Robust Hollow Spheres Consisting of Alternating Titania Nanosheets and Graphene Nanosheets with High Photocatalytic Activity for CO2 Conversion into Renewable Fuels

Abstract

Robust hollow spheres consisting of molecular‐scale alternating titania (Ti 0.91 O 2) nanosheets and graphene (G) nanosheets are successfully fabricated by a layer‐by‐layer assembly technique with polymer beads as sacrificial templates using a microwave irradiation technique to simultaneously remove the template and reduce graphene oxide into graphene. The molecular scale, 2D contact of Ti 0.91 O 2 nanosheets and G nanosheets in the hollow spheres is distinctly different from the prevenient G‐based TiO 2 nanocomposites prepared by simple integration of TiO 2 and G nanosheets. The nine times increase of the photocatalytic activity of G‐Ti 0.91 O 2 hollow spheres relative to commercial P25 TiO 2 is confirmed with photoreduction of CO 2 into renewable fuels (CO and CH 4). The large enhancement in the photocatalytic activity benefits from: 1) the ultrathin nature of Ti 0.91 O 2 nanosheets allowing charge carriers to move rapidly onto the surface to participate in the photoreduction reaction; 2) the sufficiently compact stacking of ultrathin Ti 0.91 O 2 nanosheets with G nanosheets allowing the photogenerated electron to transfer fast from the Ti 0.91 O 2 nanosheets to G to enhance lifetime of the charge carriers; and 3) the hollow structure potentially acting as a photon trap‐well to allow the multiscattering of incident light for the enhancement of light absorption.