Characterization and OER test dataset of NiS2 coupling with ferrous phosphite and phosphide

Powder X-ray diffraction (PXRD) patterns were obtained on a Philips X'pert Pro X-ray diffractometer with Cu Ka radiation (λ=0.15419 nm). Field emission scanning electron microscopy (FESEM) was performed on a Sirion 200. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) were performed on a Tecnai G2 F20. X-ray photoelectron spectroscopy (XPS) tests were performed with Al Ka X-rays on a Thermo VG Escalab 250 photoelectron spectrometer. Inductively coupled plasma-mass spectrometry (ICP-MS) was conducted on a Thermo Scientific iCAP6300. Raman measurements were performed with a 532 nm excitation wavelength on a Raman spectrometer (Renishaw inVia Reflex).Electrochemical tests were performed in a standard three-electrode system using 1 M KOH as the electrolyte with a CHI 750E electrochemical workstation at room temperature. A graphite rod (with a diameter of 6 mm) was used as the counter electrode, a Ag/AgCl electrode was used as the reference electrode and the as prepared catalyst coating on carbon paper was employed as the working electrode. The OER catalytic activity was gained by using linear sweep voltammetry (LSV) with a scan rate of 5 mV s-1 and the Tafel slope was calculated from the LSV data. Electrochemical impedance spectroscopy (EIS) was performed with a frequency from 100 kHz to 0.1 Hz at a constant potential. Long-term stability tests were performed by cyclic voltammetry scans at a sweep rate of 10 mV s-1 for 2500 cycles, chronoamperometry measurements at an h of 220 mV for 160 h and chronopotentiometry tests at a current density of 10 mA cm-2 for 130 h. All test data were iR-compensated (95%) and not otherwise specified. All measured potentials vs. the Ag/AgCl electrode were switched to the potentials vs. RHE using the following Nernst equation: ERHE = EAg/AgCl + 0.0591pH + 0.197 V.