Self-supported iron-based bimetallic phosphide catalytic electrode for efficient hydrogen evolution reaction at high current density

Iron (Fe)-based materials, which are abundant in Earth's crust, can be competent candidates as electrocatalysts for large-scale and sustainable alkaline hydrogen evolution reaction (HER); however, unlocking their huge potential critically relies on the rational integration of their structures and electrode materials. Herein, we report the construction of FeP-based bimetallic electrodes through a facile soaking-phosphorization approach. The hierarchical structure of porous iron foam (IF)-nanosheet arrays (NAs) endows enhanced reaction kinetics under high current densities. Modification with different transition metal cations evidently improves the intrinsic catalytic activity of FeP, among which cobalt-modified FeP (CoFe-P) shows the best performance. The optimized CoFe-P NAs/IF electrode exhibits an outstanding catalytic performance in the HER in alkaline media, with a current density of 10 mA cm-2 at an extremely low overpotential of 40 mV. Additionally, at high current densities of 500 and 1000 mA cm-2, the electrode requires impressively low overpotentials of 151 and 162 mV, respectively. Furthermore, the catalytic performance experiences minimal degradation after a stability test at 500 mA cm-2 for 200 hours, suggesting the exceptional stability of the CoFe-P NAs/IF electrode. Cheap Fe foam (IF) was entirely transformed to the robust and high output CoFe-P NAs/IF electrode via facile soaking-phosphorization approach. The as-prepared CoFe-P NAs/IF exhibits remarkable HER activity and stability under industrial conditions.