As the world transitions towards a low-carbon future, the role of hydrogen as an energy storage solution has the potential to decarbonize many industries and to support economic growth as a new export market. The challenge, however, is to reduce hydrogen-water-climate nexus pressures.
Hydrogen has been described as the fuel for the 21st Century with many uses including for heating and cooking and for replacing diesel and petrol to power electric trucks, trains, and cars.
Hydrogen production dominated by fossil fuels
Demand for hydrogen has grown more than threefold since 1975 and continues to rise. This demand has been met nearly entirely from hydrogen production involving fossil fuels, with 6% of global natural gas and 2% of global coal used in its production. This has resulted in hydrogen production-related CO2 emissions of around 830 million tons of carbon dioxide per year, equivalent to the CO2 emissions of the United Kingdom and Indonesia combined.
Enormous water requirements
Hydrogen production requires significant amounts of high-quality water. It is estimated that every kilogram of hydrogen produced requires 9 kilograms of water, both in the electrolysis (consumption of water) and in the fuel cell (production of water). In Australia, to produce enough hydrogen to replace the 39 million tons of imported diesel and petrol fuel used by some of the nation’s industries each year would require an additional 99 GL of water, equivalent to an extra 1.7 million people living in the cities.
Producing hydrogen from seawater
To reduce hydrogen-water-climate nexus pressures, Stanford University scientists have recently found a new way of separating hydrogen and oxygen gas from seawater via electricity. In the electrolysis process, a power source connects to two electrodes placed in water. When the power turns on, hydrogen gas is released out of the negative end, the cathode, and oxygen emerges from the positive end, the anode. However, negatively charged chloride in seawater salt can corrode the positive end, limiting the system’s lifespan.
The scientists studied ways of stopping the seawater components from breaking down the submerged anodes and found that if they coat the anode with layers rich in negative charges, the layers repelled chloride and slowed down the decay of the underlying metal. Specifically, the team layered nickel-iron hydroxide on top of nickel sulfide, which covers a nickel foam core. The nickel foam acts as a conductor and the nickel-iron hydroxide sparks the electrolysis. During electrolysis, the nickel sulfide evolves into a negatively charged layer that protects the anode, with the negatively charged layer repelling chloride and preventing it from reaching the core metal. Without the coating, the anode only works for around 12 hours in seawater, but with this layer, it can work for more than a thousand hours.
Efficient, solar-powered hydrogen production
Previous attempts at splitting seawater for hydrogen fuel had used low amounts of electric current, as corrosion occurs at higher currents, but the Stanford researchers were able to conduct up to 10 times more electricity through their multi-layer device, which helps generate hydrogen from seawater at a faster rate. Furthermore, the team designed a solar-powered demonstration machine that produced hydrogen and oxygen gas from seawater collected from San Francisco Bay, with the machine operating at electrical currents that are the same as what is used in industry today.
The use of seawater and renewable energy sources is key to reducing hydrogen-water-climate nexus pressures.