Modulation of the Reduction Potential of TiO_2–x by Fluorination for Efficient and Selective CH₄ Generation from CO₂ Photoreduction

Abstract

Photocatalytic reduction of CO holds great promises for addressing both the environmental and energy issues that are facing the modern society. The major challenge of CO photoreduction into fuels such as methane or methanol is the low yield and poor selectivity. Here, we report an effective strategy to enhance the reduction potential of photoexcited electrons by fluorination of mesoporous single crystals of reduced TiO. Density functional theory calculations and photoelectricity tests indicate that the Ti impurity level is upswept by fluorination, owing to the built-in electric field constructed by the substitutional F that replaces surface oxygen vacancies, which leads to the enhanced reduction potential of photoexcited electrons. As a result, the fluorination of the reduced TiO dramatically increases the CH production yield by 13 times from 0.125 to 1.63 μmol/g·h under solar light illumination with the CH selectivity being improved from 25.7% to 85.8%. Our finding provides a metal-free strategy for the selective CH generation from CO photoreduction.

Ultrathin SiC Nanosheets with High Reduction Potential for Improved CH4 Generation from Photocatalytic Reduction of CO2

“…Photocatalytic CO 2 reduction performance was evaluated in the presence of H 2 O vapor, involving a gas‐solid heterogeneous reaction in our reaction system. CO and CH 4 were detected as the main products(Figure a), in accordance with previous reports using similar method ,. The generation rates of CO and CH 4 together with CH 4 selectivity are summarized in Figure b.…”

“…Thermodynamically speaking, a semiconductor with more negative conduction band (CB) potential possesses a higher driving force to transfer photogenerated electrons, which is beneficial for deep reduction of CO 2 into CH 4 . For example, Xing et al . recently demonstrated that the yield and selectivity of CH 4 generation from photoreduction of CO 2 were dramatically improved by modulation of the reduction potential of TiO 2‐x .…”

Strategies for Designing Nanoparticles for Electro‐ and Photocatalytic CO2 Reduction

“…It has been demonstrated that surface‐attached halogen atoms effectively trap photoinduced holes and elongate the charge separation lifetime, resulting in high photocatalytic efficiency . In addition, halogenation slightly up‐shifts the reduction potential of semiconductors . It was verified by DFT calculation that surface F atoms replaced oxygen vacancies and established internal electric fields in TiO 2− x , leading to an upsweep of Ti 3+ impurity level.…”

“…Yin et al. demonstrated that the fluorination of TiO 2− x nanoparticles dramatically increased the efficiency by 13 times and the selectivity from 25.7 % to 85.8 % for CH 4 production …”

Surface Modification on Pd‐TiO2 Hybrid Nanostructures towards Highly Efficient H2 Production from Catalytic Formic Acid Decomposition

“…[9][10][11] For instance, various foreign atoms have been introduced into metal-containing heterogeneousc atalysts to increaset he selectivity in catalytic reactions. [9][10][11] For instance, various foreign atoms have been introduced into metal-containing heterogeneousc atalysts to increaset he selectivity in catalytic reactions.…”