Seawater is one of the most abundant natural resources on our planet. Electrolysis of seawater is not only a promising approach to produce clean hydrogen energy, but also of great significance to seawater desalination. The implementation of seawater electrolysis requires robust and efficient electrocatalysts that can sustain seawater splitting without chloride corrosion, especially for the anode. Here we report a three-dimensional core-shell metal-nitride catalyst consisting of NiFeN nanoparticles uniformly decorated on NiMoN nanorods supported on Ni foam, which serves as an eminently active and durable oxygen evolution reaction catalyst for alkaline seawater electrolysis. Combined with an efficient hydrogen evolution reaction catalyst of NiMoN nanorods, we have achieved the industrially required current densities of 500 and 1000 mA cm⁻² at record low voltages of 1.608 and 1.709 V, respectively, for overall alkaline seawater splitting at 60 °C. This discovery significantly advances the development of seawater electrolysis for large-scale hydrogen production.

Developing highly active and low-cost electrocatalysts with superior durability for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is a grand challenge to produce hydrogen by electrolysis of water. Here, we report on a facile and scalable approach to fabricate highly efficient three-dimensional (3D) bulk catalysts of core–shell nanostructures, in which few-layer NiFe layered double hydroxide (LDH) nanosheets are grown on Cu nanowire cores supported on Cu foams, toward overall water splitting. Remarkably, benefiting from the 3D hierarchical nanoarchitecture with large surface areas, fast electron transport, and open-channels for effective gas release, the resulting 3D self-standing catalysts exhibit outstanding OER activity as well as excellent HER performance in an alkaline medium. Using them as bifunctional catalysts for overall water splitting, a current density of 10 mA cm⁻² was achieved at a voltage of 1.54 V, and 100 mA cm⁻² at 1.69 V with excellent durability, which is much better than the benchmark of IrO₂(+)//Pt(−) electrodes. Our 3D core–shell electrocatalysts significantly advance the research towards large-scale practical water electrolysis.

Developing energy- and time-saving methods to synthesize active and stable oxygen evolving catalysts is of great significance to hydrogen production from water electrolysis, which however remains a grand challenge. Here we report a one-step approach to grow highly porous S-doped Ni/Fe (oxy)hydroxide catalysts on Ni foam in several minutes under room temperature. This ultrafast method effectively engineers the surface of Ni foam into a rough S-doped Ni/Fe (oxy)hydroxide layer, which has multiple levels of porosity and good hydrophilic features and exhibits extraordinary oxygen evolution reaction (OER) performance in both alkaline salty water and seawater electrolytes. Specifically, the S-doped Ni/Fe (oxy)hydroxide catalyst requires low overpotentials of 300 and 398 mV to deliver current densities of 100 and 500 mA cm⁻², respectively, when directly used as an OER catalyst in alkaline natural seawater electrolyte. Using this OER catalyst together with an efficient hydrogen evolution reaction catalyst, we have achieved the commercially demanded current densities of 500 and 1000 mA cm⁻² at low voltages of 1.837 and 1.951 V, respectively, for overall alkaline seawater electrolysis at room temperature with very good durability. This work affords a cost-efficient surface engineering method to steer commercial Ni foam into robust OER catalysts for seawater electrolysis, which has important implications for both the hydrogen economy and environmental remediation.

Splitting water into hydrogen and oxygen by electrolysis using electricity from intermittent waste heat, wind, or solar energies is one of the easiest and cleanest methods for high-purity hydrogen production and an effective way to store the excess electrical power. The key dilemma for efficient large-scale production of hydrogen by splitting of water via the hydrogen and oxygen evolution reactions (HER and OER, respectively) is the high overpotential required, especially for the OER. We report an exceptionally active and durable OER catalyst yielding current densities of 500 and 1000 mA cm⁻² at overpotentials of only 259 mV and 289 mV in alkaline electrolyte, respectively, fulfilling the commercial criteria of the OER process. Together with a good HER catalyst, we have achieved the commercially required current densities of 500 and 1000 mA cm⁻² at 1.586 and 1.657 V, respectively, with very good stability, dramatically lower than any previously reported voltage. This discovery sets the stage for large-scale hydrogen production by water splitting using excess electrical power whenever and wherever available.