Valorization of Gold Recovered from Electronic Waste for the Synthesis of Au/TiO2 Photocatalysts for Hydrogen Generation in Methanol–Water Solution

This study explores the valorization of gold recovered from electronic waste (e-waste) processors by converting it into functional Au/TiO2 photocatalysts for hydrogen production. The gold coatings were selectively recovered and converted to HAuCl₄ using a mild acid medium without aqua regia, followed by the synthesis of Au/TiO2 materials with nominal loadings of 0.25, 0.50, 1.0, and 2.0 wt% via urea precipitation. Electron microscopy analyses (TEM, STEM-HAADF, SAED, HRTEM) revealed well-dispersed Au nanoparticles at low loadings and increased particle growth and agglomeration at higher gold contents. X-ray photoelectron spectroscopy showed that gold is predominantly present as metallic Au⁰, with an increasing contribution of Au³⁺ species as the loading increases. Photocatalytic tests conducted in a methanol-water system under UV irradiation yielded hydrogen evolution rates of 12.8, 20.8, 25.5, and 27.6 mmol g-1 h-1 for 0.25, 0.50, 1.0, and 2.0 wt% Au/TiO2, respectively, with the 1.0 wt% sample achieving nearly the same activity as the 2.0 wt% material despite using only half the amount of gold. These results indicate that gold recovered from electronic waste can be transformed into effective photocatalysts and that optimal hydrogen production can be achieved with moderate gold loadings, supporting a waste valorization strategy for sustainable energy applications.