Highly Efficient and Stable CO2 Reduction Photocatalyst with a Hierarchical Structure of Mesoporous TiO2 on 3D Graphene with Few-Layered MoS2
2018
Jung, Hyunju | Cho, Kyeong Min | Kim, Kyoung Hwan | Yoo, Hae-Wook | Al-Saggaf, Ahmed | Gereige, Issam | Jung, Hee-Tae
The development of photocatalysts of CO₂ reduction based on stable and Earth-abundant materials is essential for utilizing solar energy and storing it in chemical forms. Here, we report the synthesis and characterization of a composite material consisting of a few layers of MoS₂ on a hierarchical porous structure of mesoporous TiO₂ and macroporous 3D graphene aerogel (TGM) as a high-performance, robust, noble-metal-free photocatalyst of CO₂ reduction. The hierarchical structure contributed to the high photocatalytic catalyst performance, which was investigated by controlling the morphologies of the mesopores and macropores. By optimizing the relative amounts of each component and the configuration of the composite, a TGM system was fabricated. The resulting TGM showed a lower extent of charge recombination and a higher photocurrent density, and hence a higher CO photoconversion rate (92.33 μmol CO/g·h) than those of other composite combinations, i.e., bare TiO₂, TiO₂-graphene, TiO₂-MoS₂, and TiO₂-graphene multiple-layered MoS₂. Also, the role of each component and the underlying mechanism in the catalysis of the reaction by TGM were investigated. The long-term stability of the TGM composite was tested and compared with that of a TiO₂-graphene-Ag composite. Over the course of 15 cycles, the TGM composite retained its original conversion rate, while the activity of the TiO₂-graphene-Ag composite decreased. The hierarchical porous structure with mesoporous TiO₂ and a few layers of MoS₂ on macroporous 3D graphene is expected to have great potential as an affordable, robust, high-efficiency CO-selective photocatalyst of CO₂ reduction.
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