SPR-enhanced photocatalytic CO2 reduction over CuOx/N-vacancy-rich g-C3N4 heterojunction: Unraveling the synergistic roles of defect engineering and charge transfer pathways

Constructing efficient photocatalysts for CO2 reduction is challenging due to the inefficient CO2 activation and rapid photoinduced charge recombination. In this work, a ternary Cu/Cu2O/N-vacancy-rich g-C3N4 (CuOx/NVCN) heterostructure photocatalyst is rationally designed and synthesized via an ice-assisted photoreduction method. The introduction of nitrogen vacancies (NVs) into the g-C3N4 framework serves as active sites for enhanced CO2 adsorption and activation. The construction of an S-scheme heterojunction between Cu2O and creates a built-in electric field that drives the efficient spatial separation of photogenerated charge carriers while preserving their strong redox potentials. Furthermore, the incorporation of plasmonic Cu nanoparticles extends light absorption via the surface plasmon resonance (SPR) effect and provides an additional pathway for hot electron injection. This multi-component system establishes a synergistic electron transfer highway and accelerates the generation and transformation of key intermediates. Consequently, the optimized CuOx/NVCN catalyst achieves a remarkably enhanced CO production rate of 6.13 μmol g−1 h−1, which is 4.6 times that of pristine g-C3N4. This work underscores the profound potential of coupling defect engineering, S-scheme heterojunctions, and plasmonic effects for advanced solar fuel production.