Zif-67-Derived Nico2o4 Hollow Nanocages Coupled with G-C3n4 Nanosheets as Z-Scheme Photocatalysts for Enhancing Co2 Reduction

Abstract

Photocatalytic CO2 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, xNiCo2O4/CN (x = 1, 3, and 5 wt.%), was synthesized by depositing ZIF-67-derived nickel cobaltate (NiCo2O4) hollow nanocages onto porous graphitic carbon nitride (g-C3N4, CN) nanosheets for photocatalytic CO2 reduction. Under visible light irradiation, the resulting 3NiCo2O4/CN photocatalyst demonstrated exceptional CO yields of up to 2879.5 μmol g-1 h-1, surpassing those of NiCo2O4 and CN alone by factors of 3.3 and 11.6, respectively. The introduction of hollow NiCo2O4 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, 3NiCo2O4/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 CO2 reduction catalysts.

Keywords: Photocatalytic CO2 reduction, nickel cobaltate, graphitic carbon nitride, Z-scheme heterojunction