Polyaniline-ZnTi-LDH heterostructure with d-π coupling for enhanced photocatalysis of pollutant removal

Heterointerface engineering is an effective strategy to design and construct high-performance photocatalysts. Herein, polyaniline (PANI) nanoparticles and ZnTi layered double hydroxide (ZnTi-LDH) nanosheets were integrated to form organic-inorganic heterostructure (PANI/LDH) via d-π electronic coupling using in-situ polymerization for photocatalytic oxidation/reduction towards tetracycline (TC) and Cr(VI). The photocatalytic activity was closely related to feed amount of aniline (Ani) in the polymerization process, which the abundant PANI nanoparticles were evenly distributed on the surface of ZnTi-LDH nanosheets at the proper Ani feed amount, and thus reinforced d-π electronic coupling at the organic-inorganic interfaces more efficiently. Density functional theory calculations further verified the existence of d-π overlap at the PANI/LDH heterointerface. The strong d-π coupling boosted charge separation and transfer to improve photocatalytic efficiency. As a result, the optimal PANI/LDH_(0.3) exhibited outstanding photocatalytic activities with 97.8 % Cr(VI) reducing rate and 87.8 % TC removal rate in the single Cr(VI) and TC system, as well as high simultaneous removal rate of Cr(VI) and TC in TC/Cr(VI) coexistence system, respectively. Subsequently, the photocatalytic enhanced mechanisms were put forward to remove Cr(VI) and TC under visible-light. Finally, the aquatic toxicity of the photolytic products was evaluated using Chlorella sp. as an ecological indicator, showing that the PANI/LDH had a notable detoxification efficiency of TC and Cr(VI).