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

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 boroninserted 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 overallwater 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.

Automated summary

The introduction of boron into Fe-Ni solid solution nanosheets to form B-FeNi@HS greatly enhances the catalytic activity for water splitting, with excellent stability and high efficiency.