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

Abstract

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.