Mechanistic Study of Glucose Photoreforming over TiO2-Based Catalysts for H2 Production

Lan Lan; Helen Daly; Rehana Sung; Floriana Tuna; Nathan Skillen; Peter K J Robertson; Christopher Hardacre; Xiaolei Fan

doi:10.1021/acscatal.3c00858

Mechanistic Study of Glucose Photoreforming over TiO₂-Based Catalysts for H₂ Production

ACS Catal. 2023 Jun 13;13(13):8574-8587. doi: 10.1021/acscatal.3c00858. eCollection 2023 Jul 7.

Authors

Lan Lan¹, Helen Daly¹, Rehana Sung², Floriana Tuna^{3

4}, Nathan Skillen⁵, Peter K J Robertson⁵, Christopher Hardacre¹, Xiaolei Fan¹

Affiliations

¹ Department of Chemical Engineering, School of Engineering, The University of Manchester, Manchester M13 9PL, United Kingdom.
² Manchester Institute of Biotechnology, The University of Manchester, Manchester M13 9PL, United Kingdom.
³ Department of Chemistry, University of Manchester, Manchester, M13 9PL, United Kingdom.
⁴ Photon Science Institute, University of Manchester, Manchester, M13 9PL, United Kingdom.
⁵ School of Chemistry and Chemical Engineering, Queen's University Belfast, Belfast BT9 5AG, United Kingdom.

Abstract

Glucose is a key intermediate in cellulose photoreforming for H₂ production. This work presents a mechanistic investigation of glucose photoreforming over TiO₂ and Pt/m-TiO₂ catalysts. Analysis of the intermediates formed in the process confirmed the α-scission mechanism of glucose oxidation forming arabinose (C_n-1 sugar) and formic acid in the initial oxidation step. The selectivity to sugar products and formic acid differed over Pt/TiO₂ and TiO₂, with Pt/TiO₂ showing the lower selectivity to formic acid due to enhanced adsorption/conversion of formic acid over Pt/TiO₂. In situ ATR-IR spectroscopy of glucose photoreforming showed the presence of molecular formic acid and formate on the surface of both catalysts at low glucose conversions, suggesting that formic acid oxidation could dominate surface reactions in glucose photoreforming. Further in situ ATR-IR of formic acid photoreforming showed Pt-TiO₂ interfacial sites to be key for formic acid oxidation as TiO₂ was unable to convert adsorbed formic acid/formate. Isotopic studies of the photoreforming of formic acid in D₂O (with different concentrations) showed that the source of the protons (to form H₂ at Pt sites) was determined by the relative surface coverage of adsorbed water and formic acid.