Synergistic interplay of CuOx and Pd nanodots on TiO2 for efficient and highly selective photocatalytic oxidation of CH4 to oxygenates with O2

A bimetallic CuOx and Pd decorated TiO2 photocatalyst was developed for direct oxidation of CH4 to C1 oxygenates with O2. The interplay between CuOx and Pd improved the carrier separation, facilitated O2 reduction and mediated CH4 oxidation process to inhibit overoxidation of oxygenates to CO2, which ultimately resulted in substantially increased photocatalytic performance. [Display omitted] •CuOx and Pd decorated TiO2 was prepared for photocatalytic CH4 oxidation.•CuOx promotes interfacial electrons transfer and avoids overoxidation of oxygenates.•Pd boosts the production of CH3OOH and CH3OH by lowering the reaction energy.•The synergy of CuOx and Pd remarkably enhances oxygenates’ activity and selectivity. Direct photocatalytic methane oxidation to produce liquid oxygenates offers a promising approach for the upgrading of abundant methane under mild conditions, yet it remains a formidable challenge in achieving high reaction rates while maintaining high selectivity. Herein, we report the highly dispersed CuOx and Pd nanodots decorated TiO2 for photocatalytic oxidation of CH4 with O2 at room temperature, which exhibits a remarkable C1 oxygenates production rate of 39.5 mmol·g−1·h−1 with a nearly 100 % selectivity, outperforming most of the state-of-the-art photocatalysts. Both experimental and theoretical studies suggest that the impressive photocatalytic performance is attributed to the synergy of Cu+ species and Pd nanodots. Cu+ species not only promote the interfacial electrons transfer from TiO2 to Pd, but also mediate CH4 oxidation reaction to avoid overoxidation of oxygenates to CO2, while the resulting electron-rich Pd sites boost the production of primary products (CH3OOH and CH3OH) by lowering the reaction energy. This work provides a new pathway for developing highly efficient photocatalysts for the selective conversion of methane to value-added chemicals by designing bimetallic cocatalysts.