Unraveling the Plasmonic Effect of Au in Promoting Photocatalytic H₂ Generation and Organic Synthesis

Incorporating plasmonic nanostructures into photocatalysts significantly enhances catalytic efficiency due to plasmonic effects. In this study, we successfully developed a heterojunction between organic semiconductor zinc porphyrin (Zn-TCPP) and colloidal gold (Au) nanoparticles connected via Au–O bonds. The formation of Au–O bonds between Zn-TCPP and Au facilitates charge transfer efficiency by reducing the Schottky barrier at the heterojunction interface. Finite-difference time-domain simulations, in situ XPS measurements, and infrared thermal imaging confirm that the strong localized surface plasmon resonance effect of Au enhances the local electric field and photothermal effect, promoting the separation of electron–hole pairs in the Zn-TCPP/Au sample and improving the reaction kinetics. The optimal Zn-TCPP/Au-2% composite demonstrates an impressive H2 generation rate of 1610 μmol·g–1·h–1, which is 2.7 and 8.6 times greater than the Zn-TCPP and TCPP samples, respectively. Additionally, the Zn-TCPP/Au-2% composite shows high efficiency in the C–N coupling of benzylamine to imine, achieving a yield of 45.1 mmol·g–1 in 24 h. This study provides a comprehensive understanding of how the plasmonic effect of Au enhances the activity of organic semiconductor photocatalysts.