Credit: Delft University of Technology
Hydrogen has the potential of becoming one of the replacements for fossil fuels as an energy carrier in the not-so-distant future. It is clean, as heat and water vapor are the only by-products of combustion. Plenty of it can be produced using just water and another energy source (for instance solar energy).
But the fact remains that it can also be dangerous, as it is combustible and hard to detect. To be able to use hydrogen safely, sensors that can detect even the slightest of leaks are needed. A team of researchers from
TU Delft, KU Leuven and the Rutherford Appleton Laboratory (UK) have found out that the metal hafnium is ideal solution.
Optical sensors can be utilized to detect hydrogen. These are materials that absorb hydrogen atoms, a process that changes their reflectivity. This modification in reflectivity can be measured, thus giving information regarding the amount of hydrogen in a specific location.
Until now, pure palladium was mainly used as an optical hydrogen sensor. But over the last few years, we at Delft have shown that a gold-palladium alloy is a much better sensor. Fellow-researchers around the world are also studying this.’
Prof. Bernard Dam, TU Delft
Palladium-gold, which is also used to design jewelry, has the benefit that it works at room temperature. Unfortunately, it is incapable of detecting low hydrogen pressures.
Easy to calibrate
Research guided by PhD candidate Christiaan Boelsma from TU Delft, which has recently been published in Nature Communications, reveals that Hafnium does possess this sensitivity.
The unique property of this material is that it can optically measure a minimum of six orders of magnitude in pressure. The lowest pressure measured is 10-7 atmosphere, but this pressure is determined by the measurement set-up. It looks as if a pressure of three orders of magnitude lower could be measured with hafnium, but we need to do more research to confirm this.
Prof. Bernard Dam , TU Delft
Another advantage is that the optical properties of hafnium alter linearly with the temperature and pressure of the material.
This makes hafnium sensors very easy to calibrate.
Prof. Bernard Dam , TU Delft
Compared to palladium-gold, is hafnium then a better hydrogen sensor in all aspects? No, because this materials ideally requires a temperature of approximately 120 °C to work. Dam believes that this issue can be solved by depositing a thin layer of hafnium on top of an optical fiber, before heating the fiber with a warm-up LED.
Delft is presently conducting widespread research into hydrogen. Late last year, Prof. Fokko Mulder introduced the ‘Battolyser’, a device that integrates electricity storage and hydrogen production into a single system. The Battolyser is an economical way of producing and storing hydrogen, and brings the so-called ‘hydrogen economy’ one step closer. This study into sensitive hydrogen sensors signifies another step in the same direction.