All-solid-state Z-scheme 3,4-dihydroxybenzaldehyde-functionalized Ga2O3/graphitic carbon nitride photocatalyst with aromatic rings as electron mediators for visible-light photocatalytic nitrogen fixation

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.