Dual step-scheme heterojunction with full-visible-light-harvesting towards synergistic persulfate activation for enhanced photodegradation

The occurrence of micropollutants in aquatic media raises great concern because of their biological toxicity and persistence. Herein, visible-light-driven photocatalyst titanium dioxide/graphitic carbon nitride/triiron tetraoxide (TiO_2-x/g-C₃N₄/Fe₃O₄, TCNF) with oxygen vacancies (O_v) was prepared via a facile hydrothermal-calcination method. The complementary visible-light co-absorption among semiconductors enhances light-harvesting efficiency. The built-in electric field formed during Fermi level alignment drives photoinduced electron transfer to improve charge separation across the interfaces. The increased light-harvesting and favorable energy band bending significantly enhance the photocatalytic performance. Therefore, TCNF_-5-500/persulfate system could effectively photodegrade bis-phenol A within 20 min under visible-light irradiation. Moreover, the superior durability, non-selective oxidation, adaptability, and eco-friendliness of the system were confirmed by different reaction conditions and biotoxicity assessment. Furthermore, the photodegradation reaction mechanism was presented according to the major reactive oxygen species produced in the system. Thus, this study constructed a dual step-scheme heterojunction by tuning visible-light absorption and energy band structure to increase the charge transfer efficiency and photogenerated carrier lifetime, which has great potential for environmental remediation using visible photocatalysis.

Hierarchical TiO2-x nanoarchitectures on Ti foils as binder-free anodes for hybrid Li-ion capacitors

Hybrid Li-ion capacitor (LIC) draws more attention as novel energy storage device owing to its high power density and high energy density. Designing three-dimensional electrode materials is beneficial for improving electrochemical performance of LICs. Herein, an improved hydrothermal method combined with an ion-exchange reaction is used to manufacture oxygen vacancies (OVs)-doping TiO₂ (TiO_2-x) nanowires/nanosheets (NWS) on Ti-foil. Then TiCl₄ treatment is performed to form TiO_2-x NWS/nanocrystallines (NWSC). These-obtained hierarchical nanoarchitectures assumes enrich electro-active sites and contact areas, which can improve electron transference and structural stability. The TiO_2-x NWSC is used as binder-free anode for Li-ion battery and achieves high specific capacity (300 mAh g^-1 at 0.1 A g^-1), excellent rate capability (102 mAh g^-1 at 5 A g^-1) and long cycle stability (44% after 1000 cycles at 1 A g^-1). LICs assembled with a TiO_2-x NWSC anode and an activated carbon cathode have an energy density of 44.2 W h kg^-1 at the power density of 150 W kg^-1. Therefore, the TiO_2-x NWSC is a potential candidate for high energy and high power electrochemical energy storage devices.