Photodeposition of metals from inks and their application in photocatalysis

Abstract

Films of Ag, Pt and Ag nanoparticles are photodeposited onto a range of commercial TiO2 based photocatalytic materials, such as paint, tile, awning fabric and glass, as well as a TiO2 sol-gel film, using an aqueous ink containing a sacrificial electron donor, glycerol, and the appropriate metal salt. The photodeposited metal films appear to be comprised of a fine covering of nanoparticular metal islands distributed evenly across the surface of the TiO2 sol-gel film, with some large aggregated particles for Pt (106 nm) and Au (33 nm). The rate of deposition of Ag is particularly fast, since a 10 s exposure to 2 mW cm-2 UVA light produces a very noticeable colour change, which is ca. 60 times that of the other two metal-ion containing inks. When combined with a photomask, the metal inks are used to create finely detailed metal film images on the surfaces of a wide variety of different, mainly commercial, photocatalytic materials; a fine metal mesh photomask is used to make metal micropatterns. When used to promote the photocatalysed oxidation of organic pollutants dissolved in aqueous solution, such as 4CP and MB, the enhancement in photocatalytic activity (compared to a plain TiO2 film) exhibited by a photodeposited Pt on TiO2 film is modest (16-35%), however, the enhancement is marked (234%) for the photocatalysed oxidation of CO to CO2. In contrast, the Au and Ag films appear to depress the inherent activity of the naked TiO2. The Pt/TiO2 film also enhances significantly the photocatalysed oxidation of a film of soot (179%) but not of stearic acid (-23%); the Ag and Au films appear to impede the former reaction. The Pt/TiO2 film exhibits the most significant enhancement in rate for the photocatalysed reduction of water to H2 by ethanol, i.e. 62 times that of the Ag/TiO2 film, which exhibits only a modest activity, which in turn is better than a naked TiO2 film which shows no activity. The potential of the metal (ion) inks to more easily make photodeposited metal films on semiconductor photocatalyst films is discussed briefly.

Modelled kinetics of the rate of hydrogen evolution as a function of metal catalyst loading in the photocatalysed reforming of methanol by Pt (or Pd)/TiO2

“…In addition, this ideal pollutant must be readily oxidised by the photogenerated holes at the surface of the surrounding, metal free TiO 2 . One possible contender for this role as solid pollutant is soot, which when deposited using a candle, tends to form a brown coloured very porous layer of carbon which is oxidisable by holes photogenerated on TiO 2 [26,27,32,33].…”

“…Despite the concerns noted above, the MSI kinetic is not without merit, since there is evidence of spill-over and extended reaction zones from other photocatalytic studies of metal-deposited photocatalytic films [11,26,27]. In particular, in a recent paper from this group on the photocatalysed oxidation of soot by a TiO 2 film with a photodeposited line, or 'wire', (ca.…”

“…In particular, in a recent paper from this group on the photocatalysed oxidation of soot by a TiO 2 film with a photodeposited line, or 'wire', (ca. 1 mm) of Pt on its surface [27] clear evidence of an extended zone of photocatalytic activity around the Pt 'wire'…”

Recent Advances in Glycerol Catalytic Valorization: A Review

“…The first cocatalysts tested were noble metals, Pt, Ru, and Au, and many research papers were published from 2017 to 2018 [238,244]. More recent publications using noble metals as cocatalysts are focused on either developing a better semiconductor [239,245,246] or developing a new synthetic method for catalyst preparation [247].…”

Ring Photocatalysis: Bands of Activation Surrounding Macro-Sized (≥1 mm Radius) Pt Islands Deposited on TiO2 Films

“…The model studies noted above , suggest that band bending can create large (up to 12–15× r o ) rings of high photocatalytic activity around Pt nanoparticles deposited on TiO 2 , but for large Pt particles, with r o , ≫ 1 μm, this electric field based effect will be negligible. , In a recent study carried out by this group, using a thin layer of soot as the pollutant, and a 1 mm wide photodeposited Pt “wire” on a TiO 2 film, it was noted that while the whole film was able to sensitize the slow photomineralisation of the soot film, via the following reaction the ca. 1 mm wide area of TiO 2 , surrounding the Pt wire, was much more active than the TiO 2 photocatalyst film laying outside this area.…”