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.
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
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