Facile synthesis of TiO2 supported Pd nanoparticles for efficient photocatalytic CO2 reduction to CH4 with H2O

Abstract

Photocatalytic reduction of CO₂ into high value-added products under mild conditions can not only effectively alleviate the greenhouse effect, but also generate valuable fuels such as CH₄. Herein, by loading palladium nanoparticles (Pd NPs) on the surface of TiO₂ nanosheets (NS), the range of light absorption is expanded and the highly active sites are provided, which significantly improve the photocatalytic performance. When the sample with a Pd mass fraction of 3.75 wt% (Pd_NPs/TiO₂–2), the photocatalyst exhibits an exceptional selectivity of 95.29 % towards CH₄ production, with a yield of 28.5 μmol·g⁻¹·h⁻¹ in pure water, surpassing the performance of Pd_NPs/P25 by a factor of 2.39. Pd NPs efficiently widen the light absorption spectrum of TiO₂ via the localized surface plasmon resonance (LSPR) phenomenon, and act as an electron trap, facilitating the segregation and subsequent utilization of charge carriers. Furthermore, Pd NPs can promote the dissociation of water (H₂O), inhibit the competitive reaction of hydrogen evolution, achieving high CH₄ yield and selectivity. Density functional theory (DFT) calculations show that Pd NPs reduce the energy barrier of the rate-limiting step in the CO₂ reduction process, and improve the reaction kinetic performance and CH₄ yield. This research introduces a novel concept for the advancement of highly efficient photocatalysts aimed at CO₂ reduction.