SURFACE-DEPENDENT PATHWAYS FOR FORMALDEHYDE OXIDATION AND REDUCTION ON TIO2(001)

Hicham Idriss, K S KIM, M A BARTEAU

Research output: Contribution to journalArticle

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Abstract

The reactions of formaldehyde on differently prepared surfaces of a TiO2(001) single crystal were investigated by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Surfaces which had been ion-bombarded and annealed at low temperature, up to ca. 650 K, were oxygen deficient and contained Ti cations in lower oxidation states than +4, in addition to Ti4+ cations. TPD after formaldehyde adsorption on these surfaces showed coincident desorption of methanol and formaldehyde in two temperature domains, at ca. 370 K and ca. 550 K. In contrast on fully oxidized surfaces (obtained by annealing at 750 K and above), formaldehyde and methanol desorbed only at ca. 370 K. Formaldehyde reacted on TiO2(001) surfaces via two different routes. The first was direct reduction of formaldehyde to methanol on the reduced surfaces, as evidenced by the presence of methoxide species at 286.3 eV in the C(1s) spectrum at 250 K following formaldehyde adsorption. Part of the formaldehyde was totally decomposed to C(a), H(a), and O(a);H(a) was involve in the reduction of formaldehyde to methanol, C(a) was oxidized to CO and CO2, while O(a) oxidized reduced titanium sites as indicated by the decrease of the XPS Ti(2p3/2) lines corresponding to Ti(x+) (x < 4). The second principal pathway for reaction of formaldehyde involved a Cannizzaro-type reaction and was only observed on fully oxidized surfaces. This reaction was responsible for the coincident formation of methoxide (286.3 eV) and formate (289.5-289.7 eV) species observed by XPS at room temperature.

Original languageEnglish
Pages (from-to)113-127
Number of pages15
JournalSurface Science Reports
Volume262
Issue number1-2
Publication statusPublished - 1 Feb 1992

Keywords

  • SINGLE-CRYSTAL SURFACES
  • FORMIC-ACID
  • SPECTROSCOPIC IDENTIFICATION
  • ZINC-OXIDE
  • PD(111) SURFACE
  • METHANOL
  • ADSORPTION
  • DECOMPOSITION
  • OXYGEN
  • TITANIUM

Cite this

Idriss, H., KIM, K. S., & BARTEAU, M. A. (1992). SURFACE-DEPENDENT PATHWAYS FOR FORMALDEHYDE OXIDATION AND REDUCTION ON TIO2(001). Surface Science Reports, 262(1-2), 113-127.

SURFACE-DEPENDENT PATHWAYS FOR FORMALDEHYDE OXIDATION AND REDUCTION ON TIO2(001). / Idriss, Hicham; KIM, K S ; BARTEAU, M A .

In: Surface Science Reports, Vol. 262, No. 1-2, 01.02.1992, p. 113-127.

Research output: Contribution to journalArticle

Idriss, H, KIM, KS & BARTEAU, MA 1992, 'SURFACE-DEPENDENT PATHWAYS FOR FORMALDEHYDE OXIDATION AND REDUCTION ON TIO2(001)', Surface Science Reports, vol. 262, no. 1-2, pp. 113-127.
Idriss, Hicham ; KIM, K S ; BARTEAU, M A . / SURFACE-DEPENDENT PATHWAYS FOR FORMALDEHYDE OXIDATION AND REDUCTION ON TIO2(001). In: Surface Science Reports. 1992 ; Vol. 262, No. 1-2. pp. 113-127.
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abstract = "The reactions of formaldehyde on differently prepared surfaces of a TiO2(001) single crystal were investigated by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Surfaces which had been ion-bombarded and annealed at low temperature, up to ca. 650 K, were oxygen deficient and contained Ti cations in lower oxidation states than +4, in addition to Ti4+ cations. TPD after formaldehyde adsorption on these surfaces showed coincident desorption of methanol and formaldehyde in two temperature domains, at ca. 370 K and ca. 550 K. In contrast on fully oxidized surfaces (obtained by annealing at 750 K and above), formaldehyde and methanol desorbed only at ca. 370 K. Formaldehyde reacted on TiO2(001) surfaces via two different routes. The first was direct reduction of formaldehyde to methanol on the reduced surfaces, as evidenced by the presence of methoxide species at 286.3 eV in the C(1s) spectrum at 250 K following formaldehyde adsorption. Part of the formaldehyde was totally decomposed to C(a), H(a), and O(a);H(a) was involve in the reduction of formaldehyde to methanol, C(a) was oxidized to CO and CO2, while O(a) oxidized reduced titanium sites as indicated by the decrease of the XPS Ti(2p3/2) lines corresponding to Ti(x+) (x < 4). The second principal pathway for reaction of formaldehyde involved a Cannizzaro-type reaction and was only observed on fully oxidized surfaces. This reaction was responsible for the coincident formation of methoxide (286.3 eV) and formate (289.5-289.7 eV) species observed by XPS at room temperature.",
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T1 - SURFACE-DEPENDENT PATHWAYS FOR FORMALDEHYDE OXIDATION AND REDUCTION ON TIO2(001)

