Dependence of the photocatalytic reduction of bicarbonate to formic acid by Au–TiO₂ on Au morphology and its plasmonic vibrational mode

The effect of Au morphology and its plasmonic vibration mode on the photoactivity of Au–TiO₂ nanostructures was evaluated. Here, Au nanoparticles with three distinct morphologies, i.e., nanooctahedra, nanocube, and nanorod, were successfully prepared and integrated into TiO₂ nanoparticles. The nanocatalysts were used for photocatalytic conversion of bicarbonate to formic acid for solar fuel generation. Based on the result, it is found that the integration of Au and TiO₂ resulted in a synergistic effect on the production of formic acid due to the presence of Au's SPR phenomenon. Results also demonstrated that the shape of Au nanoparticles plays a pivotal role in the improvement of Au–TiO₂ activity. From the photocatalytic experiment, Au NR-TiO₂ was found to be the most active nanocatalyst with a formic acid yield of 5.14 mmol/g cat. By using spectroscopy techniques and near-field enhancement simulation, it is believed that the photocatalytic enhancement was due to non-radiative (hot electron transfer and storage) and radiative (near-field enhancement and far-field scattering) effects. However, the additional shape-dependent variation on activity was most likely due to the radiative effects instead of non-radiative ones.