- IIT-Madras researchers have developed components for a low-cost process of electrolyzing saltwater to produce green hydrogen.
- The existing technology for alkaline water electrolyzers is energy-intensive, requires an expensive oxide-polymer separator, and uses fresh water.
Green Hydrogen Production
- Rather than utilising fresh water, the researchers created an electrolyzer that uses alkaline saltwater.
- To reduce corrosion, the electrodes were supported by a carbon-based substance.
- Transition metal-based catalysts were developed to catalyse both oxygen and hydrogen evolution processes, hence boosting hydrogen and oxygen production.
- A cellulose-based separator was created to allow hydroxide ions to pass through while prohibiting oxygen and hydrogen crossover.
How does electrolysis work?
- Two half-reactions occur at the anode and cathode of the alkaline water electrolyzer.
- Water dissociates into H+ and hydroxide ions near the cathode, with the H+ ions changing to hydrogen.
- The separator separates the hydrogen ions produced at the cathode from the oxygen produced at the anode.
- When saltwater is utilised, hypochlorite is formed at the anode, which causes corrosion and reduces oxygen generation. Impurities also have an impact on the cathode’s hydrogen evolution reaction.
How did the Catalyst and Electrode come to be?
- To prevent corrosion, the carbon-based support material was employed for both the anode and cathode electrodes.
- The catalyst coating on the support material increases cathode hydrogen production and anode oxygen production.
- The catalyst’s transition bimetals are selective for oxygen evolution reactions, overcoming the issue of hypochlorite production.
- Despite the presence of contaminants on the cathode, the catalyst enhances hydrogen evolution, resulting in increased hydrogen generation.
What distinguishes this device?
- To separate the anode and cathode, the team created a cellulose-based separator.
- The separator allows hydroxide ions to pass through while limiting hydrogen and oxygen crossover.
- In seawater, the separator is highly resistant to deterioration.
Performance and Experimental Results
- At 10 mA/sq.cm and 26 degrees C, the built electrolyzer obtained a seawater splitting voltage of 1.73 V.
- The optimised parameters allow the electrolyzer to produce green hydrogen straight from solar voltage.
- Two prototypes of varying sizes were created, each capable of producing hydrogen at rates of 250 ml/hour and 1 liter/hour.
- A three-cell stack produced hydrogen at a rate of roughly 4 litres per hour.
Source: https://www.thehindu.com/sci-tech/science/iit-madras-generates-hydrogen-from-seawater-using-solar-energy/article66951534.ece#:~:text=Researchers%20from%20the%20Department%20of,journal%20ACS%20Applied%20Energy%20Materials.