Bifunctional ultrathin CoAl-LDHs/g-C3N4 type-II heterojunction: Photocatalytic degradation of ciprofloxacin and hydrogen production

Construction of ultrathin CoAl-LDHs/g-C 3 N 4 Type-II heterojunction via an electrostatic self-assembly. • Type-II band alignment suppresses charge recombination and boosts charge separation. • Bifunctional design enables efficient H 2 evolution and pollutant degradation. • In-situ XPS and DFT calculations validate the proposed charge transfer pathway. Constructing efficient and stable heterojunction photocatalysts was crucial for achieving bifunctional applications in antibiotic degradation and photocatalytic hydrogen production. Herein, an ultrathin CoAl-LDHs/g-C 3 N 4 Type-II heterojunction was successfully fabricated via an electrostatic self-assembly strategy, and its performance was systematically evaluated for both ciprofloxacin (CIP) degradation and visible-light-driven hydrogen evolution reaction (HER). The optimal CAC2 sample (CAC2, mass ratio of 1:2) achieved a CIP degradation efficiency of 84.9%, which was 1.9-fold and 3.3-fold higher than those of pristine CoAl-LDHs (CAL) and g-C 3 N 4 (CN), respectively. Meanwhile, it delivered a remarkable hydrogen evolution rate of 1935.67 μmol·g −1 ·h −1 , which was 263.3 and 6.5 times higher than those of pristine CAL and CN, respectively. The significantly improved hydrophilicity of the heterojunction enhanced the interfacial enrichment of CIP. Active species trapping experiments confirmed that h + acted as the dominant reactive species, while ·O 2 - played an auxiliary role. Combining XPS, work function calculations, and in situ XPS under light irradiation, we strongly indicate that electrons spontaneously transfer from CAL to CN in the dark, establishing a built-in electric field (BIEF) oriented from CAL to CN. Upon light excitation, the photogenerated electrons migrate from CN to CAL following the typical Type-II pathway, which together with the BIEF synergistically facilitates spatial charge carrier separation. This study elucidated the structure-activity relationship of the electrostatic self-assembled Type-II heterojunction for bifunctional photocatalysis, offering a new paradigm for designing efficient and robust catalytic materials for environmental and energy applications. Download: Download high-res image (253KB) Download: Download full-size image