Why co-catalyst-loaded rutile facilitates photocatalytic hydrogen evolution

Abstract

The photocatalytic H2 evolution on co-catalyst loaded titania is interpreted by a new mechanism, in which the co-catalyst acts as a recombination center for hydrogen and not as a reduction site of a photoreaction.

Reactions in the Photocatalytic Conversion of Tertiary Alcohols on Rutile TiO2(110)

“…The deposition of small amounts of Pt clusters significantly increases the overall reaction rate, with higher loadings leading only to a small increase in the turnover frequency (TOF) (Figure a). This trend is in good agreement with findings from methanol photoreforming in UHV and with colloidal systems …”

“…The overall TOFs exhibit typical 1 st order behavior when the reaction is limited by reactant adsorption and 0 th order in the case of limitation by product desorption (see Figures S5 and S6). Similarly, the illumination‐dependent TOFs (see Figure S7) suggest a first‐order behavior at lower irradiation illumination intensities, which transfer into a saturation regime (zeroth order) at higher photon fluxes, as in the photoreforming of other alcohols . However, and more importantly, for platinum‐decorated TiO 2 (110) an additional side reaction becomes evident at higher pressures.…”

“…This is best illustrated for 2‐methyl‐2‐pentanol photoreforming (Scheme 2), for which all reaction products can clearly be quantified and their analysis is not affected by isobaric interference. As deposited platinum clusters enable the efficient thermal recombination of hydrogen atoms, [17a] the surface coverage of alkyl increases in the steady state with increasing pressure. Consequently, the recombination product of two radicals (i.e., hexane) accompanied by H 2 formation is detected at 5×10 −6 mbar of alcohol pressure (Figure 3 a).…”

Influence of Local Defects on the Dynamics of O–H Bond Breaking and Formation on a Magnetite Surface

“…In a recent temperature programmed desorption (TPD) experiment, Walenta and coworkers showed that even sparsely distributed Pt co-catalysts on a TiO2(110) surface can facilitate the recombinative desorption of H2 in the photocatalytic methanol reforming, thus recovering the catalytically active site and closing the catalytic cycle. 11 On some iron oxide surfaces, similar long-range diffusion of hydrogen was observed. On a thin FeO(111) film on Pt(111), for example, hydrogen diffusion occurs readily even at cryogenic temperatures.…”

Nanofibrous TiO2produced using alternating field electrospinning of titanium alkoxide precursors: crystallization and phase development

“…TiO 2 nanomaterials are increasingly used in photocatalysis, environmental remediation, sensor technology, photovoltaic structures, fuel cells, batteries, paints, plastic additives, self-cleaning surfaces, UV blockers in cosmetics, and many other applications. [1][2][3][4][5][6] The anatase polymorph of TiO 2 is the most commonly used crystalline form in such catalytic applications, [7][8][9][10] but the more thermodynamically stable rutile polymorph [11][12][13] and mixedphase 14,15 nano-titania also have their niche applications.…”