Water splitting is an emerging technology for hydrogen fuel cells. Two semiconducting electrodes are connected and placed in water. The electrodes absorb light and use the energy to split the water into oxygen and hydrogen. The oxygen is released into the atmosphere, and the hydrogen is stored as fuel. The hydrogen can later be recombined with oxygen to produce energy with byproduct of just water.
The entire process is sustainable and clean. But finding a cheap way to split water has been a major challenge. Today, researchers continue searching for inexpensive materials that can be used to build water splitters efficient enough to be of practical use.
Scientists from Stanford University, California, have created a low-cost and corrosion-free water splitter using nickel-coated silicon electrode to absorb sunlight to generate hydrogen. "Silicon, which is widely used in solar cells, would be an ideal, low-cost material," said Stanford graduate student Michael J. Kenney, co-lead author of the study. "But silicon degrades in contact with an electrolyte solution. In fact, a submerged electrode made of silicon corrodes as soon as the water-splitting reaction starts."
To find a low-cost alternative, the team tried to coat silicon electrode with a 2 nanometer think ordinary nickel. "Nickel is corrosion-resistant," Kenney said. "It's also an active oxygen-producing catalyst, and it's earth-abundant. That makes it very attractive for this type of application."
When light and electricity were applied, the electrodes began splitting the water into oxygen and hydrogen, a process that continued for about 24 hours with no sign of corrosion. To improve performance, they mixed lithium into the water-based solution. "Remarkably, adding lithium imparted superior stability to the electrodes," Kenney said. "They generated hydrogen and oxygen continuously for 80 hours – more than three days – with no sign of surface corrosion." This was one of the longest lasting silicon-based photoanodes for water splitter,
The team plans to do additional work on improving the stability and durability of nickel-treated electrodes of silicon as well as other materials.