Erbium-doped electrocatalyst enhances oxygen evolution reactions in acidic environments

A group of researchers has developed an electrocatalyst that promises to significantly improve the efficiency and stability of oxygen evolution reactions (OERs) in acidic environments. By incorporating a rare earth element, erbium (Er), into cobalt oxide (Co₃O₄) catalyst, the team demonstrated a new cost-effective solution that outperforms many non-precious metal catalysts, providing an alternative to more expensive noble metal-based options.

Details of the results were published in the journal ACS Catalysiswhere the study was also selected as an Editors’ Choice.

The oxygen evolution reaction, a critical process in water splitting and energy conversion, requires robust and efficient catalysts, especially under acidic conditions. Traditionally, cobalt-based catalysts have shown moderate performance due to their spinel crystal structure, which provides stability and catalytic activity. However, the introduction of Er into Co₃O₄ The catalyst marks a significant leap forward.

“Our research shows that by doping a small amount of erbium into Co₃O₄“We can improve both the activity and stability of the catalyst,” says Tianyi Wang, a JSPS postdoctoral researcher at Tohoku University’s Advanced Institute for Materials Research (WPI-AIMR) and co-author of the paper.

“Co doped with 4% erbium₃O₄ The catalyst we developed achieved an impressive overpotential of only 321 mV at 10 mA cm² and maintained its stability for more than 250 hours. This performance is comparable to, and in some cases superior to, more expensive iridium-based catalysts.

The team used advanced techniques, such as microkinetic modeling and density functional theory (DFT) calculations, to understand why this doped catalyst works so well. The incorporation of Er led to the formation of more active sites and defects in the crystal structure, which in turn increased the Co ratio³⁺ to Co²⁺ ions. This change plays a key role in generating oxygen vacancies, crucial for accelerating the OER process.

“Think of the catalyst as a road,” says Hao Li, an associate professor at WPI-AIMR and co-author of the paper. “Er doping essentially adds extra pathways, allowing more traffic to move smoothly. In this case, the traffic is the oxygen intermediates needed for the reaction. The increased number of oxygen vacancies acts as those extra pathways, speeding up the reaction.”

Furthermore, in situ Raman spectroscopy revealed that the oxygen vacancies created by Er doping were located in the octahedral sites of Co₃O₄ structure. These gaps have facilitated the development of critical intermediate species, which are essential to drive the OER process. The higher Co³⁺/Co²⁺⁺ The report further improved the catalytic activity by providing more active Co³⁺ sites to anchor these intermediaries.

“This combination of electronic and structural optimization is what really makes the catalyst special,” Wang adds. “It’s the balance between these two factors that allows us to achieve such high performance.”

This research opens new possibilities for the design of high-performance catalysts that are both cost-effective and sustainable. In the future, the researchers plan to focus more on non-precious metal doping to design high-performance, low-cost, and readily available electrocatalysts.