Synthesis of synergistic catalysts: integrating defects, SMSI, and plasmonic effects for enhanced photocatalytic CO₂...

This study explores how the strategic material design introduced synergetic coupling of strong metal-support interaction (SMSI) between copper (Cu) nanoparticles and titanium dioxide (TiO₂) loaded on dendritic fibrous nanosilica (DFNS), defects within TiO₂, and localized surface plasmon resonance (LSPR) of Cu. Mechanistic insights were gained using in situ high-energy radiation fluorescence detection X-ray absorption near edge structure (HERFD-XANES) spectroscopy, electron microscopy, and finite-difference time-domain (FDTD) simulations. The introduction of copper nanoparticles onto the TiO₂ surface induces a change in the electronic structure and surface chemistry of TiO₂, due to the electronic interactions between Cu sites and TiO₂ at the interface, inducing SMSI. This resulted in enhancing light absorption, efficient charge transfer, reducing electron-hole recombination and enhancing the overall catalytic efficiency. The activation energy for CO₂ reduction was significantly reduced in light as compared to dark. Control experiments revealed a dominant role of photoexcited hot carriers, alongside photothermal effects, in driving CO₂ reduction, supported by super-linear light intensity dependence and reduced activation energies. The unique interplay of O-vacancy defects, electron-hole separation in TiO₂ and LSPR effects in Cu led to the excellent performance of the DFNS/TiO₂-Cu10 catalyst. The catalyst outperformed the reported photocatalytic systems with a CO production rate of ∼3600 mmol g_Cu ^-1 h^-1 (360 mmol g_cat ^-1 h^-1) with nearly 100% selectivity. A reaction mechanism was proposed based on the intermediates observed using the in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and co-related to the electron transfer pathways to different reactants using HERFD-XANES. The study concluded that the synergistic coupling of Cu LSPR, charge carrier separation via SMSI at the Cu-TiO₂ interface, and O-vacancy defects stabilized by SMSI enhance the photocatalytic CO₂ reduction performance of this hybrid system.