Size-dependent photocatalytic reduction of CO2 with PbS quantum dot sensitized TiO2 heterostructured photocatalysts

Abstract

The photocatalytic reduction of CO₂ to value-added chemicals, such as CH₄, is a promising carbon management approach which can generate revenue from chemical sales to offset the cost of implementing CO₂ capture technologies. To make photocatalytic conversion approaches efficient, economically practical, and industrially scalable, catalysts capable of utilizing visible and near infrared (IR) photons need to be developed. Here we investigate the sensitization of TiO₂ catalysts using PbS quantum dots (QDs) which lead to the size dependent photocatalytic reduction of CO₂ at frequencies ranging from the violet to the orange-red edge of the electromagnetic spectrum (λ ∼ 420 to 610 nm). Under broad band illumination (UV- NIR), the PbS QDs enhance CO₂ photoreduction rates with TiO₂ by a factor of ∼5 in comparison to unsensitized photocatalysts. X-ray photoelectron spectroscopy (XPS) is used to investigate the deactivation mechanism of the QD sensitizers after prolonged photoexcitation. The synthesis, characterization, and catalytic testing of these PbS sensitized TiO₂ heterostructures will aid the development of more robust, visible light active photocatalysts for carbon management applications.