Single-atom catalysts (SACs), in which
metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single-atom electrocatalysts used for the
oxygen reduction reaction (ORR),
hydrogen oxidation reaction (HOR),
hydrogen evolution reaction (HER),
formic acid oxidation reaction (FAOR), and
methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO2 reduction to methane or
methanol production while suppressing H2 evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on
TiN or
TiC nanoparticles, defective
graphene nanosheets, N-doped covalent
triazine frameworks,
graphitic carbon nitride, S-doped
zeolite-templated
carbon, and Sb-doped SnO2 surfaces. Scanning transmission electron microscopy, extended X-ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single-atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious
metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested.