Highly efficient overall-water splitting enabled via grafting boron-inserted Fe-Ni solid solution nanosheets onto unconventional skeleton

Abstract The aggregation of transition metal nanoparticles severely degrades their catalytic activity towards water splitting. Although this issue can be alleviated by the popular carbon-hybridization and metal foam-confinement strategies, the complicated fabrication procedure and the support corrosion parasitic in these strategies inevitably result in high usage cost and unsatisfactory cycle durability. Herein, we in-situ space-confined boron-inserted Fe-Ni solid solution nanosheets onto the activated hydrophilic sponge (B-FeNi@HS) via substitution of Fe by Ni and insertion of B within the Fe lattice interstitials in the presence of NH4+-modified dimethylamino borane solution. When served as the bifunctional electrocatalysts, B-FeNi@HS only needs overpotentials of 54 and 171 mV to afford 10 mA cm–2 for HER and OER in 1.0 M KOH, respectively. In addition, the alkaline overall-water splitting system constructed by using B-FeNi@HS as two-electrodes only delivers an ultralow cell voltage of 1.456 V to drive 10 mA cm–2, and shows negligible activity decay even at 500 mA cm–2 for 3 days. Such outstanding performance can be traced to the synergism of corrosion-resistant support, hierarchical morphology with favorable surface area and dual solid-solution crystal structure, ensuring robust mechanical stability, rapid charge/mass transfer kinetics as well as the energetically favorable formation of intermediates during catalysis. The proposed strategy is versatile and can be extended to synthesize other efficient B-inserted Fe-based electrocatalysts.