Modulating interfacial charge migration in g‑C3N4/Zn-Sr0.25H1.5Ta2O6·H2O heterostructures for accelerated drug contaminant degradation

Abstract To address the bottlenecks of low visible-light utilization, rapid carrier recombination, and insufficient active sites of pristine photocatalysts for contaminant degradation, step-scheme (S-scheme) g-C 3 N 4 /Zn-Sr 0.25 H 1.5 Ta 2 O 6 ·H 2 O photocatalysts were synthesized via a combined calcination-solvothermal method. The photocatalytic performance towards tetracycline degradation and enhancement mechanism were systematically explored by integrating multiple characterization techniques. The synthesized g-C 3 N 4 /Zn-Sr 0.25 H 1.5 Ta 2 O 6 ·H 2 O composites exhibited improved photocatalytic performance, with a maximum apparent rate constant (k) of 0.12269 min -1 , 3.69, 38.22, and 2.65 times those of Sr 0.25 H 1.5 Ta 2 O 6 ·H 2 O, g-C 3 N 4 , and binary g-C 3 N 4 /Sr 0.25 H 1.5 Ta 2 O 6 ·H 2 O, respectively. This work systematically deciphered the synergistic mechanism between Zn-doping and S-scheme heterojunction, as probed by in-situ X-ray photoelectron spectroscopy (XPS) measurements that directly demonstrated the directional migration of photogenerated carriers. Zn-doping broadened the optical absorption and created more active sites for tetracycline adsorption and surface degradation reaction, while the constructed S-scheme heterostructures effectively promoted the separation and directional migration of photogenerated carriers for tetracycline degradation. This study not only provides novel theoretical insights and experimental references for the precise design and controllable synthesis of element-doped S-scheme heterojunctions but also offers a promising strategy for environmental remediation of refractory organic pollutants.