Single‐Particle Kinetics Unravel Aperture‐Size Dominance in Hot‐Carrier Transfer and Product Desorption for Photocatalytic Reactions in Plasmonic Nanocavities

Why It Matters

By linking aperture size to both hot‑carrier transfer efficiency and desorption pathways, the work provides a concrete geometric lever to boost plasmonic photocatalyst performance, accelerating the development of scalable solar‑driven chemical processes.

Key Takeaways

• Medium aperture (~58 nm) yields highest turnover
• Turnover rate 0.59 s⁻¹, 2.8‑8.4× better
• Desorption shifts to substrate‑assisted mechanism
• Electric field peaks at rim, |E|max/|E|0 = 5.1
• Geometry controls adsorption, desorption, and active‑site stability

Pulse Analysis

Plasmonic nanoparticles have become a cornerstone of solar‑energy‑driven catalysis because they can harvest light and generate energetic charge carriers that drive chemical transformations. Yet, the relationship between the physical shape of a nanostructure and its catalytic output remains poorly quantified, limiting the ability to engineer reactors that consistently outperform conventional catalysts. Recent advances in single‑particle imaging have opened a window onto the microscopic events that dictate overall reaction rates, allowing researchers to isolate geometry‑dependent effects from ensemble‑averaged noise.

In the new study, a wet‑chemical route produced gold nanocups with aperture diameters spanning 35–67 nm, and each particle was interrogated under identical illumination conditions. The medium‑aperture cups (~58 nm) achieved a turnover frequency of 0.59 s⁻¹, a 2.8‑ to 8.4‑fold increase over the smallest and largest apertures. Finite‑element simulations linked this boost to a five‑fold electric‑field concentration at the rim, which amplifies hot‑carrier generation where reactants adsorb. Kinetic analysis further revealed a transition from direct product desorption to a substrate‑assisted pathway, reflected in a dominant desorption constant (k₂ ≈ 6.1 s⁻¹) and a pronounced memory effect that stabilizes active sites.

These findings translate into a practical design rule: optimizing nanocavity aperture size can simultaneously maximize light confinement and streamline mass transport, delivering higher catalytic turnover without altering material composition. For industry, this means that existing gold‑based plasmonic platforms can be retrofitted with modest geometric tweaks to achieve near‑term efficiency gains in solar‑to‑chemical processes such as CO₂ reduction or hydrogen evolution. Future work will likely explore scaling these insights to arrays and hybrid systems, paving the way for commercially viable, high‑performance photocatalytic reactors.