Hydrogen evolution under large-current-density based on fluorine-doped cobalt-iron phosphides

Abstract Developing the transition metal-based electrocatalysts for hydrogen evolution reaction (HER) under large-current-density is crucial for industrial electrolysis of water. However, most of reported HER electrocatalysts in alkaline solution are tested under the current density of less than 100 mA cm−2. In this work, CoFe Prussian blue analogues (PBA) supported on iron foam (IF) as precursor can (has been) be utilized to construct the fluorine-doped cobalt-iron phosphides (F-Co2P/Fe2P/IF). At the large-current-density at 100, 500, 1000 and 2000 mA cm−2, we systematically investigate the HER performance of F-Co2P/Fe2P/IF. Compared to the electrocatalyst without F− doping, F-Co2P/Fe2P/IF only need the low overpotential of 229.8, 260.5, 292.2 and 304.4 mV, respectively, when reaching the large current of 500, 1000, 2000 and 3000 mA cm−2. The F doping may induce the valence state and electronic structure of Co and Fe ions for enhanced HER activity. The role of F doping is furtherly analyzed by introducing barium ions as precipitation agent. At the same time, it can maintain for a long-term stability in 1.0 and 6.0 M KOH at the different high current density. The stableF-Co2P/Fe2P/IF may bear the high current density and high temperature during industrial water electrolysis. This work enables it possible at the large current density for industrial water splitting.