The oxygen evolution
reaction (OER) is an essential anode reaction for the generation of
solar and electric fuels through water splitting or CO2
electroreduction. Mixed metal oxides containing Co, Fe, or Ni prove to
be the most promising OER electrocatalysts in alkaline medium. However,
the active sites and reaction mechanisms of these catalysts are
difficult to study due to their heterogeneous nature. Here we describe a
general synthesis of Co, Fe, and Ni-containing double-atom catalysts
from their single-atom precursors via in-situ electrochemical
transformation. Atomic-resolution microscopy and operando X-ray
absorption spectroscopy (XAS) reveal molecule-like bimetallic active
sites for these supported catalysts. Based on electrokinetic and XAS
data, we propose a complete catalytic cycle for each catalyst. These
mechanisms follow a similar O-O bond forming step and all exhibit
bimetallic cooperation. However, the mechanisms diverge in the site and
source of OH- for O-O bond formation as well as the order of proton and
electron transfer. Our work demonstrates double-atom catalysts as an
attractive platform for fundamental studies of heterogeneous OER
electrocatalysts.
Atomically dispersed Fe3+ sites catalyze efficient CO2 electroreduction to CO
