Ultrafine Co:FeS₂/CoS₂ Heterostructure Nanowires for Highly Efficient Hydrogen Evolution Reaction

Developing cost-effective and non-precious-metal electrocatalysts is a major challenge in water-splitting applications but is important to realize renewable energy systems. Herein, we report an electrocatalyst for the hydrogen evolution reaction (HER) composed of ultrafine cobalt-doped iron sulfide/cobalt sulfide (Co:FeS2/CoS2) heterostructured nanowires (NWs), which were prepared by a facile hydrothermal route. In the HER, the Co:FeS2/CoS2 NWs achieved a low overpotential of 69 mV at 10 mA cm–2 and a Tafel slope of only 46 mV dec–1. The overpotential shifted by about 3 mV over 1000 cycles along with a slight change in morphology of the Co:FeS2/CoS2 NWs. Density functional theory calculations and experimental results revealed that the charge transport kinetics of the FeS2/CoS2 heterostructure contributed substantially to the high performance of this HER electrocatalyst. These ultrafine Co:FeS2/CoS2 NWs represent a promising alternative to platinum-based electrocatalysts for water splitting.