Novel CuNiAl-LDH-rGO immobilized Cu2O nanocubes photocatalyst with Z-scheme heterostructure for enhanced visible-light-driven degradation of tetracycline

Abstract

A series of novel heterostructured photocatalysts Cu₂O/Cu_xNi_3-xAl-LDH-rGO hybrids (x = 0.5, 1 and 1.5) were synthesized by co-precipitation method followed by in-situ reduction, where rGO acted as an electron transfer bridge between LDH and Cu₂O. By adjusting the Cu/Ni ratio in LDH, the optical and photoelectrochemical properties and photocatalytic performances of the hybrids were optimized. As expected, the optimal Cu₂O/Cu₁Ni₂Al-LDH-rGO heterojunction showed superior photocatalytic performance, achieving 93 % tetracycline (TC) degradation within 70 min. Systematic characterization demonstrated that the atomic-level Cu²⁺ ions in the LDH layers were partially reduced to highly dispersed Cu₂O nanocubes (∼15 nm) and thereby the p-n heterojunctions were successfully constructed, which is beneficial for the enhancement of photocatalytic properties. The catalyst was stable and reusable with only a 7 % reduction in removal efficiency after 5 successive cycles. Mechanism investigation revealed that the formation of rGO-mediated Z-scheme heterojunction contributed to the enhanced photocatalytic efficiency, promoting the separation of photoexcited electron-hole pairs and maintaining high redox ability during the photocatalytic process. The effectiveness of photocatalytic degradation in reducing toxicity was validated through the cultivation of soybean sprouts.