Photocatalytic NADH Regeneration Employing Au-Pd Core-Shell Nanoparticles: Plasmonic Modulation of Underlying Reaction Kinetics

Integrating catalytically active metals (Pt, Pd, Ru, etc.) with plasmonic metals (Au, Ag, Cu, etc.) allows to combine the merits of both and achieve efficient heterogeneous catalysis. Here, we have grown anisotropic Pd over Au nanocubes (NCs) using a seed-mediated method to engineer Au-Pd core-shell nanoparticles (Au-Pd CS NPs). The Au-Pd CS NPs showed a high conversion rate for nicotinamide adenine dinucleotide hydrogen (NADH) regeneration under visible light irradiation, while their activity in dark conditions remained limited. Moreover, only Au NCs or Pd seed nanoparticles under the same reaction conditions show no significant NADH regeneration, highlighting the synergistic effect of the plasmonic core and catalytic shell. To distinguish if the plasmonic enhancement with Au-Pd CS NPs resulted from hot charge carrier generation or plasmonic heating, we have (i) carried out the reaction under isothermal conditions and (ii) performed beta-NAD(+) concentration-dependent kinetic studies to know the underlying mechanism in dark and light conditions, which should have been the same had the enhancement been a result of a heating effect. In beta-NAD(+) concentration-dependent studies, it was discovered that the dark reaction rate reduced with increasing concentrations, while the light reaction rate became saturated. These observations follow the competitive and noncompetitive bimolecular Langmuir-Hinshelwood (L-H) model. The transition from competitive to non-competitive reaction kinetics has been explained by considering the energetic charge carrier generation on the catalyst surface with light illumination. Our study expands the current domain of catalysts involved in the beta-NAD(+) reduction and provides a mechanistic insight for plasmondriven catalysis, which is necessary to improve catalytic efficiency.

Automated summary

This study demonstrates the synthesis of efficient Au-Pd core-shell nanoparticles that combine catalytic activity with plasmonic enhancement. The Au-Pd CS NPs showed high conversion rates for NADH regeneration under visible light irradiation. The mechanism of plasmonic enhancement was investigated through isothermal reactions and kinetic studies, revealing the energetic charge carrier generation as the driving force. This research expands the understanding of plasmon-driven catalysis and provides insights for improving catalytic efficiency.