Sea urchin-like Ni-Fe sulfide architectures as efficient electrocatalysts for the oxygen evolution reaction

Exploring highly efficient and cost-effective electrocatalysts for the oxygen evolution reaction (OER) is becoming increasingly important in the field of sustainable energy systems. In this work, a three dimensional (3D) hierarchical porous nickel and iron based sulfide (Ni-Fe-S) with a sea urchin-like morphology is synthesized by a facile sulfurization of Prussian blue analogue (PBA) precursors with a hydrothermal reaction and post-calcination treatment. The mass ratio of PBA and sulfur sources, the hydrothermal temperature and time, and the presence of hydrazine hydrate are found to be important factors for the formation of the unique sea urchin-like materials with the porous carbon layer and mixed phases of Fe5Ni4S8 and NiS, which are conducive to fast mass and charge transfer along various directions, endow the materials with mixed valences, improve the electronic conductivity and prevent the agglomeration of nanostructured sulfides. Benefiting from these fascinating advantages, the optimal Ni-Fe-S catalyst exhibits excellent catalytic activities with an overpotential as low as 200 mV to attain a current density of 10 mA cm(-2) and good stability toward the OER. This work not only offers a facile strategy to prepare efficient transition metal based sulfides with excellent electrocatalytic activity for the OER but also extends the synthesis and application of PBA-derived nanostructured materials.