Tailoring the Electrocatalytic Activity of Pentlandite FexNi9-XS8 Nanoparticles via Variation of the Fe : Ni Ratio for Enhanced Water Oxidation
The development of efficient and cost-effective electrocatalytic materials is an important part in scaling up sustainable electrochemical energy devices such as electrolyzers and fuel cells. In particular, the sluggish kinetics of the oxygen evolution reaction (OER) during water splitting renders the need of a catalyst indispensable. However, the development of catalysts is often based on laboratorial trial-and-error approaches and complex synthetic routes. Herein, the facile and systematic synthesis of pentlandite-like FexNi9-xS8 (x=0-9) nanosized particles from its elements with distinct Fe: Ni ratios was achieved using a mechanochemical method. The OER performance is optimized through tailoring the surface properties via altering the catalyst composition. The catalytic activity increases with higher nickel content in the structure, accomplishing an overpotential of 354 and 420 mV for 'Ni9S8' to drive 10 and 100 mA cm−2, respectively, with high stability. The in-situ formed nickel oxide/hydroxide species concurrent with sulphur depletion from the pentlandite structure upon OER are more active than NiS, inferring the crucial role of the pentlandite structure in activity. The herein reported simple synthetic approach could bring significant progress in the catalyst material development via rationally screening pentlandites with desired properties for modern energy systems.