potential, deposit morphology, and purity were characterized using gravimetric analysis, cyclic voltammetry, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD).
The results showed that stainless steel electrodes delivered performance comparable to silver electrodes, achieving an average recovery rate of 93% and a faradaic efficiency of 92%, while demonstrating greater stability, with no contamination observed in the deposited silver. Copper electrodes were unstable in the electrolyte and dissolved during deposition; graphite electrodes failed to produce consistently stable silver deposits.
After identifying 316L stainless steel as the most suitable electrode material, the team examined its performance under different current densities. The results revealed that increasing current density simultaneously improved both silver recovery rate and faradaic efficiency—rising from 87% and 86% at −5 mA cm⁻² to 93% and 96% at −35 mA cm⁻². However, beyond this value, both metrics declined. Additionally, current density had a significant impact on deposit morphology, with deposited particle sizes tending to decrease as current density increased.
The study also found that copper concentration in the electrolyte had a notable effect on the system's electrochemical behavior, as confirmed by cyclic voltammetry measurements. Copper concentration also appeared to influence the nucleation and deposition processes of silver, thereby altering deposit morphology. However, within the tested concentration range (up to 30 mM copper and 20 mM silver), no evidence of copper co-deposition was observed in the deposited silver.
The findings were published in the journal Electrochimica Acta under the title "A parametric analysis of electrochemical variables in silver recovery for solar module recycling."
