Highly efficient FeS2@FeOOH core-shell water oxidation electrocatalyst formed by surface reconstruction of FeS2 microspheres supported on Ni foam

FeS2 without dopants often exhibits poor oxygen evolution reaction (OER) performance, and development of FeS2 with excellent performance for OER is still a challenge. In this study, uniform FeS2 microspheres were synthesized and supported on Ni foam (NF), showing excellent OER activity with a low overpotential of 170 mV at 10 mA/cm2 in 1.0 M KOH electrolyte, superior to NF, other FeS2 on NF and most of Fe-containing non-noble metal OER catalysts in the existing literature (ranked top 4) under the same test conditions. The revealing of catalyst reconstruction during OER is essential for understanding the real active sites, but studies on FeS2 reconstruction are rare. Herein, reconstruction of FeS2 microsphere to core-shell FeS2@FeOOH during OER was observed using TEM, SEM, XRD, XPS and Raman spectroscopy. The special core-shell FeS2@FeOOH structure benefited the OER performance. This research has significance for the understanding and rational design of FeS2 catalyst for OER.