The multi-redox mechanism involving multi-sites has great
implications
to dictate the catalytic water oxidation. Understanding the sequential
dynamics of multi-steps in oxygen evolution reaction (OER) cycles
on working catalysts is a highly important but challenging issue.
Here, using quasi-operando transient absorption (TA) spectroscopy
and a typical photosensitization strategy, we succeeded in resolving
the sequential oxidation kinetics involving multi-active sites for
water oxidation in OER catalytic cycle, with Co3O4 nanoparticles as model catalysts. When OER initiates from fast oxidation
of surface Co2+ ions, both surface Co2+ and
Co3+ ions are active sites of the multi-cobalt centers
for water oxidation. In the sequential kinetics (Co2+ →
Co3+ → Co4+), the key characteristic
is fast oxidation and slow consumption for all the cobalt species.
Due to this characteristic, the Co4+ intermediate distribution
plays a determining role in OER activity and results in the slow overall
OER kinetics. These insights shed light on the kinetic understanding
of water oxidation on heterogeneous catalysts with multi-sites.
Reaction sites, surface states and surface loaded electrocatalyst are photoinduced charge storage sites and critical to photoelectrochemical (PEC) performance, while the charge transfer mechanisms involved in the three remain poorly...
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