UC Merced

Metallic nanocrystals have gained growing interest in photocatalysis applications due to their robust nature for multicycle operation, strong light absorption, and relatively new catalytic mechanisms. Historically, photocatalysis induced by localized surface plasmon resonance (plasmon resonance for short) of these particles has been studied widely for more than a decade, but photocatalysis originating from interband transitions is still underexplored. In order to build a comprehensive map from photon utilization to hot-carrier harvesting, and related photocatalysis, the systematic comparison between plasmon resonance and interband transition needs to be conducted in light of hot carriers-mediated reaction. The energy levels, population, dynamics, and heating effect of those hot carriers, and as followed, the charge transfer, reaction pathway, and kinetics are all necessary to be discussed. In this dissertation, the physical picture and related properties of interband transition and plasmon resonance are reviewed, then some systematic approaches to evaluate these two excitations are demonstrated. As follows, the porous Palladium nanoparticles as the model catalysts with dominant spectra features corresponding to the interband transitions were employed for mechanistic insights. We have demonstrated that under shorter wavelengths, deeper holes in the d-band can catalyze the oxidative addition of aryl halide R-X onto Pd0 at the nanoparticles’ surface to form R-PdII-X complex, thus accelerating the rate-determining step of the catalytic cycle, eventually increase the quantum yield of photocatalyzed Suzuki-Miyaura reactions. In the meantime, we have proved and quantified the effect of photocharging towards nanoparticle photocatalysis, as an underlying and often overlooked mechanism. We have built a proportional relation between accumulated charge and separate catalytic performance, which should deserve more attention in the future. Furthermore, we have been exploring the possibility of using earth-abundant metals for sustainable photocatalysis and utilizing the intrinsic interband transitions in these metals to search for new catalytic properties. Combined with the electronic and band structure of Au, Pd, and Co metals, we have rationalized the interband transitions in the metal-adsorbate hybridized states of those three metals and confirmed the contribution of both interaction strength between metal and adsorbates and energy states of hot carriers from interband transitions to photocatalysis. And the cobalt-based metallic nanoparticle photocatalysts were proved to be a good candidate for designing better energy alignment between the d-band structure and interband transition than Au and Pd nanoparticles, which leads us to shift from noble to non-noble metallic nanoparticle photocatalyst and a sustainable future. Eventually, we have provided some future perspectives towards the design for non-noble-metal-based nanoparticle photocatalysts and related mechanistic insights of the hot-carrier behavior from interband transitions.