  Nickel-iron layered double hydroxide (NiFe LDH) platelets with high
morphological regularity and sub-micrometre lateral dimensions were synthesized
using a homogeneous precipitation technique for highly efficient catalysis of
the oxygen evolution reaction (OER). Considering edge sites are the point of
activity, efforts were made to control platelet size within the synthesized
dispersions. The goal is to controllably isolate and characterize size-reduced
NiFe LDH particles. Synthetic approaches for size control of NiFe LDH platelets
have not been transferable based on published work with other LDH materials and
for that reason, we instead use post-synthetic treatment techniques to improve
edge-site density. In the end, size reduced NiFe LDH/single-wall carbon
nanotube (SWCNT) composites allowed to further reduce the OER overpotential to
237 plus/minus 7 mV ( L = 0.16 plus/minus 0.01 micrometres, 20 wt% SWCNT),
which is one of the best values reported to date. This approach as well
improved the long term activity of the catalyst in operating conditions.
