Unlocking Clean Energy's Potential: How Topological Surfaces Enhance Catalysts
The quest for sustainable energy solutions has led to a spotlight on fuel cells and metal-air batteries, which are poised to play a pivotal role in our low-carbon future. However, a significant hurdle lies in the oxygen reduction reaction (ORR), a process that often proceeds at a snail's pace on most materials, thereby limiting efficiency and driving up costs. The challenge? Finding catalysts that can accelerate this reaction, thereby reducing our energy footprint.
Enter two-dimensional (2D) topological materials, which have emerged as promising electrocatalysts. Their unique electronic properties, stemming from spin-orbit coupling (SOC), create robust topological surface states (TSSs) that enhance charge transport. But here's where it gets intriguing: most studies have assumed these surfaces remain pristine and unchanged during reactions, a simplification that doesn't hold up in real-world scenarios.
In reality, catalyst surfaces are far from perfect. They constantly interact with the surrounding electrolyte and reaction intermediates, forming electrochemical surface states (ESSs). To truly harness the potential of 2D topological materials, scientists need to understand how these realistic surfaces impact their topological properties and catalytic performance.
To shed light on this, researchers at Tohoku University turned to monolayer platinum bismuthide (PtBi₂) as a model topological electrocatalyst. By combining quantum-level calculations with models that account for pH-dependent reactions, they uncovered the catalyst's true working surface under oxygen reduction conditions.
Their findings revealed a surprising twist: PtBi₂ is stabilized at ORR-relevant potentials with a nearly monolayer of hydroxyl (HO) species covering its surface. This means the active surface isn't the idealized topological surface but an HO-induced electrochemical surface state formed during operation. But here's the fascinating part: this surface reconstruction doesn't negate the material's topological nature.
Instead, it reshapes the electronic landscape, creating localized SOC-enabled surface states and a flat-band-like feature with a high density of electronic states near the Fermi level. These features enhance electronic coupling to ORR intermediates and reduce sensitivity to interfacial dipoles, much like roads guiding crowded traffic.
By explicitly considering pH effects, the researchers further predicted that PtBi₂ achieves near-peak ORR activity in alkaline environments. This underscores the importance of evaluating catalytic performance under realistic electrochemical conditions rather than relying on idealized surface models.
"Our findings demonstrate that topological surface states can not only survive but also be optimized by electrochemical reconstruction," says Hao Li, a Distinguished Professor at Tohoku University's WPI-AIMR. "This provides a practical design principle for next-generation electrocatalysts, where quantum topology and electrochemical surface chemistry must be considered in harmony."
The computational results have been made publicly available on the Digital Catalysis Platform (https://www.digcat.org/), the world's first and largest experimental + computational catalysis database, developed by the Hao Li Lab.
The research was published in the Journal of Physical Chemistry Letters on December 9, 2025, under the title "2D Topological Electrocatalysts with Spin−Orbit Coupling: Interplay between the 'Electrochemical' and 'Topological' Surface States."
Authors: Heng Liu, Tran Ba Hung, Yuan Wang, Di Zhang, Yiming Lu, and Hao Li
DOI: 10.1021/acs.jpclett.5c03589 (https://doi.org/10.1021/acs.jpclett.5c03589)
