Electro-Reforming of Biomass Gasification Tar with Simultaneous Hydrogen Evolution

In this study, an electrochemical valorization strategy on liquid byproducts from hazel-nut shell gasification was developed to couple waste remediation with energy-efficient hydrogen production. The aqueous phase, rich in organic compounds, is processed in an anion exchange membrane (AEM) cell, where pure hydrogen evolved at the cathode while organic pollutants are oxidized at the anode. First, the feedstock is thoroughly charac-terized using gas chromatography-mass spectrometry (GC-MS), identifying a complex matrix of water-soluble aromatic compounds such as phenols, catechols, and other aro-matics compounds, with concentrations reaching up to 2.9 g/kg for catechols. Then, the electro-reforming process is optimized using Nickel oxide-hydroxide (Ni(O)OH) elec-trodes with a loading of 0.75 mg/cm2. This methodology relies on the favorable thermo-dynamics of organic oxidation, which requires a lower onset potential (0.4 V) compared to the oxygen evolution reaction (OER) observed in the alkaline control (0.52 V), and the low overpotential of the Nickel oxide-hydroxide electrode towards the oxidized species. Consequently, the organic load undergoes progressive oxidation into hydrophilic and less bioaccumulating species and carbon dioxide, allowing for the simultaneous genera-tion of pure hydrogen at the cathode at a reduced cell voltage. Elevated stability was observed, with a substantial abatement of organic compounds achieved over 80 hours at a fixed cell voltage of 0.5 V. This represents a step forward in the development of tech-nologies that reduces the energy intensity of hydrogen generation while valorizing bio-mass gasification residues.