Effect of Iron and Vanadium Doping on Structural Phase Transition in Cobalt Diselenide Enabling Superior Oxygen/Hydrogen Electrocatalysis

Clean energy technologies hold tremendous potential when noble-metal electrocatalysts are replaced with earth-abundant materials that are economical, highly effective, and long-term stable. In this study, we describe a dual-cation Fe, V-codoped electrocatalyst capable of structural change from orthorhombic cobalt selenide to monoclinic cobalt selenide (Co 3 Se 4 ) for three vital energy conversion schemes: oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER). A mesoporous CoSe 2 catalyst exhibits a favorable morphology for electrolyte transport and uninterrupted gas diffusion during catalysis. Therefore, the FeV-doped m-Co 3 Se 4 electrocatalysts achieved superior ORR/OER/HER performance, with an overpotential of 280 mV @ η 10 for the OER and 184 mV @ η 10 for the HER, and a low half-wave potential of 0.76 V for the ORR. Water-splitting devices assembled with FeV/ m -Co 3 Se 4 exhibit low voltages but long operating times (more than 30 h), comparable to iridium oxide (IrO 2 ) and Pt/C operating catalysts. Several defects associated with Fe and V dopants are investigated in this study to demonstrate their synergistic role in improving water-splitting.