Heteroatom Ni alloyed pyrite-phase FeS2 as a pre-catalyst for enhanced oxygen evolution reaction

Highly active and low-cost electrocatalysts toward oxygen evolution reaction are urgently-needed in the field of energy conversion. Previous works have demonstrated that pyrite-phase sulfides are promising electrocatalysts for oxygen evolution reaction, however the true active materials are still undetermined. Here, we report heteroatom Ni alloying into FeS2 crystal via a facile ball-milling reaction method to enhance electrocatalytic performances of pyrite-phase FeS2. A series of (Fe1-xNix)S2 nanocrystalline materials are synthesized to systematically investigate the effects of Ni alloying on FeS2 toward oxygen evolution reaction electrocatalysis. To achieve an current density of 10 mA cm−2, the (Fe0.5Ni0.5)S2 at carbon fiber paper electrode requires an overpotential as low as 241 mV with a Tafel slope of 51.8 mV dec−1 in 1 M KOH solution. Further investigations reveal that the derived hybrids of Fe3O4 nanoflakes and nanoporous Ni doped FeOOH are true active materials for the (Fe0.5Ni0.5)S2 under oxygen evolution reaction conditions. This study not only reveals the true active materials of the heteroatom alloyed bimetallic sulfides, but also provides a facile strategy to regulate the formation of active materials for enhanced oxygen evolution catalysis.