Interfacial engineering of Ni3B/Co4B heterostructures for enhanced Electron transfer and bifunctional water/seawater splitting

Transition metal borides have attracted considerable attention as promising electrocatalysts for water electrolysis due to their high electrical conductivity and distinctive electronic structures. In this study, a NiCoMoO-B-NF catalyst featuring a Ni 3 B/Co 4 B heterostructure was in situ synthesized via boronizing of NiCoMoO 4 as the precursor. At the heterointerface, Ni sites with a significantly downshifted d-band center preferentially catalyze hydrogen desorption, whereas Co sites facilitate water dissociation. This bifunctional synergy substantially enhances HER kinetics. The boronizing process etched the precursor, generating a porous structure and exposing additional active sites. Moreover, boron promoted the reconstruction of metal sites during the oxygen evolution reaction (OER). The Mo component was partially dissolved as MoO 4 2− during OER and synergistically interacted with the generated B(OH) 4 − to form a dynamic protective layer, thereby improving the catalyst's resistance to Cl − corrosion in alkaline seawater. The NiCoMoO-B-NF catalyst exhibited low overpotentials of 169 mV for HER and 298 mV for OER at 100 mA cm −2 in 1 M KOH, with durability exceeding 110 h. In alkaline real seawater, slightly higher overpotentials of 175 mV for HER and 301 mV for OER were observed at the same current density, while good long-term stability was maintained. Furthermore, a two-electrode electrolyzer employing this bifunctional catalyst required only 1.95 V to achieve 500 mA cm −2 for overall water splitting, demonstrating its practical potential for seawater electrolysis. This work provides insights into the design of efficient and stable transition metal boride heterostructures for water and seawater electrolysis.