Mild construction of an Fe-B-O based flexible electrode toward highly efficient alkaline simulated seawater splitting

It is essential to construct self-supporting electrodes based on earth-abundant iron borides in a mild and economical manner for grid-scale hydrogen production. Herein, a series of highly efficient, flexible, robust, and scalable Fe-B-O@FeB_x modified on hydrophilic cloth (denoted as Fe-B-O@FeB_x/HC, 10 cm × 10 cm) are fabricated by mild electroless plating. The overpotentials and Tafel slope values for the hydrogen and oxygen evolution reactions are 59 mV and 57.62 mV dec^-1 and 181 mV and 65.44 mV dec^-1, respectively; only 1.462 V is required to achieve 10 mA cm^-2 during overall water splitting (OWS). Fe-B-O@FeB_x/HC maintains its high catalytic activity for more than 7 days at an industrial current density (400 mA cm^-2), owing to the loosened popcorn-like Fe-B-O@FeB_x that is firmly loaded on a 2D-layered and mechanically robust substrate along with its fast charge and mass transfer kinetics. The chimney effect of core-shell borides@(oxyhydro)oxides enhances the OWS performance and protects the inner metal borides from further corrosion. Moreover, the flexible Fe-B-O@FeB_x/HC electrode has a low cost for grid-scale hydrogen production ($2.97 kg^-1). The proposed strategy lays a solid foundation for universal preparation, large-scale hydrogen production and practical applications thereof.