Role of Functional Groups in H2 Production from Small Organic Molecules Over Noble-Metal-Free Tio2 Under Photohydrothermal Activation

Abstract

Nouha Mediouni, Frederic Dappozze, Gilles Berhault and Chantal Guillard

This study aims to investigate the transformation mechanisms of simple organic molecules containing one or two carbon atoms and functional groups such as alcohols, aldehydes, or carboxylic acids, under photohydrothermal treatment (TPUV) using TiO2 UV100 as a photocatalyst in an inert atmosphere under UV irradiation. The main objective is to better understand the processes involved in TPUV by monitoring both liquid and gaseous products formed during the reaction. A comparative approach was adopted, evaluating the behavior of each molecule under individual thermal catalysis (TP) and photocatalytic (PUV) treatments, as well as under the combined TPUV process, all in the presence of TiO2 and inert gas. The impact of temperature and pressure was studied on only one compound, glyoxylic acid in order to assess its influence on the transformation and product formation. The study markedly reveals different behaviors depending on the nature of the functional group, particularly for molecules containing aldehyde groups. Moreover, with the exception of those molecules containing an aldehyde group, the coupled TPUV process led to higher H2 production compared to individual processes. This difference is discussed in terms of reduction of aldehyde function in competition with H2 formation. These findings provide new insights into the reactivity of small organic compounds under combined photonic and hydrothermal activation of TiO2 and highlighting its potential as an efficient noble-metal-free strategy for photocatalytic applications.

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