Synergistic Enhancement of Electron and Hole Transport by Pd Single Atoms and Gradient-Distributed Ti3+ Species for High-Performance Photocatalytic Oxidation of CH4 to Oxygenates.

Abstract

Photocatalytic oxidation of methane to liquid oxygenates offers a sustainable strategy for utilizing natural gas and reducing carbon emissions. However, the efficiency of current photocatalysts remains limited by poor charge carrier utilization, particularly the ineffective migration of holes that are crucial for C─H bond activation. Herein, we report a rationally engineered TiO2 photocatalyst incorporating atomically dispersed Pd and a gradient distribution of Ti3+ species, achieving a remarkable C1 oxygenates yield of 8.14 mmol·gcat -1·h-1 with 91.3% selectivity at room temperature, surpassing most state-of-the-art photocatalysts. Comprehensive characterizations and theoretical calculations reveal that Pd single atoms accelerate electron transfer and facilitate O2 dissociation, while the gradient-distributed Ti3+ species promote hole migration from the bulk to the surface, enabling efficient CH4 activation. These spatially separated charge pathways synergistically promote the formation of •CH3 and •OOH radicals, which couple to generate CH3OOH and subsequently convert into methanol and formaldehyde.