Heterostructure engineering of the Fe-doped Ni phosphides/Ni sulfide p-p junction for high-efficiency oxygen evolution

Regulating charge distribution through heterostructure engineering is an encouraging approach to achieving efficient alkaline water electrolysis. Here, a Fe-doped Ni phosphides/Ni sulfide p-p heterojunction (NiFe-PS) for oxygen evolution reaction (OER) is constructed on nickel foam. It is shown that the built-in electric field at the interface of Fe-doped Ni phosphides/Ni sulfide facilitates the charge transfer and modifies the electronic properties of the catalyst, thereby enhancing its conductivity and catalytic activity. Profiting from the rational electronic structure modulation, the designed NiFe-PS electrode possesses excellent OER performance among phosphides with low overpotentials of 204 and 256 mV at current densities of 10 and 100 mA cm^-2, respectively. Meanwhile, the prepared catalyst displays high stability in the long-term chronopotentiometric test (125 h @ 100 mA cm^-2). Structural characterizations confirm that the outer phosphide layer can withstand long-term surface oxidation and operate as a robust shield to prevent oxidation of the inner sulfide, ensuring rapid electron transport within the catalyst throughout the OER process.