1 research outputs found
Identifying Key Structural Features of IrO<sub>x</sub> Water Splitting Catalysts
Hydrogen production by electrocatalytic
water splitting will play a key role in the realization of a sustainable
energy supply. Owing to their relatively high stability and activity,
iridium (hydr)oxides have been identified as the most promising catalysts
for the oxidation of water. Comprehensive spectroscopic and theoretical
studies on the basis of rutile IrO<sub>2</sub> have provided insight
about the electronic structure of the active X-ray amorphous phase.
However, due to the absence of long-range order and missing information
about the local arrangement of structural units, our present understanding
of the active phase is very unsatisfying. In this work, using a combination
of real-space atomic scale imaging with atomic pair distribution function
analysis and local measurements of the electronic structure, we identify
key structural motifs that are associated with high water splitting
activity. Comparison of two X-ray amorphous phases with distinctively
different electrocatalytic performance reveals that high activity
is linked to the ratio between corner- and edge-sharing IrO<sub>6</sub> octahedra. We show that the active and stable phase consists of
single unit cell sized hollandite-like structural domains that are
cross-linked through undercoordinated oxygen/iridium atoms. In the
less active phase, the presence of the rutile phase structural motif
results in a faster structural collapse and deactivation. The presented
results provide insight into the structure–activity relationship
and promote a rational synthesis of X-ray amorphous IrO<sub>x</sub> hydroxides that contain a favorable arrangement of structural units
for improved performance in catalytic water splitting