Enhancing photocatalytic CO2 reduction with TiO2-based materials: Strategies, mechanisms, challenges, and perspectives

Abstract

The concentration of atmospheric CO₂ has exceeded 400 ppm, surpassing its natural variability and raising concerns about uncontrollable shifts in the carbon cycle, leading to significant climate and environmental impacts. A promising method to balance carbon levels and mitigate atmospheric CO₂ rise is through photocatalytic CO₂ reduction. Titanium dioxide (TiO₂), renowned for its affordability, stability, availability, and eco-friendliness, stands out as an exemplary catalyst in photocatalytic CO₂ reduction. Various strategies have been proposed to modify TiO₂ for photocatalytic CO₂ reduction and improve catalytic activity and product selectivity. However, few studies have systematically summarized these strategies and analyzed their advantages, disadvantages, and current progress. Here, we comprehensively review recent advancements in TiO₂ engineering, focusing on crystal engineering, interface design, and reactive site construction to enhance photocatalytic efficiency and product selectivity. We discuss how modifications in TiO₂'s optical characteristics, carrier migration, and active site design have led to varied and selective CO₂ reduction products. These enhancements are thoroughly analyzed through experimental data and theoretical calculations. Additionally, we identify current challenges and suggest future research directions, emphasizing the role of TiO₂-based materials in understanding photocatalytic CO₂ reduction mechanisms and in designing effective catalysts. This review is expected to contribute to the global pursuit of carbon neutrality by providing foundational insights into the mechanisms of photocatalytic CO₂ reduction with TiO₂-based materials and guiding the development of efficient photocatalysts.

Graphical abstract

Fig. 1

The modification strategies of TiO₂ in this review.

Fig. 2

a, Schematic of the mechanism of photocatalytic CO₂ reduction on TiO₂. b, Suitable reduction potential (vs. NHE at pH = 7) and corresponding products.

Fig. 3

a, The occupied state diagram above the valence band of TiO₂ [104]. b, Photocatalytic methanol generation via TiO₂ and P-TiO₂ samples. c, Plots of (ahv)^1/2 versus the photon energy (hv). d, Absorption spectra of the P-TiO₂ samples. Adapted with permission from Ref. [104]. Copyright 2022, Multidisciplinary Digital Publishing Institute. Adapted with permission from Ref. [105]. Copyright 2016, Elsevier B.V.

Fig. 4

UV-vis absorption spectra (a), photocurrent (b), fluorescence spectra (c), electrochemical impedance spectroscopy (d), CH₄ yield (e), and CH₄ selectivity (f) of TiO₂ and Mo-TiO₂ samples. Adapted with permission from Ref. [120] Copyright 2020, Elsevier B.V.

Fig. 5

Three types of band alignments for n-n heterojunction: a, straddling gap (Type-Ⅰ); b, staggered gap (Type-Ⅱ); c, broken gap (Type-Ⅲ).

Fig. 6

a, Photocatalytic CO₂ reduction activities of all samples. b, Repeated experiments of TiO₂/ZnIn₂S₄-10. c, Photocurrent and electrochemical impedance spectra. d, Mechanism illustration of CO₂ reduction of TiO₂/ZnIn₂S₄. Adapted with permission from Ref. [154]. Copyright 2022, Elsevier B.V.

Fig. 7

a, EDS mapping of PtRu/TiO₂. b, Photocatalytic CO₂ reduction to CH₄ rates of samples. c, Schematic illustration of photocatalytic CO₂ reduction via PtRu/TiO₂. Adapted with permission from Ref. [207]. Copyright 2018, Elsevier B.V.

Fig. 8

a, TEM image of TOH. b, CO₂ adsorption isotherms on TOH and TON. c, CO₂ adsorption isotherms on TiO₂ and TiO₂/AC. d, CO₂ adsorption isotherms on TiO₂ and TiO₂/WO₄-X. Adapted with permission from Refs. [[223], [224], [225]]. Copyright 2021, 2018, 2019, Elsevier B.V.

Fig. 9

Schematic diagram of the “typical Lewis acid-base chemistry” and “Frustrated Lewis pairs chemistry”.

Fig. 10

a, CO₂-TPD of TiO_2−x and TiO₂-A. b, Schematic illustration of CO₂ reduction via TiO_2−x. c–d, Photocatalytic CO₂ reduction to CO activities via TiO_2−x(c) and TiO₂-A (d) samples. Adapted with permission from Ref. [71]. Copyright 2022, Elsevier B.V.