Triple-atom catalysts: Atomic-level engineering for next-generation catalytic energy conversion

In the new era of atomic catalysis, precisely manipulating atomic structures to design multiple catalytic active sites has become a central focus. Compared to single-atom catalysts and dual-atom catalysts, triple-atom catalysts (TACs) have garnered widespread attention due to their superior activity and selectivity across multiple reactive sites. Therefore, there is an urgent need to systematically review the advanced progress of the TACs. In this review, we first provide a comprehensive discussion on the definition, synthesis strategies, synergistic catalytic centers, complex electronic regulation effects, and geometrical configurations of TACs. Next, we highlight the applications of TACs in various catalytic reactions such as dual-functional oxygen reduction reaction and oxygen evolution reaction, CO₂ reduction reaction, as well as hydrogen evolution reaction and the hydrogen oxidation reaction while analyzing the complex mechanisms behind these applications to offer new insights for their rational design. Finally, we present an outlook on the potential of TACs to drive major breakthroughs in a wide range of catalytic applications, providing forward-looking guidance for the development of multi-atom catalysis.