Plasmon resonant enhancement of photocatalytic solar fuel production

We have recently demonstrated plasmonic enhancement of several photochemical processes (water splitting, CH₄ formation from CO ₂, methyl orange decomposition, and CO oxidation) by integrating strongly plasmonic metal nanostructures with strongly catalytic metal oxide semiconductors. Irradiating these catalysts with visible light near the plasmon resonance frequency generates intense electric fields and immense plasmonic charge, which drive these photocatalytic processes at an accelerated rate. Enhancement factors up to 66X have been observed under visible light illumination, while, under ultraviolet radiation, we observe a 4-fold reduction in the photocatalytic activity. Finite-difference time-domain (FDTD) simulations indicate that the enhanced photocatalytic activity in the visible range is due to the local electric field enhancement near the TiO₂ surface, rather than the direct transfer of charge between the two materials. These simulation results also indicate that enhancement factors many times larger than this can be achieved if the geometry of the plasmonic nanoparticles can be optimized.