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

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 g_NF⁻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.