Improved Photocatalytic Performance of TiO₂-Nitrogen-Doped Graphene Quantum Dot Composites Mediated by Heterogeneous...

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 TiO₂-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 in situ. Phenol preferentially interacts with the composite photocatalyst compared to pure TiO₂, 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 TiO₂-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.