Visible-light-driven photoelectrocatalytic degradation of tetracycline using dual Z-scheme Bi2MoO6/GQDs/TiO2 heterojunctions

Abstract

Photocatalysis offers an effective approach for the treatment of refractory tetracycline (TC) contamination. Conventional TiO₂-based semiconductor photocatalysts for TC degradation are limited by their narrow spectral response range and rapid electron–hole recombination. In this study, ternary Bi₂MoO₆/graphene quantum dot/TiO₂ nanotube array (BGT) photocatalysts with dual Z-scheme heterojunctions were designed and synthesized to overcome these limitations. The removal efficiency of TC by BGT-2 photocatalysts in photoelectrocatalytic degradation reached 79.72% within 120 minutes, with an enhanced apparent reaction rate constant (K_app = 13.62 × 10⁻³ min⁻¹), representing a 2.41-fold enhancement compared to TiO₂ (5.65 × 10⁻³ min⁻¹). The optimized photocatalyst, BGT-2, exhibited a photocurrent density of 9.96 μA cm⁻² and a carrier density of 7.18 × 10²⁰ cm⁻³, demonstrating high charge separation efficiency. This enhanced photoelectrochemical performance was attributed to the formation of dual Z-scheme heterojunctions, which maintain the strong redox potentials of photogenerated carriers and reduce recombination losses. This work presents a novel material construction strategy for developing high-performance photocatalysts to address persistent antibiotic contamination.