Single Atoms in Photocatalysis: Low Loading Is Good Enough!

Abstract

We disperse Pt single atoms (SAs) with different loading densities on anatase TiO 2 thin films and evaluate the photocatalytic H 2 generation as a function of the incident light intensity. We show that under common illumination intensities (such as terrestrial solar illumination), a minuscule Pt SA loading of ∼10 5 atoms μm −2 (surface Pt content ∼0.1 at.%) is sufficient to achieve a maximized H 2 production rate. This results in a maximum turnover frequency at a single Pt atom site of ∼300 H 2 molecules s −1 . For a vast majority of illumination conditions and a suitable surface configuration, it is not the density of co-catalytic sites that is rate-determining (a high loading is not needed!), but the charge carrier generation (and flux of photoelectrons to the co-catalytic centers) determines the overall reaction rate. This is in stark contrast to SA catalysis of classic chemical reactions where generally a maximum loading of reactive SA delivers a maximum activity.

Pt single atoms dispersed in a hybrid MOFox-in-nanotube structure for efficient and long-term stable photocatalytic H2 generation

“…Also, if we compare the results of this work with literature on various TiO 2 nanostructures decorated with SA co-catalysts (such as nanosheets, 19,29,37 nanotubes, 25,27,56 nanoflakes, 26 compact layers 57 ), the Pt@MOFox-in-tube structure shows excellent performance (Fig. S21†) that now is combined with a long-term stable photocatalytic H 2 evolution performance.…”

“…24,25,29,37 Nevertheless, as reported previously, extended illumination on most TiO 2 structures leads to "light-induced" single atom agglomeration. 19,27,57 According to our previous work, 19 the lightinduced destabilization of the surface-anchored Pt SAs can occur due to their interaction with the adsorbed H atoms. As a result, the bonding between Pt SAs and the TiO 2 surface can be sufficiently weakened to allow some Pt SAs to migrate on the surface and aggregate into metallic Pt nanoparticles.…”

Reactive Deposition Versus Strong Electrostatic Adsorption (SEA): A Key to Highly Active Single Atom Co‐Catalysts in Photocatalytic H2 Generation

“…Please also note that hydrolysis of the precursor H 2 PtCl 6 is the key to the formation of the active coupling agent. I.e., in the most active state of a 0.005 mM H 2 PtCl 6 [84] solution Pt(Cl) x (OH) y (H 2 O) z species are present [85][86][87][88][89] -with increasing dilution, OH − and water ligands become dominant [85] -this is key to the loss of Cl species in the reaction. If we suppress Cl − and OH − ligand exchange, by adding NaCl or HCl to the precursor, surface uptake of Pt and SA-reactivity are strongly suppressed (see Figure S12, Supporting Information).…”

Mapping Atomic-Scale Metal–Molecule Interactions: Salient Feature Extraction through Autoencoding of Vibrational Spectroscopy Data

“…The pervasiveness of catalytic processes, a drive for materials efficiency, and the minimization of precious resource utilization have developed a need for resolving molecular interactions at heterogeneous interfaces at an atomic level. , However, few methods offer this level of resolution, and none currently allow for in-operando studies. Promising techniques are emerging with submolecular sensitivity but heavily rely on indirect interpretation of spectroscopic data, making such processes prohibitively time-consuming to model. − To this end, bespoke and robust analysis methods are required that can digest large data sets to build up a comprehensive understanding of the atomic scale processes involved.…”

“…We focus on spectral changes brought about by atomic-scale features (e.g., step edges and adatoms) forming in metal surfaces during irradiation with light. These undercoordinated metal sites provide binding sites for important and often desirable metal–molecule interactions, facilitating applications such as heterogeneous catalysis, ,,, molecular electronics, memristive switching, and ultrasensitive sensing. , Despite this, a detailed understanding is still lacking as the small length scales involved and the transient nature of the atomic-scale interactions prevent systematic experimental characterization.…”