NiFe Sulfide and Ti3C2 MXene Nanocomposites for High-Performance Seawater Electrolysis

 

Clean and sustainable energy sources are essential to address energy shortage and reduce carbon emissions caused by fossil fuels. One promising solution is the production of "green" hydrogen through water electrolysis using renewable energy sources such as solar and wind power.

The use of anion exchange membranes (AEM) has gained attention because it combines the low cost and high efficiency of alkaline water electrolysis with the benefits of proton exchange membrane (PEM) electrolysis, which is compatible with renewable energy sources.

However, freshwater is a limited resource, making direct seawater electrolysis an attractive alternative for future large-scale hydrogen production.  To date, satisfactory progress has not been made in obtaining systems based on anion exchange membranes. One major challenge is the development of highly stable electrocatalysts that can withstand both oxygen evolution reaction (OER) conditions and chloride-induced corrosion.

A research team in China developed a robust nanocomposite electrocatalyst by integrating MXene (Ti3C2) with Ni-Fe sulfides ((Ni,Fe)S2@Ti3C2). Using various characterizations and theoretical (DFT) calculations, they demonstrated that the strong interaction between (Ni,Fe)S2 and Ti3C2 regulates electron distribution, activating the OER. Additionally, the formation of Ti-O-Fe bonds prevents the loss of Fe species during the process, improving long-term stability. Additionally, the material effectively retains sulfates and features Ti3C2 groups that shield against chloride corrosion.

As a result, the (Ni,Fe)S2@Ti3C2 nanocomposite achieves high OER activity (1.598 V at 2 A cm-2) and remains stable for over 1,000 hours in seawater electrolysis. Moreover, when used as an anode along with a Ni Raney cathode (a nickel-based material with a porous structure that improves hydrogen production), the system operates at industrial current density (0.5 A cm-2) with 500 hours of durability, 70% efficiency, and an energy consumption of 48.4 kWh per kg of H2.

This study provides an effective methodology to address seawater electrolysis based on AEM technology, solving the challenges of catalyst degradation and chloride corrosion. 

More information in Nature Communications