Vanadium-Doped Heterogeneous Bimetallic Phosphides Derived from Layered Double Hydroxides for Saline Water Splitting

The development of energy- and time-saving synthetic methods to prepare bifunctional and high stability catalysts are vital for overall water splitting. Here, V-doped nickel-iron hydroxide precursor by etching NiFe foam (NFF) at room temperature with dual chloride solution ("NaCl-VCl3"), is obtained then phosphating to obtain V-Ni₂P-FeP/NFF as efficient bifunctional (oxygen/hydrogen exchange reaction, OER/HER) electrocatalysts, denoted as NFF(V, Na)-P. The NFF(V, Na)-P requires only 185 and 117 mV overpotentials to reach 10 mA cm^-2 for OER and HER. When used as a catalyst for water splitting in a full cell, it can be stably sustained for more than 1000 h in alkaline brine electrolysis at both current densities of 100 and 500 mA cm^-2. In situ Raman analyses and density functional theory (DFT) show that the V-doping-induced surface remodeling generates hydroxyl oxides as the true catalytic active centers, which not only enhances the reaction kinetics, but also reduces the free energy change in the rate-determining step. This work provides a cost-effective substrate self-derivation method to convert commercial NFF into a powerful catalyst for electrolytic brine, offering a unique route to the development of efficient electrocatalysts for saline water splitting.