Phosphide-based
electrocatalysts exhibit high activities in alkaline
solution toward overall water electrolysis. However, their real phases
during catalysis have not been comprehensively identified, leading
to improper advancement in material recognition and theoretical simulation.
In this work, in situ spatially coherent transmitted X-ray diffraction
and X-ray absorption spectroscopy were developed to probe Fe-doped
cobalt phosphides, presenting superior catalytic activity and reaction
kinetics for overall water electrolysis compared to pristine cobalt
phosphides. The results showed that Fe dopants latched the crystallographic
sites and stabilized the phosphide phase, which are the active species
for hydrogen evolution reaction, while pristine cobalt phosphide transformed
into hydroxides that impede the formation of active substances. Besides,
Fe-doped cobalt phosphides swiftly converted into active-site confined
oxyhydroxide for oxygen evolution reaction, achieving superb overall
catalytic performance. The genuine materials unveiled during the electrocatalysis
suggest that the appropriate catalytic mechanism correlates with the
phase transition and crystalline transformation rate.
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