Boosting Photocatalytic N-2 Fixation on N-Defect g-C3N4/WO3: the Synergistic Effects of Nitrogen Vacancy and Z-Scheme Heterojunction

Photocatalytic nitrogen fixation is a promising strategy for ammonia synthesis under mild conditions by using solar energy, but N-2 activation remains a great challenge. Herein, we demonstrate that a Z-scheme g-C3N4/WO3 heterojunction possessing abundant nitrogen vacancies exhibits the highly enhanced activity for photocatalytic N-2 fixation through efficient nitrogen molecular activation compared with pristine NVs-g-C3N4 and WO3 photocatalysts. The construction of the internal electric field induced by Z-scheme NVs-g-C3N4/WO3 heterojunction allows a rapid charge carrier separation and simultaneously maintains the powerful redox ability of photogenerated charge carriers, defined by the covalent C-O bond. Moreover, nitrogen vacancy plays a crucial role in the adsorption/activation of N-2, which substantially facilitates the hydrogenation to generate NH3. According to experimental and theoretical investigations, photocatalytic N-2 fixation on NVs-g-C3N4/WO3 composites is proposed to be energetically favorable in the alternating pathway. This study offers an alternative way for the design of efficient photocatalysts for photocatalytic N-2 fixation.