Electronic Structure Engineering in MXene SACs: Unveiling the Role of Mixed Termination for ORR/OER Bifunctionality

Why It Matters

Optimizing termination chemistry unlocks MXenes as versatile, low‑cost bifunctional catalysts for fuel cells and metal‑air batteries, accelerating the transition to sustainable energy technologies.

Key Takeaways

• Mixed O/Cl terminations tune MXene electronic structure
• Optimized OH* adsorption improves ORR and OER activity
• Ti2COXClY single-atom catalysts achieve bifunctional performance
• Precise termination ratio serves as activity descriptor
• Findings guide design of high-performance MXene SACs

Pulse Analysis

MXenes have emerged as a versatile platform for electrocatalysis because their two‑dimensional carbide or nitride cores can be functionalized with a variety of surface groups. This tunability is especially valuable for single‑atom catalysts (SACs), where the electronic environment of the isolated metal atom dictates activity and selectivity. Historically, research has focused on uniform terminations such as –O, –F, or –OH, but real‑world synthesis often yields mixed terminations. Understanding how these heterogeneous groups interact with the MXene lattice opens a pathway to engineer catalyst properties at the atomic level.

The recent work on Ti2COXClY demonstrates that deliberately adjusting the O‑to‑Cl ratio on a Ti2C backbone can modulate the d‑band center of the anchored metal atom, directly influencing the binding strength of the OH* intermediate that governs both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Computational screening revealed an optimal window where OH* adsorption is neither too strong nor too weak, delivering superior bifunctional performance without changing the active site. The authors propose the O/Cl termination proportion as a quantitative descriptor, bridging electronic structure theory with experimental catalyst design.

From a commercial perspective, this descriptor‑driven approach reduces trial‑and‑error synthesis, accelerating the development of cost‑effective MXene‑based electrodes for next‑generation fuel cells and metal‑air batteries. The ability to fine‑tune activity through surface chemistry also suggests compatibility with scalable production methods such as chemical vapor deposition or solution‑phase etching. Future research will likely explore other mixed‑termination combinations, integrate machine‑learning models to predict optimal ratios, and validate performance in full‑cell configurations. Ultimately, mixed‑termination engineering could become a cornerstone of sustainable electrocatalyst design.