Surface modification of 2-D Ti3C2Tx for the effective capture and elimination of acetaldehyde as a co-catalyst: A theoretical and experimental study

As a newly explored 2-D material with metallic conductivity, Ti3C2 has drawn much attention as co-catalysts for the photocatalytic oxidation (PCO) of indoor air pollutants. Herein, we implement the periodic density functional theory calculations to study the interaction between Ti3C2 and acetaldehyde molecules and Ti atoms in Ti3C2 are identified as the active sites for the capture of acetaldehyde molecules. When fully saturated with surface terminators (Ti3C2T2, T stands for -F, -O and -OH groups), the Ti3C2F2 and Ti3C2O2 have weak affinity to acetaldehyde while Ti3C2(OH)2 could provide moderate adsorption strength by forming H-bonds with acetaldehyde. Creating T vacancies in Ti3C2T2 monolayers through surface modification could effectively improve its affinity to acetaldehyde with the adsorption energy increasing from 0.281, 0.235 and 0.878 to 1.750, 1.830 and 1.960 eV for Ti3C2Fx, Ti3C2Ox and Ti3C2(OH) x, respectively. The positive effect of Ti3C2Tx as a co-catalyst is also verified by constructing Ti3C2Tx-TiO2 composite photocatalysts. The introduction of Ti3C2Tx flakes effectively promote the PCO of acetaldehyde by improving the adsorption of target molecules and accelerate the separation of electron-hole pairs in TiO2. This work provides a promising 2-D Ti3C2Tx material as a co-catalyst for the capture and photocatalytic elimination of indoor air pollutants.