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.