ZIF-67-derived NiCo2O4 hollow nanocages coupled with g-C3N4 nanosheets as Z-scheme photocatalysts for enhancing CO2 reduction

Photocatalytic CO 2 reduction technology plays a significant role in the energy and environmental sectors, highlighting the necessity for developing high-efficiency and stable catalysts. In this study, a novel photocatalyst, x NiCo 2 O 4 /CN ( x  = 1, 3, and 5 wt%), was synthesized by depositing zeolitic imidazolate framework-67 (ZIF-67)-derived nickel cobaltate (NiCo 2 O 4 ) hollow nanocages onto porous graphitic carbon nitride ( g -C 3 N 4 , CN) nanosheets for photocatalytic CO 2 reduction. Under visible light irradiation, the resulting 3NiCo 2 O 4 /CN photocatalyst demonstrated exceptional CO yields of up to 2879.5 μmol g −1  h −1 , surpassing those of NiCo 2 O 4 and CN alone by factors of 3.3 and 11.6, respectively. The introduction of hollow NiCo 2 O 4 nanocages increased the specific surface area of the material and enhanced the number of active sites, while strengthening visible light absorption. The creation of a built-in electric field, induced by the Fermi level difference between the two materials, was confirmed through ultraviolet photoelectron spectroscopy (UPS) characterization. This resulted in the formation of a Z-scheme heterojunction, significantly enhancing the separation and migration of photogenerated charge carriers. Notably, 3NiCo 2 O 4 /CN exhibits excellent stability during long-term photocatalytic reactions, ensuring reliable performance for practical applications. This study offers novel insights and methodologies for developing efficient photocatalytic CO 2 reduction catalysts.