RGO-wrapped Ag-doped TiO2 nanofibers for photocatalytic CO2 reduction under visible light

Abstract

The design of uniform graphene/noble-metal/semiconductor ternary nanocomposites without agglomeration or restacking of graphene for robust CO2 photoreduction is still challenging. This study demonstrates a strategy for fabricating reduced graphene oxide (rGO)-wrapped Ag/TiO2 nanofibers (NFs). Coaxial electrospinning with a negative electric potential resulted in core-shell NFs with aligned rGO wrapped around the entire fiber and Ag+ concentrated underneath the rGO layer. rGO-wrapped Ag/TiO2 NFs with a concentrated and uniformly distributed Ag layer on the TiO2 were then fabricated by subsequent thermal treatment. rGO monolayers and surface-concentrated Ag are beneficial for transporting and collecting photogenerated electrons for CO2 reduction as well as facilitating the light harvesting ability to extend the light response from the UV to visible region without shielding. Under visible light, rGO/Ag/TiO2 NFs with all these benefits exhibited 25-fold higher CO2 to CH4 photoreduction performance than bare TiO2 NFs, yielding 4.301 μmol gNF−1 of CH4 in 7 h. As wrapping rGO around the whole fiber increased the structural stability of the ternary nanocomposite, rGO/Ag/TiO2 NFs showed a consistent CO2 to CH4 photoreduction efficiency even after six cycles of testing for 17 h. The fabrication technique for rGO/Ag/TiO2 NFs presented in this study will contribute to the development of graphene/noble-metal/semiconductor ternary nanocomposites with high interfacial contact and charge separation for the efficient photoreduction of CO2 to CH4 under visible light.