Flexible and Binder‐Free Iron Phosphide Electrodes Using a Three‐Dimensional Support for High Hydrogen Productivity

Abstract

In this work, an inexpensive and reliable microstructured electrode for the hydrogen evolution reaction (HER) is developed. This cathode is made of Earth‐abundant elements consisting of iron phosphide as an electrocatalyst and carbon felt (CF) as a flexible conductive scaffold. Its porous character and binder‐free FeP coverage over the carbon fibers generate a high number of accessible active sites for the reaction, achieving a high value of the electrochemically active surface area. The electrode reaches 100 mA ⋅ cm−2 by applying only −53 mV vs RHE at 50 °C in 0.5 M H2SO4, demonstrating excellent electrocatalytic activity for the HER and outstanding stability in acidic electrolyte. Furthermore, the feasibility of these electrodes for industrial application is evaluated using a PEM electrolyzer. The developed prototype with a cathodic area of 1.8 cm2 shows a very promising performance, reaching 14.9 mmol H2 ⋅ h−1 ⋅ cm−2 (corresponding to 800 mA ⋅ cm−2) at a voltage of only 2.1 V.