A systematic study of photocatalytic H2 production from propionic acid solution over Pt/TiO2 photocatalyst

Abstract

SUMMARYThe propionic acid (HPr) is one of the main by-products during fermentative H 2 process. To efficiently convert HPr to H 2 gas, photocatalytic H 2 production from HPr solution with the use of Pt/TiO 2 photocatalyst under ultraviolet light has been studied in this research. The Pt/TiO 2 photocatalyst has been prepared by the sol-gel method and further characterized by X-ray diffraction, TEM and XPS. Effects of Pt loading amount, HPr concentration, initial pH value on photocatalytic H 2 production have been investigated in detail. From practical point of view, the H 2 evolution from HPr solution under UV irradiation for prolonged time has been studied as well. The Langmuir model can be able to describe the relationship between HPr concentration with the maximum rate of H 2 production. The apparent quantum efficiency and apparent energy conversion efficiency are found to 1.65 and 0.72%, respectively. To better understand the photocatalytic H 2 process over Pt/TiO 2 , a possible mechanism for the degradation of HPr has been proposed as well. Based on our results, an efficient route for hydrogen production from renewable biomass can be established by coupling biological H 2 production process with photocatalytic H 2 production process.

Characterisation of photocatalytic degradation of odorous compounds associated with livestock facilities by means of PTR-MS

“…AA was found from the degradation of PA, BA and VA, which is consistent with previous studies [50,61,62]. Besides the formation of AA from the degradation of PA, ethanol, acetaldehyde, methanol and formic acid were also the intermediates [62]. Guillard [61] has found similar intermediates from the degradation of BA, and also proposes the mechanism of the degradation, which includes the formation of alkyl radicals and the reaction of the alkyl radicals with O 2 or H 2 O.…”

“…CH 4 , CO 2 and C 2 H 6 could not be analysed by PTR-MS due to their low proton affinities, but acids, alcohols, and aldehydes could all be found in most of the photocatalytic reactions of VFAs (Table 6). AA was found from the degradation of PA, BA and VA, which is consistent with previous studies [50,61,62]. Besides the formation of AA from the degradation of PA, ethanol, acetaldehyde, methanol and formic acid were also the intermediates [62].…”

“…Carboxylic acids in the gas phase can react with OH Å radicals, which could lead to breaking of the methyl C-H, and subsequent formation of CH 4 , CO 2 and a small amount of C 2 H 6 [70]. In the aqueous phase, carboxylic acids could also photocatalytically decompose to alcohols, acids, and aldehydes (or ketones) [62]. CH 4 , CO 2 and C 2 H 6 could not be analysed by PTR-MS due to their low proton affinities, but acids, alcohols, and aldehydes could all be found in most of the photocatalytic reactions of VFAs (Table 6).…”

“…As discussed in the previous section, the removal efficiencies of AA were also the lowest in the test of concentration dependence (Table 2). It should be noted, however, that the four types of VFAs were mixed together in the study; and that AA is a potential by-product during the photocatalytic reactions of PA, BA and VA [50,61,62] and therefore that the AA produced from those processes might influence the calculation of the removal efficiency of AA.…”

“…The carboxylic acids were mainly trapped by the positively charged holes, and then degraded by OH Å radicals [50,61,62,69]. Carboxylic acids in the gas phase can react with OH Å radicals, which could lead to breaking of the methyl C-H, and subsequent formation of CH 4 , CO 2 and a small amount of C 2 H 6 [70].…”