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 zeolitic imidazolate framework-67 (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.