An all-solid-state Z-scheme heterojunction-structured photocatalyst, 3,4-dihydroxybenzaldehyde-functionalized Ga 2 O 3 /graphitic carbon nitride (Ga 2 O 3 -DBD/g-C 3 N 4 ), was synthesized using a facile post-grafting strategy via Schiff base chemistry. It was proposed for the first time that aromatic rings served as electron mediators in the Z-scheme photocatalytic system. In addition, the aromatic rings were conducive to the formation of a well-developed combined interface between Ga 2 O 3 -DBD and g-C 3 N 4 , greatly improving the separation of electrons and holes. The Ga 2 O 3 -DBD/g-C 3 N 4 exhibited a wide absorption range, high charge-separation efficiency and high redox potential, thus enhancing its activity and stability for visible-light photocatalytic nitrogen fixation. The reaction mechanism was demonstrated to be that O 2 was first reduced to H 2 O 2 , which was further oxidized to OH; then, OH reacted with methanol to form CO 2 − , which facilitated the reduction of N 2 to NH 3 . This study demonstrates a simple and cost-effective approach to synthesize all-solid-state Z-scheme photocatalytic system using the aromatic rings, and this system exhibits great potential for practical applications of visible-light photocatalytic nitrogen fixation.
Qijie Yu,Jiulin Hu,Xianhui Nie,Yuhan Zeng,Chilin Li
Fluoride-based solid electrolytes (SEs) have emerged as a promising component for high-energy-density rechargeable solid-state batteries (SSBs) in view of their wide electrochemical window, high air stability, and interface compatibility, but they still face the challenge of low ion conductivity and the lack of a desired structure for sodium metal SSBs. Here, we report a sodium-rich heterostructure fluoride SE, Na3GaF6–Ga2O3–NaCl (NGFOC-G), synthesized via in situ oxidation of liquid metal gallium and in situ chlorination using low-melting GaCl3. The distinctive features of NGFOC-G include single-crystal Na3GaF6 domains within an open-framework structure, composite interface decoration of Ga2O3 and NaCl with a concentration gradient, exceptional air stability, and high electrochemical oxidation stability. By leveraging the penetration of gallium at NaF grain boundaries and the in situ self-oxidation to form Ga2O3 nanodomains, the solid-phase reaction kinetics of NaF and GaF3 is activated for facilitating the synthesis of main component Na3GaF6. The introduction of a small amount of a chlorine source during synthesis further softens and modifies the boundaries of Na3GaF6 along with Ga2O3. Benefiting from the enhanced interface ion transport, the optimized NGFOC-G exhibits an ionic conductivity up to 10–4 S/cm at 40 °C, which is the highest level reported among fluoride-based sodium-ion SEs. This SE demonstrates a “self-protection” mechanism, where the formation of a high Young’s modulus transition layer rich in NaF and Na2O under electrochemical driving prevents the dendrite growth of sodium metal. The corresponding Na/Na symmetric cells show minimal voltage hysteresis and stable cycling performance for at least 1000 h. The Na/NGFOC-G/Na3V2(PO4)3 cell demonstrates stable capacity release around 100 mAh/g at room temperature. The Na/NGFOC-G/FeF3 cell delivers a high capacity of 461 mAh/g with an excellent stability of conversion reaction cycling.
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