Direct recycle waste silicon wafer as the charge transfer bridge to assemble a Z-scheme heterojunction for enhanced photocatalytic performance

The retirement wave of photovoltaic (PV) panels is expected to result in a significant number of discarded panels in the near future. Recycling PV silicon in a rational manner will not only help reduce the environmental impact but also lead to substantial economic gains. In this study, aaste solar silicon wafers were ball-milled to obtain recycled silicon (r-Si) powder. The TiO2/r-Si carrier was prepared through a simple hydrothermal process, followed by the creation of a novel Ag3PO4/TiO2/r-Si (APO/TIO/r-Si) ternary heterojunction composite using a co-precipitation method. The photocatalytic properties of the materials doped with different concentrations of Ag3PO4 were examined using Rhodamine B (RhB) degradation rate as a performance metric. Among them, 40 %APO/TIO/r-Si heterojunction exhibits excellent photodegradation activity under visible light irradiation. The photocatalytic degradation efficiency reached 93.0 % in 30 min, with a removal rate of 82.8 % after 5 cycles. It was found that superoxide radicals and hydroxyl radicals are the main drivers of RhB photodecomposition. The decomposition pathways of RhB dye were identified using high performance liquid chromatography mass spectroscopy (HPLC-MS), revealing N-de-ethylated intermediates as the main intermediate. The photoreaction mechanism and RhB degradation pathway over APO/TIO/r-Si were elucidated, showing a direct Z-Scheme heterojunction electron transfer pathway with r-Si acting as charge transfer center. The formation of the heterojunction not only minimizes interfacial resistance effectively but also enhances disintegration and preservation of photo-carriers, leading to improved photo-redox ability and increased photoactivity. This study presents a win–win approach for recycling waste silicon wafers from retired PV panels as potential heterojunction photocatalysts for efficient photocatalytic oxidation of dye contamination.