(233d) Enhancement of Photocatalytic Reduction Reaction on TiO2 Under Solar Light Using Alternative Plasmonic Titanium Nitride Nanoparticles

In this work, we report plasmon enhanced photocatalytic reduction reaction on TiO₂ under solar light using alternative plasmonic titanium nitride nanoparticles. The excellent chemical stability at elevated temperatures and higher integrated absorption efficiency under the solar light in comparison to conventional plasmonic nanomaterials (silver and gold) make titanium nitride a promising candidate for the application. We observed an efficient production of formic acid through simultaneous photoreduction of bicarbonate and oxidation of glycerol in the presence of TiO₂/TiN composite nanocatalysts in an isothermal condition. The photocatalytic productivity of formate was 465 mM /g cat-hr using TiO₂/TiN composite, which is significantly (15 times) higher than TiO₂ alone. Most importantly, the productivity of formic acid using TiN/TiO₂ nanoparticle catalysts was found to be higher than that of similar Au/TiO₂ and Ag/TiO₂ composites. The enhancement is predicted to be due to the plasmon-induced excited charge transfer from TiN to the conduction band of TiO₂. We also found that TiN can efficiently convert excited plasmons into heat. In an adiabatic condition under solar illumination, the temperature of reactant solution can increase as much as up to 20°C from room temperature. Interestingly, at that elevated temperature, the enhancement effect of TiN is negligible. Presently comprehensive theoretical analyses in concert with transient absorption spectroscopy are in progress to unravel the exact mechanism behind our observation.