First-Row Transition Metal Antimonates for the Oxygen Reduction Reaction

The
development of inexpensive and abundant catalysts with high
activity, selectivity, and stability for the oxygen reduction reaction
(ORR) is imperative for the widespread implementation of fuel cell
devices. Herein, we present a combined theoretical–experimental
approach to discover and design first-row transition metal antimonates
as excellent electrocatalytic materials for the ORR. Theoretically,
we identify first-row transition metal antimonatesMSb2O6, where M = Mn, Fe, Co, and Nias nonprecious
metal catalysts with good oxygen binding energetics, conductivity,
thermodynamic phase stability, and aqueous stability. Among the considered
antimonates, MnSb2O6 shows the highest theoretical
ORR activity based on the 4e– ORR kinetic volcano.
Experimentally, nanoparticulate transition metal antimonate catalysts
are found to have a minimum of a 2.5-fold enhancement in intrinsic
mass activity (on transition metal mass basis) relative to the corresponding
transition metal oxide at 0.7 V vs RHE in 0.1 M KOH. MnSb2O6 is the most active catalyst under these conditions,
with a 3.5-fold enhancement on a per Mn mass activity basis and 25-fold
enhancement on a surface area basis over its antimony-free counterpart.
Electrocatalytic and material stability are demonstrated over a 5
h chronopotentiometry experiment in the stability window identified
by theoretical Pourbaix analysis. This study further highlights the
stable and electrically conductive antimonate structure as a framework
to tune the activity and selectivity of nonprecious metal oxide active
sites for ORR catalysis.