The groundbreaking discovery of insoluble anodes

Anodes- electrodes of the new DSA®s

In the 1970s, one of the most significant advancements in industrial chemistry was the development of the DSA® electrode technology. These metallic insoluble anodes significantly improved the energy efficiency of chlor-alkali processes. Specifically, DSA electrodes consist of a titanium base coated with a thin layer of mixed metal oxides (MMOs) that act as electrocatalysts for a wide variety of electrochemical processes, including the production of chlorine at the anode and formation of sodium hydroxide and hydrogen at the cathode of an electrochemical cell.

Before the breakthrough of DSA electrodes, carbon materials like graphite and amorphous carbon were used for the anodes, but they had several drawbacks. In fact, the theoretical voltage for the reactions for the chlor-alkali process based on thermodynamics (i.e., the reversible potentials of the anode and cathode) is slightly above 2.1 V. However, before the introduction of DSA, the actual voltage was nearly 5 V due to slow reaction kinetics, mass-transport limitations, and Ohmic losses, leading to high electricity consumption and increased production costs. Additionally, carbon anodes were highly susceptible to corrosion (as displayed in equation 1), causing additional increases in the voltage at the reactor over time and frequent interruption of the production process due to the necessary replacement of the anodes.

C + 2H2O → CO2 + 4H+ + 4e- (1)

Efforts to overcome these issues included two patents by Henri Bernard Beer, a Dutch industrial researcher, who investigated MMOs for the purpose of chlorine production in the chlor-alkali field. Later, Industrie De Nora bought the patents for the large-scale commercialization of the DSA® anodes. A disruption in the field of DSA anodes came with De Nora’s introduction of a new business model based on leasing the anodes rather than selling them directly. This new business model guaranteed the performance of a certain chlorine production over long periods of time without stopping operations, thus satisfying the needs of the demanding chlor-alkali industry.

DSA anodes possess mechanical stability, unlike their carbon counterparts. In areas where traditional electrocatalysts would undergo degradation, the titanium base forms a protective oxide layer, exhibiting a “self-healing property” specific to titanium. Notably, replacing carbon anodes with DSA insoluble anodes reduced the operating voltage by more than 1 V where catalyzed. Additionally, it provided stable electrode performance for many years of the operating life, marking a significant improvement in the industry compared to the traditional use of carbon-based anodes.

DSA® is a registered trademark of De Nora. Under the DSA® trademark, we offer a broad range of products consisting of metallic anodes and cathodes coated with catalytic mixed-oxide solutions for a variety of electrochemical reactions. DSA electrodes have a long operating life, ensure excellent electrolytic performance and cell efficiency, and enable significant energy savings and optimal operating conditions. Their light and stable design allows for easy handling and application in precise equipment, including those with zero electrode gap, while removing pollution problems derived from soluble or unstable anodes.

Applications of DSA electrodes

DSA electrodes are widely used in electrochemical processes due to their durability, high efficiency, and resistance to corrosion. Applications include, but are not limited to:

Electronics manufacturing (copper foil electrodeposition, PCB, Lithium-ion batteries)
Electrowinning (copper, nickel, cobalt)
Surface finishing, electroplating, electrogalvanizing
Chlor-alkali processes
Cathodic protection/ corrosion prevention (traditional, concrete and seawater installations)

Another application of DSA anodes is in the water treatment field. In fact, DSA are employed to oxidize organic and inorganic pollutants, transforming them into less harmful substances. They are particularly effective in advanced oxidation processes (AOPs) for degrading persistent organic pollutants, which are challenging to remove through conventional treatment methods. Finally, DSA electrodes have been finding applications in the emerging field of green hydrogen production, an electrochemical process whereby water is split into its constituents, oxygen and hydrogen.

Insoluble vs. soluble anodes

In conclusion, the introduction of DSA electrodes coincided with a growing demand for more efficient and environmentally friendly industrial processes. As industries sought to minimize waste and energy consumption, DSA provided a solution that aligned with these objectives, solidifying their place as a cornerstone of modern electrochemical technology. Today, the use of DSA continues to expand across a wide range of traditional electrochemical applications as well as others, like water treatment and purification, and green hydrogen production, driven by ongoing research and development aimed at enhancing their performance and sustainability.

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