Precise Nanoparticle Reactant Interaction Outplays Ligand Poisoning in Visible-Light Photocatalysis

Abstract

The ability to move electrons under the influence of visible-light in an efficient manner is one of the most fundamental challenges in photocatalysis.(1−6) The “hot” charge carriers in metal nanoparticles (NPs) have been shown to participate effectively in various reductive and oxidative photocatalytic chemical transformations.(7−14) During this process, the electrons and holes, oftentimes, have to encounter the “insulating” organic ligands capped on the NPs.(15−19) Generally, the surface ligand plays a crucial role in stabilizing the NPs as well as dictating its physicochemical properties.(20−23) However, for applications in photocatalysis, where the stability as well as the surface accessibility of NPs is desirable, the role of surface ligands is conflicting. In principle, the surface ligands can “poison” a photocatalyst by hindering the (i) movement of electrons/holes (due to its insulating nature)(15,16) and (ii) accessibility of the NP surface to the reactants (due to steric effect).(17−19) The alternative is to deposit NPs onto a support or use “ligand free” NPs for catalysis.(24−27) However, the available surface area and stability of NPs are compromised during the course of catalysis.(24) Thus, metal NPs and surface ligands are two inseparable entities, and strategies have to be developed to accomplish photocatalysis by retaining and taking advantage of the ligands on the NP surface. We address this challenge by using ligands that can enhance the NP catalyst–reactant interactions, which in turn can facilitate the electron transfer process