In the upcoming highly electrified energy scenarios, electrolysis technologies are the new industrial paradigm. In particular, electrochemical hydrogen production or carbon dioxide electroreduction are becoming a key technology to achieve climate neutrality. For this kind of electrolysers, recent studies have pointed out the need to replace the sluggish anodic oxygen evolution reaction (OER) by alternative reactions that allow reducing the required overpotential that currently limits their economic feasibility. The oxidation of low value biomass-derived alcohols like glycerol is foreseen as an interesting approach, since alcohols can be partially oxidized to value-added products and, in case of complete mineralization, their associated CO₂ emissions are considered neutral.

Most of the studies on the electrochemical glycerol oxidation reaction (GOR) with non-noble metal catalysts in alkaline media have been focused on nickel- and cobalt-based oxides, hydroxides or oxyhydroxides, with a lack of comparative study. The aim of this work is to discern whether the raw hydroxide or the promoted oxide form of a Ni-Co LDH as precursor of a spinel structure is the most suitable electrocatalyst for glycerol oxidation in alkaline medium. Ni:Co electrocatalysts with atomic ratios of 2:1 and 1:2 were synthesized on NF cathodes, were synthesized by electrodeposition from a nitrate-sulfate electrolyte that allowed obtaining two different LDHs, whose thermal treatment at 300 ºC caused a mass loss attributed to the removal of compensating anions present in the LDHs. The two untreated and two thermally-treated electrodes were characterized by cyclic voltammetry and linear sweep voltammetry in alkaline medium, in the presence and absence of glycerol. The results showed that in these two cases, the onset potential for the metal hydroxide electrocatalyst oxidation was the same. Regarding the GOR, it was mediated by the resulting oxyhydroxide, and the presence of a greater nickel content as well as the application of the thermal treatment led to a higher anode polarization, which is detrimental in terms of energy need. A potential difference of 0.2 V was determined when comparing the water and glycerol oxidation voltammograms at 25 mA cm^-2, which may exert a positive impact of up to 15% on the energy requirement for electrolytic hydrogen production. Galvanostatic electrolytic trials showed that formate ion was the primary product, with an FE often higher than 70%. It was found that the hydroxide samples suffer from electrode potential oscillations that may restrict the glycerol conversion. Thermally-treated coatings appeared to show higher stability upon repeated usage, although the actual long-term stability should be studied with more detail in a focused work. Regarding the Ni:Co ratio, the best proportion has not been clearly elucidated but, in all cases, the TT had a more relevant role as it improved the FE to formate as well as the overall glycerol conversion.