A facile sequential ion exchange strategy to synthesize CoSe₂/FeSe₂ double-shelled hollow nanocuboids for the highly...

Transition metal-based nanostructures have been considered as promising substitutes for rare-earth metal oxide electrocatalysts toward the oxygen evolution reaction (OER). Herein, we report for the first time on a novel multicomponent metal selenide electrocatalyst based on CoSe2/FeSe2 double-shelled hollow nanocuboids (CoSe2/FeSe2 DS-HNCs) with the highly oxidative Co3+ species, which is synthesized via a facile sequential ion exchange strategy. The solid Co-precursor nanocuboids are first converted into the intermediate Co2[Fe(CN)6] with a mesoporous and double-shelled hollow structure produced through a facile ligand exchange at room temperature, and then the final CoSe2/FeSe2 DS-HNCs are obtained by a subsequent Se ion exchange reaction. The intermediate product of Co2[Fe(CN)6] plays an important role not only in constructing a double-shelled hollow structure but also in providing the Fe source for the growth of the final multicomponent metal selenides. Benefiting from the nanosized double-shelled hollow structure and mesoporous double-metal selenide shells with the highly oxidative Co3+ species, the as-prepared CoSe2/FeSe2 DS-HNCs exhibit superior OER performance to state-of-the-art metal selenides, including a small overpotential of 240 mV at a current density of 10 mA cm-2 and the excellent electrochemical durability over 50 h. This work opens up a new avenue towards developing highly active multicomponent noble-metal-free electrocatalysts.