Copper and platinum dual-single-atoms supported on crystalline graphitic carbon nitride for enhanced photocatalytic CO2 reduction

Single-atom Pt catalysts are designed to promote efficient atom utilization, whereas effective decrease of Pt loading and improvement of photocatalytic activity in monoatomic Pt-deposited systems is still ongoing. Atomically dispersed metal species in crystalline carbon nitride are still challenging owing to their high crystallization and structural stability. In this study, we developed a novel single-atomic Pt-Cu catalyst for reducing noble metal loading by combining Pt with earth-abundant Cu atoms and enhancing photocatalytic CO2 reduction. N-vacancy-rich crystalline carbon nitride was used as a fine-tuning ligand for isolated Pt-Cu atom dispersion based on its accessible functional N vacancies as the seeded centers. The synthesized dimetal Pt-Cu atoms on crystalline carbon nitride (PtCu-crCN) exhibited high selectivity and activity for CO2 conversion without the addition of any cocatalyst or sacrificial agent. In particular, we demonstrated that the diatomic Pt-Cu exhibited high mass activity with only 0.32 wt% Pt loading and showed excellent photocatalytic selectivity toward CH4 generation. The mechanism of CO2 photoreduction for PtCu-crCN was proposed based on the observations and analysis of aberration-corrected high-angle annular dark-field scanning transmission electron microscopy images, in situ irradiated X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The findings of this work provide insights for abrogating specific bifunctional atomic metal sites in noble metal-based photocatalysts by reducing noble metal loading and maximizing their effective mass activity.