Mechanochemically Transforming Waste Ceramic Capacitors into Self-Doped BaTiO₃ Photocatalysts: An Efficient Approach for High-Value E-waste Recycling and Hydrogen Production

Waste ceramic capacitors, which are widely present in e-waste and rich in BaTiO3, Ag, Sn, Ni, and others, are valuable resources for recycling. Traditional pyrometallurgy and hydrometallurgy methods for separating metal elements from these capacitors are energy-intensive, involve lengthy processing steps, and generate waste liquids. This study breaks through the traditional idea of separating metal elements and proposes a one-step and efficient ball milling approach to directly transform the full compositions of waste ceramic capacitors into self-doped BaTiO3 photocatalysts without the need for chemical reagents. The influences of ball-milling time and ball-to-waste ratio on the microstructural characteristics, optical properties, charge separation efficiency, and photocatalytic H2 generation of the photocatalysts were investigated to reveal the mechanochemical effects and optimize the photocatalytic performance. The sample with a ball-to-waste ratio of 20:1 and ball-milling time of 1 h yielded small, uniform particles with high light absorption and charge separation, resulting in exceptional H2 production of 191.3 μmol g–1 h–1. Our findings demonstrate the mechanochemical effects on the synthesis and optimization of self-doped BaTiO3 photocatalysts from waste ceramic capacitors. This study also provides a strategy for directly recycling the full components of e-waste into functional materials without chemical consumption, thus avoiding the generation of waste liquids and achieving eco-friendly and high-value recycling of e-waste.