Recent Advances in Quantum Dots for Photocatalytic CO2 Reduction: A Mini-Review

Abstract

Solar energy-driven carbon dioxide (CO₂) reduction to valuable solar fuels/chemicals (e.g., methane, ethanol, and carbon monoxide) using particulate photocatalysts is regarded as one of the promising and effective approaches to deal with energy scarcity and global warming. The growth of nanotechnology plays an eminent role in improving CO₂ reduction (CO₂R) efficiencies by means of offering opportunities to tailor the morphology of photocatalysts at a nanoscale regime to achieve enhanced surface reactivity, solar light absorption, and charge separation, which are decisive factors for high CO₂R efficiency. Notably, quantum dots (QDs), tiny pieces of semiconductors with sizes below 20 nm, offering a myriad of advantages including maximum surface atoms, very short charge migration lengths, size-dependent energy band positions, multiple exciton generation effect, and unique optical properties, have recently become a rising star in the CO₂R application. In this review, we briefly summarized the progress so far achieved in QD-assisted CO₂ photoreduction, highlighting the advantages of QDs prepared with diverse chemical compositions such as metal oxides, metal chalcogenides, carbon, metal halide perovskites, and MXenes.

Keywords: CO2 reduction; MXene; carbon quantum dot; metal oxide; perovskite; photocatalyst; quantum dots; transition metal chalcogenide.

FIGURE 1

Schematic illustration of the (A) photocatalytic CO₂ conversion method, (B) CO₂ conversion by semiconducting photocatalyst, (C) density of states modification under different degrees of quantum confinement, and (D) the advantages of the QDs for the photocatalytic reduction of CO₂.

FIGURE 2

TEM images of CsPbBr₃ QDs with particle sizes of (A) 3.8 nm, (B) 6.1 nm, (C) 8.5 nm, and (D) 11.6 nm (inset crystal structures). Photocatalytic CO₂R for QDs with (E) 8.5 nm CsPbBr₃ QDs and (F) CsPbBr₃ QDs of different sizes (reproduced with permission from (Hou et al., 2017)). (G) Schematic illustration for synthesis of Ti₃C₂ QDs and Ti₃C₂ QDs/Cu₂O NWs/Cu heterostructure, FE-SEM images of (H) Cu₂O NWs/Cu, (i) Ti₃C₂ QDs/Cu₂O NWs/Cu heterostructures, (J) CH₃OH yield as a function of time, and (K) energy level diagram of Ti₃C₂ QDs/Cu₂O NWs/Cu and Ti₃C₂ sheets/Cu₂O NWs/Cu heterostructures (reproduced with permission from (Zeng et al., 2019)).