A highly active Z-scheme NiGa2O4/anthraquinone/MoO3 photocatalyst via charge transfer for sunlight photocatalytic simultaneous conversions of nitrite and sulfite

Selective Bonding Effect of Heterologous Oxygen Vacancies in Z-Scheme Cu2O/SrFe0.5Ta0.5O3 Heterojunctions for Constructing Efficient Interfacial Charge-Transfer Channels and Enhancing Photocatalytic NO Removal Performances

An interfacial structure is crucial to the photoinduced electron transport for a heterostructure photocatalyst. Constructing an interfacial electron channel with an optimized interfacial structure can efficiently improve the electron-transfer efficiency. Herein, the rapid electron-transfer channels were built up in a Cu₂O/SrFe_0.5Ta_0.5O₃ heterojunction (Cu₂O/SFTO) based on the selective bonding effect of heterologous surface oxygen vacancies in the SFTO component. The heterologous surface oxygen vacancies, namely, V_O-Fe and V_O-Ta, respectively, adjacent to Fe and Ta atoms, were introduced into fabricating the Z-scheme Cu₂O/SFTO heterojunction. Compared with sample Cu₂O/SFTO with V_O-Fe, the photocatalytic NO removal efficiency of sample Cu₂O/SFTO with V_O-Fe and V_O-Ta was increased by 22.5%. The enhanced photocatalytic performance originated from the selective bonding effect of heterologous V_O-Fe and V_O-Ta on the interfacial electron-separating and -transfer efficiency. V_O-Fe is the main body to construct the interfacial electron-transfer channels by forming interfacial Fe-O-Cu(I) bonds, which causes lattice distortion at the interface, and V_O-Ta can optimize the structure of interfacial channels by balancing the electron density of SFTO to control the average space of the interface transition zone. This research provides a new cognitive perspective for constructing double perovskite oxide-based heterostructure photocatalysts.

Design and performance of a novel direct Z-scheme NiGa2O4/CeO2 nanocomposite with enhanced sonocatalytic activity

A novel direct Z-scheme NiGa₂O₄/CeO₂ nanocomposite was designed and prepared via simple sol-hydrothermal and calcination methods, and its sonocatalytic activity was tested by studying the degradation of a model antimicrobial agent, malachite green (MG), under ultrasonic irradiation. Near complete (96.2%) degradation of MG (at 10 mg/L) could be achieved by the NiGa₂O₄/CeO₂ nanocomposite (at 1.0 g/L) after ultrasonic irradiation (40 kHz, 300 W) for 60 min at 25 °C. Under the same conditions, only 51.2 and 72.0% of the MG degraded in the presence of NiGa₂O₄ and CeO₂ (at 1.0 g/L), respectively. These results demonstrate that the direct Z-scheme NiGa₂O₄/CeO₂ nanocomposite has excellent sonocatalytic activity, which is attributed to the matching band-gaps between NiGa₂O₄ and CeO₂. The sonocatalytic activity of NiGa₂O₄/CeO₂ nanocomposite decreased by 17% after four cycles of reuse, which is indicative of relatively good reusability. Scavenging experiments revealed that sonocatalytic degradation of MG results from the combined action of hydroxyl radicals (OH) and holes (h⁺), with the latter having a greater contribution. The pathways and mechanism of MG degradation were proposed based on the degradation intermediates detected. The results demonstrate that the prepared direct Z-scheme NiGa₂O₄/CeO₂ nanocomposite worked as designed and exhibited high and stable sonocatalytic activity during MG degradation, and could thus serve as a promising candidate in sonocatalytic treatment of other organic pollutants in wastewaters. The findings also provide new insights on the mechanism of sonocatalytic degradation and the design of efficient Z-scheme sonocatalysts.