UK team produces hydrogen from fescue grass via photocatalytic reforming
21 July 2016
A team of researchers from the UK’s Cardiff University’s Cardiff Catalysis Institute and Queen’s University Belfast have shown that significant amounts of hydrogen can be unlocked from fescue grass—without significant pre-treatment—using sunlight and a metal-loaded titania photocatalyst. An open access paper on their work is published in Proceedings of the Royal Society A.
Based on their study, the team proposed that the first step in their photoreforming of cellulose was the (photo)hydrolysis of cellulose into glucose, with the latter then undergoing reforming to hydrogen and CO2. It is the first time that this method has been demonstrated and could potentially lead to a sustainable way of producing hydrogen.
Importantly, it is shown that not only precious metals such as Pt, Pd and Au can be used as the metal component, but also much more economic and less environmentally damaging Ni is effective. Even more importantly, we show for the first time, to the best our knowledge, that fescue grass as raw biomass can be effective for hydrogen production without significant pre-treatment. This provides additional benefits for the efficiency of biomass hydrogen production, because fewer processing steps for the raw material are required than in the production of purer forms of cellulose, for example.
—Caravaca et al.
The basic approach of photocatalytic reforming (or photoreforming) is to use solar energy for the activation of the catalysts involved in the reforming of the feedstocks. The aim of the UK work was to study the conversion of cellulose into hydrogen by means of the photoreforming reaction, using cellulose as the sacrificial agent.
They explored the photoreforming of cellulose over M/TiO2 catalysts (M = Pd, Au, Ni). Nickel was of particular interest to the researchers, from a practical point of view, as it is a much more earth-abundant metal than the precious metals, and is more economical.
In the first round of experiments, the researchers combined the three catalysts with cellulose in a round bottom flask and subjected the mixture to light from a desk lamp. At 30 minutes intervals the researchers collected gas samples from the mixture and analysed it to see how much hydrogen was being produced.
To test the practical applications of this reaction, the researchers repeated the experiment with fescue grass, which was obtained from a domestic garden.
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| Hydrogen evolution from photocatalytic reforming of grass and comparison with photocatalytic reforming of cellulose and photocatalytic water-splitting. Pre-treatment of grass: washing at 55°C with H2O and then with methanol, and drying overnight at 120°C. Reaction conditions: 0.36 g of washed and dried grass per 200 ml H2O, 150 mg 0.2% Pt/TiO2, temperature = 60°C. Caravaca et al. Click to enlarge. |
Up until recently, the production of hydrogen from cellulose by means of photocatalysis has not been extensively studied. Our results show that significant amounts of hydrogen can be produced using this method with the help of a bit of sunlight and a cheap catalyst.
Furthermore, we’ve demonstrated the effectiveness of the process using real grass taken from a garden. To the best of our knowledge, this is the first time that this kind of raw biomass has been used to produce hydrogen in this way. This is significant as it avoids the need to separate and purify cellulose from a sample, which can be both arduous and costly.
—Professor Michael Bowker
Resources
A. Caravaca, W. Jones, C. Hardacre, M. Bowker (2016) “H2 production by the photocatalytic reforming of cellulose and raw biomass using Ni, Pd, Pt and Au on titania,” Proc. R. Soc. A doi: 10.1098/rspa.2016.0054
If they succeed in producing hydrogen at low cost, then i might be interrested to buy a bi-fuel ice car hydrogen-gasoline mixed into the piston combustion chamber. I want to avoid the high cost of a hydrogen fuelcell car. Also with this hydrogen, make synthetic gasoline because with their process they get hydrogen and co2 and if you reform it you get synthetic gasoline and diesel and then sale that at a lower price than actual gasoline for my car.
Posted by: gorr | 21 July 2016 at 10:50 AM
A fraction of 1 cm³ of gas produced per 315 ml flask in 2 hours. Unless the reaction rate can be increased a few orders of magnitude I don't see this being worthwhile.
Posted by: Engineer-Poet | 21 July 2016 at 01:38 PM
I agree EP.
I doubt this will ever reach significant reaction rates, since it is limitted by the surface (2D) where the light can be captured, and by the amount of fotons reaching this surface.
The catalists may however have value for hydropyrolysis, which works in the bulk (3D) of the biomass.
The nature of the chemical reaction (grass + H2O --> H2 + CO2) in both strategies is equal, but 3D almost always beats 2D, especially when the real action is at nanometer scale.
Posted by: Alain | 23 July 2016 at 06:23 AM
Isn't that fraction of a CC just a byproduct of the photoreforming of cellulose in the grass to glucose? A good way to convert cellulose to glucose would be a big deal. I may be missing something, however, because the mention of subsequently converting the glucose to hydrogen and CO2 doesn't fit. Normally glucose is fermented into CO2 and ethanol. I don't know, offhand, of any easy process to go from glucose to CO2 and hydrogen, even though it's theoretically possible.
Posted by: Silverthorn | 24 July 2016 at 01:18 AM