Improved Photocatalytic Performance of TiO-Nitrogen-Doped Graphene Quantum Dot Composites Mediated by Heterogeneous Interactions.

Photocatalysis is typically monitored via analysis of phases in isolation and focuses on the removal of a target analyte from the solution phase. Here we analyze the photocatalytic action of a TiO-nitrogen-doped graphene quantum dot (NGQD) composite on a target analyte, phenol, using comprehensive multiphase NMR (CMP-NMR) which observes signals in solid, solution, and gel phases . Phenol preferentially interacts with the composite photocatalyst compared to pure TiO, increasing its effective concentration near the catalyst surface and its degradation rate. The presence of NGQDs in the composite reduced the fouling of the catalyst surface and caused a reduction of photogenerated intermediates. Increased heterogeneous interactions, likely mediated by π-π interactions, are hypothesized to cause each of these improvements in the observed photocatalytic performance by TiO-NGQDs. CMP-NMR allows the elucidation of how the photocatalytic mechanism is enhanced via material design and provides a foundation for the development of efficient photocatalysts.