The dream of an economy where hydrogen replaces fossil fuels for transport and energy storage looks closer to reality with the discovery that magnetic fields can enhance the production of the gas from water. The findings could lead to the replacement of expensive catalysts and other exotic solutions, changing the economics of turning water into fuel.
Hydrogen is an energy-dense fuel that produces nothing but water when burned, avoiding both the air pollution and climate consequences of existing fuels. Yet three things are needed for its widespread use: cheap sources of clean energy to split water, an efficient mechanism for the splitting, and safe and affordable ways to store and move the gas once made.
The plunging price of solar power in sunny places is offering us the first. The most efficient methods available for the second, however, rely on catalysts using “noble” metals such as platinum or iridium. Since platinum is famously more expensive than gold, and iridium so rare its presence serves as a marker of asteroids, the problems are obvious. Even though the definition of a catalyst is not to be consumed in the chemical reaction it stimulates, the cost of noble metals does not justify the hydrogen they can produce.
In the search to improve the efficiency of cheaper options, Dr Felipe Garcés-Pineda of the Institute of Chemical Research of Catalonia has found magnetic fields can help when at least the catalyst itself is magnetic. Catalysts made of the magnetic metals iron or nickel, whose costs are a fraction of the noble metals, exist for water splitting but are currently inefficient and produce hydrogen at low rates. “The simplicity ...[and] low cost of the technology makes it suitable for industrial applications," Garcés-Pineda said in a statement.
In Nature Energy, Garcés-Pineda has announced a variety of low-cost catalysts made partly from nickel or iron that performed at least 10 percent better in an applied magnetic field.
The most dramatic effect among the materials Garcés-Pineda tried was with NiZnFe4Ox, where hydrogen production more than doubled when the magnetic field was turned on. All four elemental components are common and in widespread use, so the cost of the catalyst is tiny compared to platinum and its relatives. As an added bonus, the magnetic field causes the catalyst to attach to a nickel subsheet, rather than requiring the adhesives. Nickel-foam electrodes, seen as a great hope for hydrogen production, were 40 percent more efficient in a magnetic field.
The experiments were done in fields of less than 450 milleteslas, 10,000 times stronger than the Earth's magnetic field but nothing extraordinary by laboratory standards.
The technique appears to work because it aligns the electron spin of the oxygen molecules released as the water is split. Formation of the oxygen-oxygen bond is currently the bottleneck for hydrogen production since if O2 does not form, the leftover oxygen prevents hydrogen's release.