Co3+-rich CoFe-PBA encapsulated in ultrathin MoS2 sheath as integrated core-shell architectures for highly efficient OER

Highly active and stable oxygen evolution reaction (OER) electrocatalyst is the key component of sustainable water splitting reaction. Controllable core-shell engineering is one of the most effective strategies for modulating the local electronic structure of active sites to enhance catalytic activity. Herein, we design a nano-cube of Co3+-rich CoFe Prussian blue analogues coated with controllable MoS2 shell heterostructures as OER electrocatalyst by simple solvothermal method, named as CoIIIFe-PBA/MoS2. Importantly, CoIIIFe-PBA/MoS2 possesses an extremely low overpotential of 306 mV at the current density of 100 mA cm−2, a small Tafel slope of 36.2 mV dec−1 and excellent stability for OER. The results of spectroscopic characterizations reveal that the Co3+ species with more 3d electron orbits origin from the charge transfer between CoFe-PBA and MoS2 core-shell interface, which promotes the electron accepting and results in the higher electrochemical activity. This research offers unique insight to design other advanced electrocatalysts with high-valent transition metal ions and core-shell structure.