In-situ FT-IR study of alcohols degradation in the gas phase using different TiO2 composites

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Herein, we present an in-situ FT-IR study analysing the interactions and photocatalytic degradation of 1-butanol and methanol in the gas phase through the catalysts Hombikat-b (commercial) and EST-1023 (synthesised in lab), as well as composites of them in a range of pH between 5 and 9. Composite Homb@EST at neutral pH (Homb@EST-pH7) has presented a photocatalytic efficiency much higher than that of the separate catalysts in both the degradation of alcohols and carboxylates. Characterisation analyses have shown that EST-1023 exhibits low surface area and surface hydroxylation, which suggests practically no adsorption of alcohols at the initial stages of the process. Notwithstanding, we have determined a large concentration of surface electronic traps in EST-1023. On the contrary, Hombikat-b presents high surface area and surface hydroxylation, leading to high adsorption rates of the studied alcohols. Aggregate distribution, SEM, and HR-TEM studies have shown that neutral pH is the most appropriate condition to aggregate both catalysts, generating the so-called composite Homb@EST-pH7. The high photocatalytic capability of this composite is attributed to the transfer of photogenerated electrons from the Hombikat-b nanoparticles to the electron traps present in EST-1023, which implies a decrease in the recombination speed of the photogenerated electron-hole (e–/h+) pairs.