# Fine cubic Cu2O nanocrystals as highly selective catalyst for propylene epoxidation with molecular oxygen

## TL;DR

Researchers found that cubic Cu2O nanocrystals can efficiently and selectively convert propylene and oxygen into propylene oxide at moderate temperatures.

## Contribution

The study introduces cubic Cu2O nanocrystals as a novel, highly selective catalyst for propylene epoxidation with molecular oxygen.

## Key findings

- Cu2O nanocrystals achieve over 80% propylene oxide selectivity at 90–110 °C.
- Weakly-adsorbed O2 species at {110} edges enable low-barrier reactions at low temperatures.
- High temperatures reduce selectivity due to surface lattice oxygen species and side reactions.

## Abstract

Propylene epoxidation with O2 to propylene oxide is a very valuable reaction but remains as a long-standing challenge due to unavailable efficient catalysts with high selectivity. Herein, we successfully explore 27 nm-sized cubic Cu2O nanocrystals enclosed with {100} faces and {110} edges as a highly selective catalyst for propylene epoxidation with O2, which acquires propylene oxide selectivity of more than 80% at 90–110 °C. Propylene epoxidation with weakly-adsorbed O2 species at the {110} edge sites exhibits a low barrier and is the dominant reaction occurring at low reaction temperatures, leading to the high propylene oxide selectivity. Such a weakly-adsorbed O2 species is not stable at high reaction temperatures, and the surface lattice oxygen species becomes the active oxygen species to participate in propylene epoxidation to propylene oxide and propylene partial oxidation to acrolein at the {110} edge sites and propylene combustion to CO2 at the {100} face sites, which all exhibit high barriers and result in decreased propylene oxide selectivity.

Direct propylene epoxidation with O2 to form propylene oxide (PO) selectively is a challenge. Here, the authors explore 27 nm-sized cubic Cu2O nanocrystals as thermocatalysts for this reaction which facilitate PO production with high selectivity, >80%, at moderate temperatures of 90–110 °C.