Tailoring TiO2 Morphology and Surface Chemistry for Optimized Photocatalytic Activity in rGO Hybrids

TiO2–reduced graphene oxide (rGO) hybrids were investigated in this study to elucidate how TiO2 morphology and surface chemistry govern charge-transfer pathways and, ultimately, reaction selectivity. Three anatase TiO2 nanostructures were compared: bipyramids predominantly exposing {101} facets (bipy) and two nanosheet-like samples enriched in {001} facets, either fluorinated (n-sh) or thermally defluorinated and {101}-enriched (n-sh_873K). A constant rGO loading (2 wt.%) was introduced via in situ hydrazine reduction of graphene oxide in the presence of TiO2. Photocatalytic activity was evaluated under Xe-lamp irradiation in two model reactions probing oxidative and reductive pathways: phenol degradation and H2 evolution using formic acid as a scavenger. rGO systematically enhanced phenol degradation for all morphologies, with bipy+rGO showing the highest activity. In contrast, H2 evolution was consistently suppressed upon rGO incorporation across all TiO2 samples, although the bipyramidal morphology remained the most active within each series. These results highlight that facet exposure and surface functionalization dictate the beneficial or detrimental role of rGO depending on the targeted photocatalytic pathway.