Developing
highly active oxygen evolution reaction (OER) electrocatalysts
is crucial and highly desirable to improve the efficiency of water
electrolysis for H2 fuel generation. In this work, hierarchical
MoO4
2– intercalating α-Co(OH)2 nanosheet assemblies were synthesized from the readily available
metal source and 2-methylimidazole as the alkaline reagent by green
and fast coprecipitation. The ultrathin α-Co(OH)2-MoO4(25) nanosheets possess a lateral size of about 40–100
nm and a thickness from 2.5 to 4.6 nm (3 to 6 layers). Triggered by
OER oxidation treatment, the α-Co(OH)2-MoO4(25) material undergoes ultrafast and thorough structure reconstruction
to CoOOH(25) by only one linear sweep voltammetry scan and chronopotentiometry
within 35 s. The in situ transformation leads to
the formation of the CoOOH active phase with rich oxygen vacancies
and distorted structure, extracting MoO4
2– ions at the same time. Compared with other designed counterparts,
CoOOH(25) offers a lower overpotential (309 mV) for the OER at a current
density of 10 mA cm–2 and a smaller Tafel slope
of only 57.78 mV dec–1, representing an excellent
unary CoOOH-based or Co(OH)2-based catalyst. The improved
catalytic activity of CoOOH(25) can be attributed to its specific
structures, e.g., ultrathin disordered nanosheets that could facilitate
electrolyte transportation and expose more active sites, oxygen vacancies
that enhance the intrinsic per-site activity, and their synergistic
effect. This established structure self-renewal technology might also
be expanded to other advanced nanomaterials toward other electrochemical
energy conversion processes.