Methane production via photocatalytic degradation of glucose on PtOx and PdOx-loaded TiO2

Sustainable production of CH 4 , an industrially important gas, from renewable resources presents a critical solution to energy security challenges. This study demonstrates photocatalytic conversion of glucose, a model biomass compound, to CH 4 using a metal co-catalyst loaded TiO 2 photocatalyst under ambient conditions. We confirmed that CH 4 was formed through photocatalytic reduction of CO 2 , which was generated in situ during glucose oxidation, establishing a closed-loop conversion of biomass-derived carbon within a single reaction system. PtO x -TiO 2 (x = 0, 1) exhibited significantly higher activity for CH 4 production than PdO x -TiO 2 (x = 0, 1). The CH 4 yield with PtO x loading was approximately ten times greater than that obtained with PdO x loading, with an optimal PtO x loading of 2.0 wt% yielding the highest CH 4 amount of 10.600 µmol L − 1 after 6 h. In contrast, PdO x -TiO 2 showed a higher selectivity for H 2 generation. Analysis of the reaction products, including sugars (arabinose, erythrose, and glyceraldehyde) and organic acids (formic acid, acetic acid, and gluconic acid), elucidated the glucose degradation pathways. The mechanism of CH 4 formation was identified as the methanation of CO 2 and H + , both produced during photocatalytic oxidation of glucose and water. Deuterium-labeling experiments further revealed that the hydrogen atoms in CH 4 originated from both glucose decomposition and water splitting. These findings demonstrate a novel and sustainable tandem photocatalytic process that integrates oxidation and reduction reactions on a single catalyst surface, providing mechanistic and practical insights into the direct conversion of biomass into CH 4 under mild conditions.