Oxygen-Cluster-Modified Anatase with Graphene Leads to Efficient and Recyclable Photo-Catalytic Conversion of CO(2) to CH(4) Supported by the Positron Annihilation Study

Anatase TiO(2) hollow nanoboxes were synthesized and combined with the graphene oxide to get nanocomposite of TiO(2)/rGO (TG). Graphene oxide was used to modify the Oxygen-Clusters and bulk to surface defects. Anatase and TG composite were characterized with the positron annihilation, XPS, EPR, EIS and photocurrent response analysis. The relative affects of defects on the photocatalytic reduction (CO(2) to CH(4)) were studied. The TG composites showed highest photo-catalytic activity after GO coupling (49 µmol g(−1) h(−1)), 28.6 times higher photocurrent yields much higher quantum efficiency (3.17%@400 nm) when compared to the TiO(2) nanoboxes. The mechanism of enhanced photo-catalytic CO(2) conversion to CH(4) elucidated through electrochemical and photo-catalytic experiments with traceable isotope containing carbon dioxide ((13)CO(2)). For the first time we discovered that diminishing the comparative concentration ratio of anatase from the bulk to surface defects could significantly increase the conversion of CO(2) to CH(4).