Fe/Co and Ni/Co-pentlandite type electrocatalysts for the hydrogen evolution reaction

Metal-rich transition metal sulfides recently gained increasing attention as electrocatalysts for the hydrogen evolution reaction (HER), as they are capable to overcome major challenges faced by sulfide-rich metal catalysts such as limited conductivity and the necessity of nanostructuring. Herein, we present the synthesis, characterization and electrocatalytic investigation of ternary metal-rich sulfide composites FexCo9-xS8 as well as NiyCo9-yS8 (x = y = 0-4.5), which possess pentlandite-type structures. In this study, we show a stepwise alteration of the binary cobalt pentlandite Co9S8 and report on the replacement of cobalt with up to 4.5 equivalents of either iron or nickel. These altered pentlandite composites facilitate the proton reduction in acidic media at different temperatures. We furthermore show that the stoichiometric variation has a decisive influence on the electrochemical activation/deactivation behavior of the catalysts under reductive electrocatalytic conditions. Here, Co-deficient composites display an improved HER performance in contrast to Co9S8. Notably, Ni/Co compounds generally tend to show higher catalytic activities towards HER than their respective Fe/Co compounds. (C) 2021, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

Metal-rich transition metal sulfides have gained attention as electrocatalysts for the hydrogen evolution reaction due to their ability to overcome challenges faced by sulfide-rich metal catalysts. This study demonstrates the synthesis, characterization, and electrocatalytic investigation of ternary metal-rich sulfide composites with pentlandite-type structures. Stoichiometric variation in these composites significantly influences their electrochemical activation/deactivation behavior, with Co-deficient composites showing improved performance in HER compared to Co9S8. Additionally, Ni/Co compounds generally exhibit higher catalytic activities towards HER than Fe/Co compounds.