A Pd-based plasmonic photocatalyst for nitrogen fixation through an antenna-reactor mechanism

Computational Discovery of Design Principles for Plasmon-Driven Bond Activation on Alloy Antenna Reactors

Plasmonic "antenna reactor" alloys, consisting of a plasmonic material doped with a catalytically active metal, show great promise for efficient photocatalysis. However, while simple, intuitive, and approximate design principles such as the Sabatier principle have been developed for thermal and electrocatalysis, similar design principles for plasmonic catalysts remain elusive. Here, we develop these simple design principles by using real-time, time-dependent density functional theory to study small molecule activation (CH4, CO2, H2O, and N2) on a number of Cu-based antenna reactors and elucidate trends. We first show that this technique gives results consistent with experimental plasmonic catalysis studies. We then identify promising, previously untested antenna reactors for these molecules. Next, we find that, for a given molecule, bond activation correlates with the size of the charge oscillations between the nanoparticle and molecule as quantified by the standard deviation over the propagation time. Furthermore, the orbital overlap between the dopant and molecule also roughly correlates with the bond activation. For CH4, N2, and H2O, a greater overlap leads to higher activation. For CO2, the trend is reversed because a greater overlap leads to higher chemical activation upon adsorption, which inhibits photoactivation. Hence, the orbital overlap can be used as a computationally efficient and intuitively simple predictor of photoactivation for the initial screening of plasmonic catalysts.

Promoting Photon-to-Chemical Conversion through a Dielectric Antenna-Hybrid Bilayered Reactor Configuration

The application of scattered light via an antenna-reactor configuration is promising for converting thermocatalysts into photocatalysts. However, the efficiency of dielectric antennas in photon-to-chemical conversion remains suboptimal. Herein, we present an effective approach to promote light utilization efficiency by designing dielectric antenna-hybrid bilayered reactors. Experimental studies and finite-difference time-domain simulations demonstrate that the engineered SiO2-carbon/metal dielectric antenna-hybrid bilayered reactors exhibit a synergy of absorption superposition and electric field confinement between carbon and metals, leading to the improved absorption of scattered light, upgraded charge carriers density, and ultimately promoted photoactivity in hydrogenating chlorobenzene with an average benzene formation rate of 18 258 μmol g-1 h-1, outperforming the reported results. Notably, the carbon interlayer proves to be more effective than the commonly explored dielectric TiO2 interlayer in boosting the benzene formation rate by over 3 times. This research paves the way for promoting near-field scattered photon-to-chemical conversion through a dielectric antenna-hybrid reactor configuration.

Photosynthetic System Based on a Polyoxometalate-Based Dehydrated Metal-Organic Framework for Nitrogen Fixation

In nature, biological nitrogen fixation is accomplished through the π-back-bonding mechanism of nitrogenase, which poses significant challenges for mimic artificial systems, thanks to the activation barrier associated with the N≡N bond. Consequently, this motivates us to develop efficient and reusable photocatalysts for artificial nitrogen fixation under mild conditions. We employ a charge-assisted self-assembly process toward encapsulating one polyoxometalate (POM) within a dehydrated Zr-based metal-organic framework (d-UiO-66) exhibiting nitrogen photofixation activities, thereby constructing an enzyme-mimicking photocatalyst. The dehydration of d-UiO-66 is favorable for facilitating nitrogen chemisorption and activation via the unpaired d-orbital electron at the [Zr6O6] cluster. The incorporation of POM guests enhanced the charge separation in the composites, thereby facilitating the transfer of photoexcited electrons into the π* antibonding orbital of chemisorbed N2 for efficient nitrogen fixation. Simultaneously, the catalytic efficiency of SiW9Fe3@d-UiO-66 is enhanced by 9.0 times compared to that of d-UiO-66. Moreover, SiW9Fe3@d-UiO-66 exhibits an apparent quantum efficiency (AQE) of 0.254% at 550 nm. The tactics of "working-in-tandem" achieved by POMs and d-UiO-66 are extremely vital for enhancing artificial ammonia synthesis. This study presents a paradigm for the development of an efficient artificial catalyst for nitrogen photofixation, aiming to mimic the process of biological nitrogen fixation.