Photocatalytic H2 Production Using Pt-TiO2 in the Presence of Oxalic Acid: Influence of the Noble Metal Size and the Carrier Gas Flow Rate

Abstract

The primary objective of the experiments was to investigate the differences in the photocatalytic performance when commercially available Aeroxide P25 TiO2 photocatalyst was deposited with differently sized Pt nanoparticles with identical platinum content (1 wt%). The noble metal deposition onto the TiO2 surface was achieved by in situ chemical reduction (CRIS) or by mixing chemically reduced Pt nanoparticle containing sols to the aqueous suspensions of the photocatalysts (sol-impregnated samples, CRSIM). Fine and low-scale control of the size of resulting Pt nanoparticles was obtained through variation of the trisodium citrate concentration during the syntheses. The reducing reagent was NaBH4. Photocatalytic activity of the samples and the reaction mechanism were examined during UV irradiation (λmax = 365 nm) in the presence of oxalic acid (50 mM) as a sacrificial hole scavenger component. The H2 evolution rates proved to be strongly dependent on the Pt particle size, as well as the irradiation time. A significant change of H2 formation rate during the oxalic acid transformation was observed which is unusual. It is probably regulated both by the decomposition rate of accumulated oxalic acid and the H+/H2 redox potential on the surface of the catalyst. The later potential is influenced by the concentration of the dissolved H2 gas in the reaction mixture.

Enhanced photocatalytic H2 generation on noble metal modified TiO2 catalysts excited with visible light irradiation

“…1a). According to our previous measurements, this significant decrease also can be observed in H 2 production rates when the Pt-TiO 2 catalyst is irradiated with UV light [30]. It was confirmed by TEM measurements that the average particle diameter and size distribution of platinum does not change considerably during irradiation.…”

Research Into Greener Transportation

“…Use of sacrificial electron donors such as oxalic acid, methanol, formic acid, formaldehyde etc. were also shown to improve photocatalytic hydrogen generation efficiency of TiO 2 since these substances are easier to oxidize than water [15][16][17]. Addition of carbonate salts to water has resulted in improved hydrogen generation due to the suppression of the back reaction [18].…”

“…Water splitting by these composite catalysts have also been thoroughly investigated. The nanostructure and the crystallographic phase of TiO 2 have been found to influence crucially on the efficiency of H 2 photogeneration [15,16]. However, the efficiencies so far achieved are below 1 mmol of H 2 gas per hour for continuous illumination of solar radiation.…”

Photoelectrochemistry by Design: Tailoring the Nanoscale Structure of Pt/NiO Composites Leads to Enhanced Photoelectrochemical Hydrogen Evolution Performance

“… 35 In photocatalytic hydrogen evolution (using oxalic acid as sacrificial e – donor) over TiO 2 supported Pt nanoparticles, 3 nm sized particles showed the best activity compared to both smaller and bigger particles. 36 Photodriven CO 2 reduction was performed on Pt/TiO 2 composites, containing photodeposited ultrasmall Pt nanoparticles (below 2 nm). 37 The particle size and density on the PEC performance was also studied for Pt/Si samples, involving relatively large Pt particles (40–300 nm) on flat Si electrodes.…”