Correlating Carrier Dynamics and Photocatalytic Hydrogen Generation in Pt Decorated CdSe Tetrapods as a Function of Cocatalyst Size

We investigate photoinduced carrier dynamics by time resolved terahertz spectroscopy (TRTS) in Pt nanoparticle decorated CdSe tetrapods as a function of Pt nanoparticles size (and identical areal density). We find that the collection efficiency of electrons photo generated in the tetrapods by the Pt particle increases as a function of Pt nanoparticle size. However, the photocatalytic H-2 generation efficiency is reduced for tetrapods decorated with larger Pt particles. Our results demonstrate a competition between electron capture efficiency at the semiconducting/metal interface, increasing with nanoparticles size, and electron release efficiency at the metal/water interface, decreasing with nanoparticles size. This trade-off defines an optimum for photocatalytic H-2 generation in Pt cocatalyst decorated CdSe tetrapods as a function of Pt size.