Researchers at Stanford University (Stanford, California, USA) have devised a new method to generate hydrogen fuel using solar power, electrodes, and salt water from the San Francisco Bay. They say the new method minimizes the risk of corrosion from salts, which has limited previous attempts to split seawater for hydrogen fuel when using electricity.
According to the researchers, hydrogen is an appealing option for fuel because it doesn’t emit carbon dioxide (CO2) and produces only water when burned.
Conceptually, they explain that splitting water into hydrogen and oxygen with electricity—called electrolysis—is nothing new. In this process, a power source connects to two electrodes that are placed in water. When power turns on, hydrogen gas bubbles out of the negative end—the cathode—and breathable oxygen emerges at the positive end—the anode. But negatively charged chloride in seawater salt can corrode the positive end, limiting the system’s lifespan.
In their work, the researchers discovered that if they coated the anode with layers rich in negative charges, the layers repelled chloride and slowed down the decay of the underlying metal.
They layered nickel-iron hydroxide on top of nickel sulfide (NiS), which covers a nickel foam core. The nickel foam acts as a conductor—transporting electricity from the power source—and the nickel-iron hydroxide sparks the electrolysis, separating water into oxygen and hydrogen. During electrolysis, the nickel sulfide evolves into a negatively charged layer that protects the anode.
Without the negatively charged coating, the anode only works for around 12 hours in seawater, according to Michael Kenney, a Stanford graduate student and the paper’s co-lead author. “The whole electrode falls apart into a crumble,” Kenney says. “But with this layer, it is able to go more than a thousand hours.”
Previous studies attempting to split seawater for hydrogen fuel had run low amounts of electric current, because corrosion occurs at higher currents. However, in this study, they were able to conduct up to 10 times more electricity through their multi-layer device, which helps it generate hydrogen from seawater at a faster rate.
The team members conducted most of their tests in controlled laboratory conditions, where they could regulate the amount of electricity entering the system. But they also designed a solar-powered demonstration machine that produced hydrogen and oxygen gas from seawater collected from San Francisco Bay.
Without the risk of corrosion from salts, the device matched current technologies that use purified water. “The impressive thing about this study was that we were able to operate at electrical currents that are the same as what is used in industry today,” Kenney says.
The researchers say they have shown proof-of-concept with a demo, but will leave it up to manufacturers to scale and mass produce the design.
Source: Stanford University, www.stanford.edu