Strong Electron Interaction at the Amorphous/Crystalline Interface Enables Advanced Oxygen Evolution Reaction

Abstract

Incorporating amorphous and crystalline components is undoubtedly a strategy to learn from each other's strengths and complement each other's weaknesses for advanced electrocatalysts. Here, an efficient and stable oxygen evolution reaction (OER) catalyst with an amorphous/crystalline interface is reported. Specifically, a rapid coprecipitation approach is proposed to load amorphous FePO 4 nanoparticles onto crystalline NH 4 CoPO 4 •H 2 O nanosheets, resulting in a fascinating amorphous/crystalline interface. The prominent coupled effect between FePO 4 and NH 4 CoPO 4 •H 2 O is afforded by the interfacial phosphates, which build efficient channels to transfer electrons from Co to Fe. Besides the unique electronic structure, the coupled amorphous/crystalline hybrid facilitates the formation of highly active Co intermediates and accelerates the reaction kinetics and charge transport. Detailed electrochemical characterization reveals that this advantageous interface structure results in a notable decrease in the overpotential of the OER compared to materials with an amorphous phase or crystalline phase alone. The FePO 4 /NH 4 CoPO 4 •H 2 O hybrid exhibits a small overpotential of only 230 mV to achieve a current density of 10 mA cm −2 in 1 M KOH and 220 mV at 1 mA cm −2 in 0.1 M phosphate-buffered solution (PBS), which are much lower than the corresponding values of the pristine ones. It is envisioned that the highly operable amorphous−crystalline interface may open up new opportunities in rational design for advanced electrocatalysts.