Dual and Triple Atom Electrocatalysts for Energy Conversion (CO₂RR, NRR, ORR, OER, and HER): Synthesis, Characterization, and Activity Evaluation

Dual and triple atom catalysts (DACs and TACs) are an emerging field of heterogeneous catalysis research. They share properties with single atom catalysts (SACs), such as maximizing dispersion of metals and the ability to circumvent the traditional scaling relations that limit extended surfaces. DACs and TACs additionally provide adjacent sites that are necessary for certain reaction mechanisms and add to the tunability of the electronic structure and binding energies. DACs and TACs are, however, inherently difficult to selectively synthesize and characterize. Characterization and activity evaluation are prone to misinterpretation, adding confusion to the already complex field. In this review, we investigate the current progress of DACs for important electrochemical reactions in energy conversion and storage. We further discuss current and future synthesis methods for DACs and TACs and focus on common pitfalls in characterization and activity evaluation.