First-Principles Study of Formaldehyde Adsorption on TiO₂ Rutile (110) and Anatase (001) Surfaces

Abstract

This study investigated adsorption and reactions of formaldehyde (HCHO) on TiO2 rutile (110) and anatase (001) surfaces by first-principles calculation. The structure, vibrational frequencies, and electronic properties of the interaction system are studied to investigate the adsorption mechanisms of HCHO on TiO2 surfaces. It is found that HCHO can chemically adsorb on all surfaces to form into a dioxymethylene structure with O of HCHO bonding to a coordinatively unsaturated surface Ti atom (Ti4C or Ti5C) and C bonding to a surface O2C. The anatase (001) surface is found to be more active in HCHO adsorption with lower adsorption energy and larger charge transfer. In addition, the (1 × 4) reconstructed anatase (001) surfaces are found to have higher adsorption ability and more stable surface properties than that on (1 × 1) unreconstructed ones. These findings indicate that the (001) surface holds the potential for the improvement of sensitivity to reductive HCHO gas, in which the (1 × 4) reconstructed surface may play an important role for further improving gas-sensing properties of TiO2-based sensors while keeping the stability of them.

Adsorption and oxidation of oxalic acid on anatase TiO2 (001) surface: A density functional theory study

“…The corresponding Ti 5c AO 2c bond length is elongated from 2.253 Å to 2.577 Å. The broken Ti 5c AO 2c bonds are also observed after the adsorption of other small molecules on the anatase (0 0 1) surface, such as methanol, formaldehyde, formic acid, nitric oxide, and water [16,17,33,34]. As a comparison, in the most stable DB4 configuration, both of the structures of the anatase (0 0 1) surface and the adsorbate are slightly relaxed after the adsorption (see Fig.…”

“…Based on the studies by Gong et al about the adsorption properties of formic acid on the clean anatase (0 0 1) surface, they proposed that the clean anatase (0 0 1) surface places a key role in the reactivity of anatase TiO 2 nanoparticles degradation performance [16]. The strong adsorption of formaldehyde molecules on the bare anatase (0 0 1) surface has been demonstrated by using density functional theory (DFT) calculations by Liu et al [17]. Recently, we have measured the adsorption properties and intrinsic degradation kinetics of oxalic acid on the photoanode mainly exposed by {0 0 1} facets using PEC techniques [18].…”

Photoinduced Decomposition of Formaldehyde on a TiO2(110) Surface, Assisted by Bridge-Bonded Oxygen Atoms

“…Taking into account additional TPD traces ( Figure S1, Supporting Information), the 360 K shoulder is also assigned to CH 2 O. Recent theoretical results 34,35 show that a dioxymethylene structure involving CH 2 Two additional new desorption features at 486 and 580 K grow in the m/z = 29 TPD spectrum with increasing irradiation times. TPD traces were collected at a variety of m/z ratios to assign the new features ( Figure S1 in Supporting Information).…”

Tracking Site-Specific C–C Coupling of Formaldehyde Molecules on Rutile TiO2(110)

“…4 However, the adsorption geometry, the role of defects, and the reaction intermediates of formaldehyde on the most studied reducible oxide surface, rutile TiO 2 (110), are not understood, mainly because the experimental and theoretical results are not in agreement. 9,13,20,21 Experimentally, temperature programed desorption (TPD) results show that formaldehyde adsorbs more strongly on bridge-bonded oxygen vacancy (V O ) sites and undergoes the carbon-carbon bond coupling to produce C 2 H 4 via a diolate intermediate (−OCH 2 CH 2 O−) identified by high resolution electron energy loss spectroscopy (HREELS). 8 The formation of C 2 H 4 is further supported by other groups via X-ray photoemission spectroscopy (XPS) and TPD studies.…”