CuO/carbon spheres/g-C3N4 with 3D hierarchical porous structure and functional carbon bridge for efficient CO2 adsorption and photocatalytic reduction

Abstract

Utilizing photocatalysis to reduce CO₂ into value-added products is a promising and sustainable pathway. This study reports the fabrication of a low-cost CuO/carbon spheres/g-C₃N₄ composite material without the use of precious metals, featuring a p-n heterojunction between CuO and g-C₃N₄ interconnected by a conductive carbon bridge. The optimal sample has suitable CO₂ adsorption capacity (1.4 mmol/g at 1 bar, 25 °C) and exceptional CO₂ photocatalytic performance. The optimal sample achieves CO and CH₄ production yields of 110.95 and 9.9 μmol/g h⁻¹, respectively, with 73.7% CO selectivity. Photoelectrochemical tests reveal that the CuO/g-C₃N₄ heterojunction facilitates rapid electron transfer via the carbon medium, achieving effective electrons(e⁻)-holes(h⁺) separation. In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (in-situ DRIFTS) analysis and Density Functional Theory (DFT) calculations collaboratively verify the efficient reaction pathway via key intermediates (COOH*, CHO*, CH₂O*, and CH₃O*) and elucidate the electronic structure driving the enhanced charge dynamics. Furthermore, property-performance correlation analysis indicates that the charge separation efficiency is the main performance driving factor. A life cycle assessment (LCA) demonstrates that avoiding the use of precious metals during catalyst preparation leads to a significant reduction in the environmental footprint of CuO/carbon spheres/g-C₃N₄. The main environmental impact comes from electricity consumption during production. This work provides a sustainable blueprint for designing efficient photocatalysts by integrating interfacial engineering with mechanistic understanding for solar-driven CO₂ valorization.