Biomass-assisted water electrolysis

Water electrolysis consists in breaking the water molecule into hydrogen and oxygen. $\left({\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_2+\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.{\mathrm{O}}_{\mathrm{2}}\right)$ under the effect of an electrical voltage. However, the water molecule is thermodynamically very stable, and the energy required to break it down is very high, which translates into a very high electrolysis cell voltage. The cost of hydrogen production is directly linked to the electrical energy consumed, and therefore to the cell voltage.

Thermodynamic data show that the electrooxidation of oxygenated organic molecules generally takes place at much lower potentials than those required for water oxidation, and their use in an electrolysis cell could therefore reduce the energy required for hydrogen production by a factor of at least two.

Among oxygenated organic molecules, compounds derived from lignocellulosic biomass waste (glucose, fructose, furanic compounds, etc.) are renewable and do not compete with human or animal foodstuffs. The controlled electrooxidation of glucose, for example, into (di)carboxylic acids in an electrolysis cell yields industrially important synthons for the development of biobased monomers and surfactants for applications in the bioplastics and bionyls, cosmetics, detergents, cement industries, etc. The hydrogen produced at the cathode can be valorized on site in a biorefinery by using it to carry out lignin hydrodeoxygenation reactions to produce biofuels, or reductive amination reactions to produce biobased surfactants, or can be stored and subsequently used to produce energy in a fuel cell.

However, to achieve the conversion rates and selectivity needed to deploy this technology in a biorefinery, it is necessary to develop suitable catalytic materials.