In Situ-Grown Cobalt–Iron Phosphide-Based Integrated Electrode for Long-Term Water Splitting under a Large Current Density at the Industrial Electrolysis Temperature

Developing effective, stable, and economical electrocatalysts to achieve highly efficient overall water splitting under a large current density in industries is critical for renewable H 2 production. Here, benefiting from one-step preoxidation that makes Co foam to act not only as a conductive collector but also as the sole cobalt source, a seamless integrated electrode (Fe 2 P-Co 2 P/CF) is successfully synthesized in which Co 2 P, Fe 2 P, and Co foam are tightly connected by chemical bonds to construct a versatile, highly active, and a durable catalyst for water splitting in an alkaline medium. Such an electrode only requires 145, 208, and 254 mV for hydrogen evolution reaction (HER), while it requires 243, 291, and 317 mV for oxygen evolution reaction (OER) to deliver current densities of 100, 500, and 1000 mA cm –2, respectively. Notably, using Fe 2 P-Co 2 P/CF as both an anode and a cathode at room (25 °C) and quasi-industrial (65 °C) temperatures, the operating voltages are as low as 1.87 and 1.71 V to reach 500 mA cm –2, respectively, together with excellent long-term durability over 300 h. The prominent performance is due to the robust in situ growth together with the formation of a strongly coupled heterojunction between Fe 2 P and Co 2 P, making it one of the most potential candidates to meet the large-scale application of industrial water electrolysis.