The assessment of OER activities were performed on the Autolab PGSTAT302N with an impedance module electrochemistry workstation. An Ag/AgCl (3 M KCl) electrode was used as the reference electrode, and a graphite rod was used as the counter electrode. The bulk Co3Sn2S2 single crystal was attached to a Cu wire with silver paint and served as the working electrode and catalyst. The LSVs were recorded with a scan rate of 5 mV/s. The electrochemical impedance spectroscopy was carried out with a 10-mV AC potential from 20 kHz to 0.01 Hz for correcting the polarization curves. All potentials were referenced to a reverse hydrogen electrode.