Self-Assembly for Photocatalysis

Plasmonic photocatalysis is promising for increased efficiencies and tailored selectivity of catalytic processes, but typically plasmonic materials like gold or silver are catalytically not broad in scope or not very active. However, when combined with a catalytic nanomaterial, for instance, platinum or palladium, a synergistic enhancement of the photocatalytic performance can be achieved. Such bimetallic structures combine strong absorbance of visible light due to the plasmonic nanoparticles and high reactivity due to the activated catalytic material. Unfortunately, their performance in dispersion is limited due to multiple scattering and absorption events which lead to decreased light penetration into the reactor. Here, new geometries based on thin-film optical metamaterials offer an interesting new approach to maximizing light-matter interactions. In this regard, self-assembling plasmonic and catalytic NPs simultaneously into crystalline superlattices with interparticle gaps in the range of 1-6 nm leads to the formation of new polaritonic excitations with favorable properties. Firstly, high densities of so-called hotspots and nanoscale regions with strongly enhanced electromagnetic fields are formed upon interaction with light, which have been shown to significantly enhance catalytic activity. Secondly, as a result of the strong light-matter interactions in densely packed plasmonic nanoparticle supercrystals, the absorption in the material can be strongly reduced, i.e., plasmonic losses are minimized. The promising properties of bimetallic self-assembled nanoparticle supercrystals have been demonstrated recently¹, but systematic parameter studies are yet missing and many aspects of the complex interplay between the light-matter interactions and catalytic activity are not fully understood. Experimental approaches will be presented and discussed expanding the scope of the approach. Parameters under study include particle size and material, loading of the catalytic particles, structure of the supercrystals, and reaction conditions.<br/>1. Herran, M. <i>et al.</i> Plasmonic bimetallic two-dimensional supercrystals for H2 generation. <i>Nat Catal</i> <b>6</b>, 1205–1214 (2023).