Two-dimensional titanium carbide (MXene)-supported Pt3Ti intermetallic compound catalysts for efficient room-temperature oxidative removal of gaseous formaldehyde

The potential of reactive metal–support interactions has been investigated using platinum (Pt) and a two-dimensional titanium carbide (Ti3C2 [MXene]) support to achieve the full conversion of formaldehyde (FA: XFA) into carbon dioxide (CO2) at room temperature (RT) through the formation of a Pt3Ti intermetallic compound. The RT steady-state oxidation reaction rate (mol/g/h) of FA increased in the following order: 2% Pt/Ti3C2 (0.020) < 0.1% Pt/Ti3C2-R (0.054) < 1% Pt/Ti3C2-R (0.058) < 2% Pt/Ti3C2-R (0.061: turnover frequency of approximately 60 mmolFA/molO/s). The Pt3Ti formed in situ during reduction pre-treatment (R) enhanced catalytic activity, and 2% Pt/Ti3C2-R achieved significant resistance to moisture by maintaining 100% XFA at a relative humidity of 0%–90%. In situ diffuse reflectance infrared Fourier-transform spectroscopy revealed the formation of dioxymethylene, formate, and carbon monoxide as the reaction intermediates of FA oxidation. According to the density functional theory simulations, the carbonyl bond (C=O) of FA appears to be activated through chemisorption on Pt3Ti (adsorption of oxygen and carbon atoms (in C=O) on the Pt and titanium sites of Pt3Ti, respectively) to generate CO2 through reaction with active oxygen species formed by the decomposition of molecular oxygen on the Pt/Ti sites. In terms of the normalized reaction rate, 0.1 Pt/Ti3C2-R (0.55 mol/g/h [bulk Pt, wt.%]–1) appears to be one of the best-performing Pt catalysts reported for FA oxidation at RT.