Central Idea

Researchers from IIT-Madras have developed components for a cost-effective method of electrolyzing seawater to produce green hydrogen.
The current alkaline water electrolyzer technology is energy-intensive, requires an expensive oxide-polymer separator, and uses fresh water.

Generating Green Hydrogen

Instead of using fresh water, the researchers developed an electrolyzer that utilizes alkaline seawater.
Carbon-based support material was used for the electrodes to minimize corrosion.
Transition metal-based catalysts were designed to catalyze both oxygen and hydrogen evolution reactions, improving the production of hydrogen and oxygen.
A cellulose-based separator was developed to allow hydroxide ions to pass through while preventing crossover of oxygen and hydrogen.

The alkaline water electrolyzer involves two half-reactions at the anode and cathode.
At the cathode, water dissociates into H+ and hydroxide ions, with H+ ions converting into hydrogen.
Hydroxide ions produced at the cathode pass through the separator, and oxygen is generated at the anode.
When seawater is used, hypochlorite formation occurs at the anode, causing corrosion and reducing oxygen production. Impurities also affect the hydrogen evolution reaction at the cathode.

The carbon-based support material was used for both anode and cathode electrodes to prevent corrosion.
The catalyst coating on the support material enhances hydrogen production at the cathode and oxygen production at the anode.
Transition bimetals in the catalyst are selective toward oxygen evolution reaction, overcoming the challenge of hypochlorite formation.
Despite impurities adsorbed on the cathode, the catalyst promotes hydrogen evolution, increasing hydrogen production.

The team developed a cellulose-based separator to separate the anode and cathode.
The separator allows hydroxide ions to pass through but minimizes the crossover of hydrogen and oxygen.
The separator shows high resistance to degradation in seawater.

The assembled electrolyzer achieved a seawater splitting voltage of 1.73 V at 10 mA/sq.cm and 26 degrees C.
The optimized parameters enable the electrolyzer to directly use photovoltaic-derived voltage for green hydrogen production.
Two prototypes of different dimensions were developed, producing hydrogen at rates of 250 ml/hour and 1 liter/hour.
A stack of three cells produced hydrogen at a rate of about 4 liters/hour.

	Production Method	Carbon Emissions
Gray Hydrogen	Steam Methane Reforming (SMR) from fossil fuels	High emissions
Blue Hydrogen	Steam Methane Reforming (SMR) from fossil fuels with carbon capture and storage (CCS) or carbon capture utilization and storage (CCUS)	Reduced emissions compared to gray hydrogen
Green Hydrogen	Electrolysis using renewable energy sources (solar, wind, hydro)	No carbon emissions
Turquoise Hydrogen	Methane pyrolysis from fossil fuels with carbon capture and storage (CCS) or carbon capture utilization and storage (CCUS)	Reduced emissions compared to gray hydrogen