Precision-type cu₂o crystals unlock new possibilities for clean energy catalysts

Can crystal shapes really change how well they work with clean energy technology? New research, yes, society.

Researchers from the National Taiwan University, the National Tsing Hua University, and the National Yang Ming Ziao Tung University have found that the performance of the widely studied catalyst, the foliar oxidized insect (Cu2O), in the oxygen reduction reaction (ORR), depends heavily on which crystal plane is exposed.

This paper is published in the Journal of Materials Chemistry A.

Oxygen reduction is the central reaction of fuel cells, a device that converts chemical energy into electricity. Platinum is commonly used in this role, but is expensive and limited in supply. A more affordable alternative, Cu2O, shows surprising possibilities when used in the right form.

The team synthesized Cu2O crystals into three different shapes: Cube, Octahedra and Rhombus Dodecahedra. These shapes were blended with carbon nanotubes respectively, exposing different crystal facets {100}, {111}, and {110} respectively, respectively, and to increase conductivity.

Researchers found that the rhombus rectangular plate exposed the {110} surface provides the strongest catalytic activity in the ORR, and that the cube is most stable over time.

By combining advanced quantum simulations with lab experiments, the team discovered that oxygen molecules behave differently depending on which crystal surface they land.

The {110} surface showed the weakest grip against oxygen. This helps the reaction proceed more smoothly. This was consistent with their density functional theory (DFT) predictions and was clearly shown in the free energy diagram and 2D volcanic plots linking bond strength to catalytic performance.

However, improving performance can be costly. We found that rhombic dodecaheden crystals degrade faster during operation, possibly due to autooxidation. In contrast, cube-shaped crystals (although less reactive) were more robust over time.

This study not only helps explain why different facets perform different functions, but also helps to open the door to designing next-generation, low-cost catalysts by simply controlling the crystalline form.

“By fine-tuning the geometry of the crystal surface, they can be adjusted to their reactivity and stability, which is important for advancing sustainable energy technologies,” said Professor Jyh-Pin Chou of National Taiwan University.