Electrodes for water electrolysis: electrocatalytic coatings

The importance of water electrolysis

Water electrolysis for green hydrogen production is essential to achieving a successful energy transition, decarbonizing the energy sector, and meeting net-zero emissions targets by 2050.

Unlike blue or grey hydrogen, green hydrogen requires an electrochemical process involving an anode and a cathode – the electrodes - separated by a membrane or diaphragm.
By applying an electric current to these electrodes, water is transformed into hydrogen at the cathode, whereas it is converted into oxygen at the anode (see equation below):

The efficiency challenge

In theory, water splitting occurs at an electrochemical potential of ΔE° = -1.23 V.
However, practical conditions rarely achieve this potential due to the overpotential required to drive the reaction.
Overpotential increases the electric current necessary to initiate water electrolysis, making it a critical factor in the efficiency of the process.

De Nora's innovative approach

De Nora is actively engaged in ongoing research aimed at developing high-performance electrodes for water electrolysis technologies.
This research focuses on designing electrodes that minimize overpotential and facilitate water splitting at an electrochemical potential the closest to ΔE° = - 1.23 V.

Achieving this is essential for creating efficient systems suitable for large-scale production and commercialization of green hydrogen.
In industrial applications, a lower electrochemical potential results in reduced energy requirements for hydrogen production.

Design and durability of electrocatalytic coatings

To achieve a lower electrochemical potential, De Nora scientists employ a tailored approach by developing electrocatalytic coatings to apply on a metal substrate, typically nickel, in the context of alkaline water electrolysis.

Several key considerations come into play during the development of these electrochemical coatings. Given the highly corrosive nature of the environment in alkaline water electrolysis (5.0 M NaOH/KOH), materials must withstand these harsh conditions without undergoing degradation. Research efforts are directed toward identifying the most suitable materials for electrocatalytic coatings, considering the limited number of elements that can endure such challenging experimental conditions.

Furthermore, the coatings must exhibit robustness to sustain long-term water electrolysis processes (up to 8 years). Thus, the system's durability becomes a crucial criterion for assessing the performance of the new electrode.

Optimizing coating application

The development of effective electrodes involves more than determining the metal coating formulation. Detailed and customized studies focus on how the coating should be applied to the electrode to achieve stability and sustained performance over time.

For example, the substrate, typically nickel, may require pretreatment before application or post-application treatment may be necessary.
This may involve the use of interlayers and protective layers, depending on the specific application and the robustness required for the active electrocatalytic coating.

Exploring new formulations and techniques

Creating new electrodes for water electrolysis presents its own set of challenges, and De Nora scientists are actively working to explore novel coating formulations and application techniques.

The ultimate goal is to align the electrochemical potential of these new and improved electrodes as closely as possible with the ideal thermodynamic value of ΔE° = -1.23 V, thereby minimizing the energy required for green hydrogen production.