3D Hierarchical Porous Fe/Ni-P-B as Practical Bifunctional Electrode for Alkaline Water Electrolysis

Bifunctional electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are extremely attractive as they can simplify the water electrolysis system. Here, a general and scalable strategy to prepare stable and efficient bifunctional electrode was reported, based on a novel hierarchical porous structure constructed by conductive electrocatalyst. The method involved the construction of 3D monolithic structure and its surface reconstruction by chemical etching process. This strategy produced an advanced 3D hierarchical porous Fe/Ni-P-B@MS electrode containing well-defined macropores (>100 μm) at the inter-wire space and mesopores (<100 nm) distributed uniformly over the entire catalyst surface. This highly efficient bifunctional electrode required only 79 and 279 mV to reach 100 mA cm^-2 toward HER and OER in 1.0 m KOH. An alkaline electrolyzer consisting of this electrode provided 100 mA cm^-2 at a low cell voltage of 1.61 V and survived at large current density of 800 mA cm^-2 for over 140 h without apparent degradation. This work provides a new perspective for the rational design of transition metal-based bifunctional electrodes with outstanding performance.