Chemical transformation approach for high-performance ternary NiFeCo metal compound-based water splitting electrodes

Developing high-efficiency and cost-efficient electrodes for hydrogen and oxygen evolution reactions (HER and OER respectively) is a major challenge in water electrolysis technology. We developed a chemical transformation route that can produce both high-performance OER and HER electrodes by corrosion of a Ni foam and subsequent phosphidation process, which generated ternary NiFeCo layered double hydroxide (LDH) and phosphide nanosheets supported on the foam, respectively. Because of their compositions and high electrical conductivities, these ternary LDH and phosphide electrodes exhibited remarkably high activities for OER and HER, respectively, outperforming most of other catalysts reported to date. An alkaline water electrolyzer based on these electrodes achieved a current density of 10 mA/cm2 at an only 1.47 Vcell. In addition, anion exchange membrane water electrolyzer based on these electrodes reached a current density of 500 mA/cm2 at an only 1.75 Vcell.