EPFL team discovers molybdenum-based catalysts enable more cost-effective hydrogen production from water
15 April 2011
A team led by Ecole Polytechnique Fédérale de Lausanne (EPFL) Professor Xile Hu has discovered that a molybdenum-based catalyst allows the electrolytic production of hydrogen at room temperature, and is inexpensive and efficient. The results provide new opportunities for the development of renewable and economic hydrogen production technologies. A paper on the work appears in the RSC journal Chemical Science.
Water splitting for hydrogen production consists of two half cell reactions; the hydrogen evolution reaction requires catalysts. While nickel-based catalysts are often employed in commercial alkaline electrolyzers, platinum and its composites are the most active catalysts for hydrogen evolution in an acidic medium, Hu et al. note. The large scale application of Pt catalysts is limited by their high cost and low abundance.
Extensive efforts have been devoted to the search of alternative catalysts containing only non-precious elements under heterogeneous conditions. Yet functional and robust catalysts operating with reasonable current densities (J) at low overpotentials (η) in water are scarce.
Recently, MoS2 nanoparticles have been identified as promising hydrogen evolution catalysts. Bulk MoS2 is a poor catalyst; nano-crystals of MoS2 and related metal sulfides, however, are more active...Notwithstanding the impressive advances, the practical implementation of these systems is hindered by their sophisticated and/or energy intensive preparation procedures, such as ultra-high vacuum conditions, reduction by H2S streams and annealing at elevated temperatures.
Here we report that amorphous molybdenum sulfide films are active hydrogen evolution catalysts. The catalysts are prepared at room temperature and atmospheric pressure, and in a simple, rapid, and scalable manner. Furthermore, compared to MoS2 nanoparticles, the amorphous molybdenum sulfide films exhibit higher activity.
—Hu et al.
In their study, Hu et al. explored four different molybdenum sulfide films. The new catalysts exhibit many advantageous technical characteristics. They are stable and compatible with acidic, neutral or basic conditions in water. The study found that these amorphous molybdenum sulfide films are among the most active non-precious hydrogen evolution catalysts.
In their study, they found that significant geometric current densities are achieved at low overpotentials (e.g., 15 mA cm-2 at η = 200 mV) using these catalysts. The catalysis is compatible with a wide range of pHs (e.g., 0 to 13). The current efficiency for hydrogen production is quantitative. A 40 mV Tafel slope is observed, suggesting a rate-determining ion+atom step.
It was only by chance that the team made this discovery during an electrochemical experiment.
It’s a perfect illustration of the famous serendipity principle in fundamental research. Thanks to this unexpected result, we’ve revealed a unique phenomenon, but we don’t yet know exactly why the catalysts are so efficient.
—Xile Hu
Further characterization and application of the catalyst, such as further stability studies and impedance analysis are currently underway.
Resources
Daniel Merki, Stéphane Fierro, Heron Vrubel and Xile Hu (2011) Amorphous Molybdenum Sulfide Films as Catalysts for Electrochemical Hydrogen Production in Water. Chemical Science doi: 10.1039/C1SC00117E
Producing Hydrogen with less energy at lower cost could make it one of the favored energy storage medium and fuel in the future. Small production units at filling stations could solve the distribution problem.
Posted by: HarveyD | 15 April 2011 at 08:12 AM
The sad part is that this will spur a rash of unrelated posts from the nut-jobs who will now claim they can use this to run a car on water alone! It's FREE energy folks, it grows on trees! LOL
Posted by: DaveD | 15 April 2011 at 09:49 AM
What is the precise meaning of "efficient" in this case?
Does that mean that now only 45% of the energy is lost during conversion to H2?
Does that mean that 50% of the energy is lost, but with much cheaper catalysts?
I guess having a cheaper catalyst allows them to continue tweaking the process to reduce conversion losses, but the fundamental physics may be that conversion losses will always be high and greatly favor battery storage of energy.
Posted by: HealthyBreeze | 15 April 2011 at 11:16 AM
This technology should be seized by the military to help fight the war on terror. Then after the war it could be privatized to ensure the government does not misuse it and make it cost 10 times more with unionized bureaucratic waste. The free market can find the solution if you let it. Government regulations are not actual solutions.
Posted by: Paris Palin | 15 April 2011 at 12:54 PM
If the private sector was the holy grail, we should have seen results long ago.
Posted by: SJC | 15 April 2011 at 06:03 PM
Don't forget that private industries require a 20% to 22% yearly profit margin, tax credits and be exempt from law suits before they are interested.
Since their requirements are so high, couldn't governments join in (at 30% or 40%) and benefit too?
Posted by: HarveyD | 17 April 2011 at 10:01 AM
That seems to be the on going story, just give them more deregulation and larger tax breaks and things will be fine.
In the 1950s corporations paid 40% of the federal budget and the highest tax bracket was 91%. This was a time of NO budget deficits and prosperity for the middle class.
Posted by: SJC | 17 April 2011 at 06:09 PM
Can we stick to the technical issues and leave the liberal agenda a the door. Someone please shed some more light on the energy efficiecy questions Healthy posed. Also I have pondered the practicality of pumping water into a vessel (at H storage pressures) and then electrolizing while maintaining that pressure. This could improve the energy efficiency and economics (pumps are cheaper then compressors) of the storage issue.
Posted by: Tim Duncan | 28 April 2011 at 05:58 PM