# Single-Atom Catalysts through Pressure-Controlled Metal Diffusion

## TL;DR

This paper introduces a new method to create high-density single-atom catalysts by controlling pressure during fabrication, improving their performance and stability.

## Contribution

A novel pressure-controlled metal diffusion method enables ultra-high-density single-atom catalysts with minimized aggregation.

## Key findings

- Reducing pressure during fabrication increases single-atom loadings by nearly three times compared to ambient pressure.
- Metal hopping mechanism, revealed through simulations, enhances metal atom distribution via increased metal–ligand binding.
- Electrocatalytic tests confirm the effectiveness of the approach in achieving high active site density.

## Abstract

Single-atom catalysts
(SACs) open up new possibilities for advanced
technologies. However, a major complication in preparing high-density
single-atom sites is the aggregation of single atoms into clusters.
This complication stems from the delicate balance between the diffusion
and stabilization of metal atoms during pyrolysis. Here, we present
pressure-controlled metal diffusion as a new concept for fabricating
ultra-high-density SACs. Reducing the pressure inhibits aggregation
substantially, resulting in almost three times higher single-atom
loadings than those obtained at ambient pressure. Molecular dynamics
and computational fluid dynamics simulations reveal the role of a
metal hopping mechanism, maximizing the metal atom distribution through
an increased probability of metal–ligand binding. The investigation
of the active site density by electrocatalytic oxygen reduction validates
the robustness of our approach. The first realization of Ullmann-type
carbon–oxygen couplings catalyzed on single Cu sites demonstrates
further options for efficient heterogeneous catalysis.