Electrocatalytic activity and dissolution stability of high entropy alloys at the atomic scale

Project Information

HEACAT

Grant agreement ID: 101105293

DOI

10.3030/101105293

Project closed

EC signature date 17 April 2023

Start date 1 November 2023

End date 31 October 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 214 934,40

Coordinated by

AARHUS UNIVERSITET
Denmark

Periodic Reporting for period 1 - HEACAT (Electrocatalytic activity and dissolution stability of high entropy alloys at the atomic scale)

Reporting period: 2023-11-01 to 2025-10-31

Summary of the context and overall objectives of the project

The HEACAT project addresses one of the most pressing challenges in sustainable energy: developing efficient and durable catalysts for water splitting, a key process for producing green hydrogen. Current catalysts often rely on scarce noble metals while non-noble metal alternatives frequently lack stability under harsh operating conditions. High-entropy alloys (HEAs), composed of multiple non-noble metallic elements in near-equal proportions, offer a promising class of electrocatalysts thanks to their unique combination of chemical complexity, structural stability, and tunable surface properties.
The overall objective of HEACAT is to evaluate the catalytic activity and corrosion resistance of a model HEA surface for water-splitting reactions at the atomic and nanometric scales, specifically the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). To achieve this, the project developed advanced methodologies for preparing and characterizing HEA surfaces under ultra-high vacuum (UHV) conditions and for monitoring their compositional and structural evolution when exposed to oxygen, water vapor, and electrolytes. The ultimate goal is to understand how the high-entropy effect influences catalytic performance and to design strategies for optimizing activity and stability.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project successfully synthesized and characterized model HEA surfaces using state-of-the-art surface characterization techniques such as scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), including synchrotron-based XPS for high-resolution elemental analysis. We discovered that manganese (Mn) tends to evaporate at elevated temperatures, leading to surface reconstruction and compositional gradients in depth. These insights guided the development of surface engineering strategies, including controlled deposition of catalytic elements like platinum (Pt) and palladium (Pd) and morphology tuning through annealing.
We investigated oxidation mechanisms under UHV by exposing HEA surfaces to oxygen and water vapor and tracked changes in real time. The results revealed early-stage surface inhomogeneity and the formation of chromium oxide as a protective barrier, which plays a key role in corrosion resistance. Electrochemical tests in acidic and alkaline electrolytes demonstrated that HEA surfaces exhibit excellent stability and promising catalytic activity for OER. Additional studies showed that Pt additions significantly enhance OER activity without compromising durability.
Overall, the project achieved its scientific objectives and provided a comprehensive understanding of the interplay between composition, morphology, and catalytic performance in HEAs.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

HEACAT advances the state of the art by establishing a direct link between the high-entropy effect and catalytic performance for water splitting. The project demonstrated that the alloying process of a minimal addition of metal can dramatically improve OER activity while maintaining exceptional stability, as confirmed by post-electrochemical analysis showing extreme low dissolution rates. These findings open new pathways for designing cost-effective, durable catalysts for green hydrogen production.
Future work will focus on scaling up these insights to practical systems, exploring combinatorial synthesis for tailored HEA compositions, and integrating these materials into prototype electrolyzers. The results have strong potential for industrial uptake, contributing to the EU’s strategic goals for renewable energy and decarbonization.