Synergistic effect of modified pore and heterojunction of MOF-derived α-Fe2O3/ZnO for superior photocatalytic degradation of methylene blue.

Mesoporous heterojunction MOF-derived α-Fe2O3/ZnO composites were prepared by a simple calcination of α-Fe2O3/ZIF-8 as a sacrificial template. The optical properties confirm that coupling of both the modified pore and the n-n heterojunction effectively reduces the possibility of photoinduced charge carrier recombination under irradiation. The mesoporous Fe(25)ZnO with 25% loading of α-Fe2O3 exhibited the best performance in MB degradation, up to ∼100% after 150 minutes irradiation, higher than that of pristine ZnO and α-Fe2O3. Furthermore, after three cycles reusability, mesoporous Fe(25)ZnO still showed an excellent stability performance of up to 95.42% for degradation of MB. The proposed photocatalytic mechanism of mesoporous Fe(25)ZnO for the degradation of MB corresponds to the n-n heterojunction system. This study provides a valuable reference for preparing mesoporous MOF-derived metal oxides with an n-n heterojunction system to enhance MB photodegradation.

Modulating the Active Sites of Oxygen-Deficient TiO2 by Copper Loading for Enhanced Electrocatalytic Nitrogen Reduction to Ammonia.

The electrocatalytic nitrogen reduction reaction (NRR) provides a sustainable route for NH3 synthesis. However, the process is plagued by the strong NN triple bond and high reaction barrier. Modification of catalyst surface to increase N2 adsorption and activation is crucial. Herein, copper nanoparticles are loaded on the oxygen-deficient TiO2 , which exhibits an enhanced NRR performance with NH3 yield of 13.6 µg mgcat -1 h-1 at -0.5 V versus reversible hydrogen electrode (RHE) and Faradaic efficiency of 17.9% at -0.4 V versus RHE compared to the pristine TiO2 . The enhanced performance is ascribed to the higher electrochemically active surface area, promoted electron transfer, and increased electron density originated from the strong metal-support interaction (SMSI) between Cu nanoparticles and oxygen-deficient TiO2 . The SMSI effect also results in lopsided local charge distribution, which polarizes the adsorbed N2 molecules for better activation. This work provides a facile strategy toward the electrocatalyst design for efficient NRR under ambient conditions.

Unveiling the charge transfer behavior within ZSM-5 and carbon nitride composites for enhanced photocatalytic degradation of methylene blue.

ZSM-5/graphitic carbon nitride (g-C3N4) composites were successfully prepared using a simple solvothermal method. By varying the amount of ZSM-5 and g-C3N4 in the composites, the charge carrier (electrons and holes) transfer within the materials, which contributes to the enhanced photocatalytic performance, was unraveled. The X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM) analysis revealed that more ZSM-5 component leads to a stronger interaction with g-C3N4. The photocatalytic performance test toward methylene blue (MB) degradation shows that more ZSM-5 in the composites is beneficial in enhancing photocatalytic activity. Meanwhile, the impedance electron spectroscopy (EIS) and photoluminescence (PL) analysis revealed that ZSM-5 facilitates the charge carrier transfer of photogenerated electrons and holes from g-C3N4 to the catalyst surface due to its lower charge transfer resistance. During the charge carrier migration, the interface between g-C3N4 and ZSM-5 particles may induce higher resistance for the charge carrier transfer, however after passing through the interface from g-C3N4 to ZSM-5 particles, the charge carrier can be efficiently transferred to the surface, hence suppressing the charge carrier recombination.