Photocatalytic CO₂ Reduction Using Ti₃C₂X_y (X = Oxo, OH, F, or Cl) MXene–ZrO₂: Structure, Electron Transmission, and the Stability

Abstract

CO 2 photoreduction using a semiconductor-based photocatalyst is a promising option for completing a new carbon− neutral cycle. The short lifetime of charges generated owing to light energy is one of the most critical problems in further improving the performance of semiconductor-based photocatalysts. This study shows the structure, electron transmission, and stability of Ti 3 C 2 X y (X = oxo, OH, F, or Cl) MXene combined with a ZrO 2 photocatalyst. Using H 2 as a reductant, the photocatalytic CO formation rate increased by 6.6 times to 4.6 μmol h −1 g cat −1 using MXene (3.0 wt %)−ZrO 2 compared to that using ZrO 2 , and the catalytic route was confirmed using 13 CO 2 to form 13 CO. In clear contrast, using H 2 O (gas) as a reductant, CH 4 was formed as the major product using Ti 3 C 2 X y MXene (5.0 wt %)−ZrO 2 at the rate of 3.9 μmol h −1 g cat −1. Using 13 CO 2 and H 2 O, 12 CH 4 , 12 C 2 H 6 , and 12 C 3 H 8 were formed besides H 2 12 CO, demonstrating that the C source was the partial decomposition and hydrogenation of Ti 3 C 2 X y . Using the atomic force and high-resolution electron microscopies, 1.6 nm thick Ti 3 C 2 X y MXene sheets were observed, suggesting ∼3 stacked layers that are consistent with the Ti−C and Ti•••Ti interatomic distances of 0.218 and 0.301 nm, respectively, forming a [Ti 6 C] octahedral coordination, and the major component as the X ligand was suggested to be F and OH/oxo, with the temperature increasing by 116 K or higher owing to the absorbed light energy, all based on the extended X-ray absorption fine structure analysis.

Visible-Light-Driven Reduction of CO2 to CO with Highly Active and Selective Earth-Abundant Metal Porphyrin-Conjugated Organic Polymers

“…Photosynthesis by plants can mitigate this phenomenon by converting CO 2 and water into oxygen and carbohydrates under sunlight irradiation, inspiring researchers to explore simulated plant photosynthesis and develop artificial photocatalytic systems that convert CO 2 into economically valuable chemical products, such as CH 4 , CO, and CH 3 OH. − The most important part of this work is the construction of photocatalysts. Although some inorganic oxides , or some organic semiconductor materials (MOFs, COFs, COPs, etc. ), have been reported for photocatalytic reduction of CO 2 , , complexes of noble metals such as Ru, Ir, Rh, and Re are usually added as visible-light photosensitizers to achieve higher catalytic yields. − But in fact, these materials containing noble metals are difficult to promote their large-scale commercial application due to the high cost and scarcity.…”