AU - Idriss, Hicham

AU - KIM, K S

AU - BARTEAU, M A

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N2 - The reactions of formaldehyde on differently prepared surfaces of a TiO2(001) single crystal were investigated by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Surfaces which had been ion-bombarded and annealed at low temperature, up to ca. 650 K, were oxygen deficient and contained Ti cations in lower oxidation states than +4, in addition to Ti4+ cations. TPD after formaldehyde adsorption on these surfaces showed coincident desorption of methanol and formaldehyde in two temperature domains, at ca. 370 K and ca. 550 K. In contrast on fully oxidized surfaces (obtained by annealing at 750 K and above), formaldehyde and methanol desorbed only at ca. 370 K. Formaldehyde reacted on TiO2(001) surfaces via two different routes. The first was direct reduction of formaldehyde to methanol on the reduced surfaces, as evidenced by the presence of methoxide species at 286.3 eV in the C(1s) spectrum at 250 K following formaldehyde adsorption. Part of the formaldehyde was totally decomposed to C(a), H(a), and O(a);H(a) was involve in the reduction of formaldehyde to methanol, C(a) was oxidized to CO and CO2, while O(a) oxidized reduced titanium sites as indicated by the decrease of the XPS Ti(2p3/2) lines corresponding to Ti(x+) (x < 4). The second principal pathway for reaction of formaldehyde involved a Cannizzaro-type reaction and was only observed on fully oxidized surfaces. This reaction was responsible for the coincident formation of methoxide (286.3 eV) and formate (289.5-289.7 eV) species observed by XPS at room temperature.

AB - The reactions of formaldehyde on differently prepared surfaces of a TiO2(001) single crystal were investigated by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Surfaces which had been ion-bombarded and annealed at low temperature, up to ca. 650 K, were oxygen deficient and contained Ti cations in lower oxidation states than +4, in addition to Ti4+ cations. TPD after formaldehyde adsorption on these surfaces showed coincident desorption of methanol and formaldehyde in two temperature domains, at ca. 370 K and ca. 550 K. In contrast on fully oxidized surfaces (obtained by annealing at 750 K and above), formaldehyde and methanol desorbed only at ca. 370 K. Formaldehyde reacted on TiO2(001) surfaces via two different routes. The first was direct reduction of formaldehyde to methanol on the reduced surfaces, as evidenced by the presence of methoxide species at 286.3 eV in the C(1s) spectrum at 250 K following formaldehyde adsorption. Part of the formaldehyde was totally decomposed to C(a), H(a), and O(a);H(a) was involve in the reduction of formaldehyde to methanol, C(a) was oxidized to CO and CO2, while O(a) oxidized reduced titanium sites as indicated by the decrease of the XPS Ti(2p3/2) lines corresponding to Ti(x+) (x < 4). The second principal pathway for reaction of formaldehyde involved a Cannizzaro-type reaction and was only observed on fully oxidized surfaces. This reaction was responsible for the coincident formation of methoxide (286.3 eV) and formate (289.5-289.7 eV) species observed by XPS at room temperature.

KW - SINGLE-CRYSTAL SURFACES

KW - FORMIC-ACID

KW - SPECTROSCOPIC IDENTIFICATION

KW - ZINC-OXIDE

KW - PD(111) SURFACE

KW - METHANOL

KW - ADSORPTION

KW - DECOMPOSITION

KW - OXYGEN

KW - TITANIUM

M3 - Article

VL - 262

SP - 113

EP - 127

JO - Surface Science Reports

JF - Surface Science Reports

SN - 0167-5729

IS - 1-2

ER -