Utilizing E-Waste for Construction of Magnetic and Core–Shell Z-Scheme Photocatalysts: An Effective Approach to E-Waste Recycling

The increasingly large stream of e-waste is seriously threatening the environment; meanwhile, global energy shortage is on the rise. Based on the principles of energy regeneration and waste utilization, we introduced a win-win approach to utilize waste capacitors for construction of magnetic and core–shell Z-scheme Nb–Pb-codoped BaTiO3/Ni–Pd@graphite-like carbon nitride (g-C3N4) photocatalysts for H2 evolution. Using simple ball-milling, waste capacitors were transformed to Nb–Pb-codoped BaTiO3/Ni–Pd–Ag–Sn nanoparticles and g-C3N4 was coated on the nanoparticles, forming a core–shell structure. The Ni–Pd acted as the electron mediator in the Z-scheme, and Ag–Sn also facilitated the electron transfer. Moreover, Ni made the Z-scheme magnetically separable. The Z-scheme showed a remarkably enhanced photocatalytic H2 evolution rate, which was 22.2 times higher than that of g-C3N4. Such an enhanced photocatalytic performance was attributed to the special Z-scheme and core–shell structure, improving the light adsorption, increasing the Brunauer–Emmett–Teller (BET) surface area, facilitating the efficient separation of electron–hole pairs, and maintaining the strong redox ability of charge carriers. Furthermore, the photoluminescence analysis combined with density functional theory (DFT) calculations provided the basis for the Z-scheme mechanism. This study adequately utilized the composition of e-waste to construct a highly efficient and magnetically separable Z-scheme for H2 generation, which realizes energy regeneration, waste recycling, and environmental protection.