Heterophase stimulated active species evolution in iron/cobalt sulfide nanocomposites for oxygen evolution

Developing efficient and non-noble metal electrocatalysts for oxygen evolution reaction (OER) is crucial toward improving the efficiency of electrochemical energy conversion and storage devices. In this study, a series of Fe/Co-based sulfide nanocomposites were synthesized. The formed Fe/Co-based sulfide product exhibits excellent catalytic OER activity with the overpotential of 283 mV at 10 mA cm−2 in 1 M KOH and a Tafel slope of 92.7 mV dec−1. This catalyst also exhibits an excellent stability with continuous catalysis for at least 50 h; after OER operation for 50 h, the catalytic current density keeps almost constant. As revealed by characterization-contrast of the catalysts before and after OER, the catalyst surface is gradually transformed into MOOH species (M: Co, Fe), which were doped by some oxidized sulfur species. The interactions between Co and Fe, as well as the doping of oxidized sulfur species would optimize the binding state of intermediates (OH, OOH, and O) on cobalt/iron active sites, inducing the enhancement of catalytic activity. This work provides some insights for the design of sulfide electrocatalysts.