Photochemistry of NO Chemisorbed on TiO₂(110) and TiO₂ Powders

Abstract

The photodecomposition of chemisorbed NO has been studied using ultraviolet radiation of (3.96 ( 0.07) eV. Both the TiO 2 (110) single-crystal substrate and high area compressed TiO 2 powders have been investigated. A primary photoproduct is N 2 O gas, which desorbs immediately upon irradiation of the TiO 2 (110) surface. Following this process, the photoproduction of NO gas is observed to reach a maximum rate and then to decline. The cross section for the initial photodepletion of NO is about 1 × 10 -15 cm 2 , corresponding to a quantum efficiency near unity. In contrast, the quantum efficiencies of gas-phase N 2 O and NO photoproduction from chemisorbed NO on TiO 2 are only in the range 10 -2 -10 -4 , indicating that NO photodecomposition primarily yields an intermediate photoproduct (N 2 O) which is captured on the crystal surface at 118 K. Studies of the infrared spectral behavior of NO on powdered and compressed high area TiO 2 powders during photolysis confirm that much of the N 2 O photoproduct is retained on the surface. Furthermore, the infrared studies indicate that the penetration of ultraviolet light into the powder occurs to a depth of order 0.003 cm, which is very large compared to the light attenuation length known for individual TiO 2 crystals (200 Å). This effect is thought to be due to light transport effects at the particle boundaries in the compressed powder, and this effect therefore is favorable for photoprocesses using powders. Evidence for sub-bandgap excitation of chemisorbed NO, leading to N 2 O production is presented.

A surface science perspective on TiO2 photocatalysis

“…Photoreduction studies of nitrogencontaining molecules on TiO 2 have been diverse, including those involving NO [557,788,[881][882][883][1162][1163][1164][1165], N 2 O [705,1166], NO 2 [1167], nitrate or nitrite [1168][1169][1170], and a variety of nitro-substituted aromatics [685,[1171][1172][1173][1174][1175]. As mentioned in Section 5.2, studies on NO have been approached mainly from the perspective of using ammonia or CO to perform selective catalytic reduction [557,788,[881][882][883].…”

Synthesis, characterization, and visible light activity of new nanoparticle photocatalysts based on silver, carbon, and sulfur-doped TiO2

“…Indeed, photocatalysis emerged as a new scientific area when Fujishima and Honda carried out photolysis of water into environmentally clean fuels (hydrogen and oxygen) using a titanium dioxide electrode in an electrochemical cell [1]. Ever since, heterogeneous photocatalysis by means of TiO 2 has been widely accepted and exploited as an efficient technology for killing bacteria and degrading organic and inorganic pollutants [2][3][4][5][6][7][8][9][10][11][12][13]. Moreover, titanium dioxide (TiO 2 ) has been regarded as an excellent semiconductor photocatalyst because of its performance, low cost, nontoxicity, stability, and availability.…”

Room-temperature-adsorption behavior of acetic anhydride on a TiO2(110) surface

“…A rutile TiO 2 (1 1 0) surface is the most intensively investigated single crystal oxide surface because of the interesting behavior of TiO 2 and its use in various applications including as catalyst [1], catalyst supports [2], chemical sensors [3,4], photocatalysts [5], bio-compatible materials [6][7][8][9], pigments [10]. Consequently, detailed physical and chemical properties of TiO 2 (1 1 0) surfaces have been unveiled and are available [11].…”