Trimetallic NiFeMo for Overall Electrochemical Water Splitting with a Low Cell Voltage

We report the development of an efficient and earth-abundant catalyst for electrochemical overall water splitting. Trimetallic NiFeMo alloy is synthesized by hydrothermal deposition from inorganic precursors and subsequent low-temperature thermal annealing. A complete cell made of NiFeMo electrodes on nickel foam exhibits a low voltage of 1.45 V at 10 mA/cm2 as a result of low overpotentials for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). High-resolution transmission electron microscopy reveals that nanometer-sized single-crystal domains of Ni, Fe, and Mo are intimately integrated at the atomic level, which enables a synergistic effect of metallic Ni, Fe, and Mo for efficient HER, while self-formed Ni–Fe–Mo (oxy)hydroxides on the surface of the NiFeMo anode become active sites for OER. Such a multimetallic alloy and its (oxy)hydroxides represent a typical HER/OER catalyst couple, and our method provides a new route to develop efficient low-cost metallic alloys for overall water splitting.