Enhanced reconstruction of Fe5Ni4S8 by implanting pyrrolidone to unlock efficient oxygen evolution

Abstract

During oxygen evolution reaction (OER), complex changes have been reported on surfaces of bimetallic Fe-Ni-based catalysts, and regulating the dynamic evolution could improve their electrocatalytic performances. Herein, a pyrrolidone-promoted reconstruction of pentlandite was investigated to uncover the correlation between the reconstructed surface and the OER performance. The theoretical calculations indicated the preferential implantation of pyrrolidone at Fe atoms, useful for regulating the electronic structures of pentlandite. The valence state of Ni increased, suggesting the promotion of the in-situ reconstruction of pentlandite via strengthening hydroxyl adsorption to generate highly active NiOOH. The electron-rich pentlandite was also found conducive to charge transfer under applied voltages. The Operando Raman and various quasi-in-situ characterizations confirmed the realization of more delocalized electronic structures of pentlandite by introducing pyrrolidone. This, in turn, promoted the accumulation of hydroxyl groups on the pentlandite surface, thereby boosting the formation of highly active NiOOH at lower OER potentials. Consequently, the adsorption energies of intermediates were optimized, conducive to enhanced OER reaction kinetics. As a proof of concept, the pentlandite decorated by pyrrolidone exhibited an overpotential as low as 265 mV at 10 mA cm−2 coupled with stable catalysis for 1000 hours at a high current density of 100 mA cm−2. In sum, new insights into unlocking the high catalytic activity of bimetallic Fe-Ni-based catalysts were provided, promising for future synthesis of advanced catalysts.