3D printed bimetallic electrodes for optimized electrochemical oxidation from batch to flow cell: A multiscale study

This work investigates 3D-printed monometallic (Ni) and bimetallic (NiCo) electrocatalysts fabricated via Direct Ink Writing (DIW) and systematically evaluates their performance in a model electrochemical oxidation reaction, in both batch and flow configurations. The selected reaction, electrochemical conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), the building block of bio-based plastics, is an attractive process that leverages renewable electrons and carbon resources. The process offers the potential to increase energy and cost efficiency by combining mild reaction conditions with high activity. Despite extensive research on nickel-based catalysts, the use of 3D-printed bimetallic electrodes for this type of reactions has never been reported. Chronoamperometric experiments performed at 1.8-2.2 V with 50–200 mM HMF demonstrated that electrodes prepared from fine powders (1.6- 7 μ m ) exhibit superior activity compared to those based on the coarse powders ( 44 μ m ), while the electrode composed of NiCo powders in [50:50] weight percentage ratio delivered the best overall performance among the bimetallic systems. When implemented in a parallel-plate flow reactor, both the electrodes composed of fine Ni and Co powders in [75:25] ratio and the electrode composed of coarse NiCo powders in [50:50] ratio achieved complete HMF conversion and a 95% FDCA yield within 60 min, outperforming the batch configuration. Alongside SEM and EDS characterisation, XRD-CT slices were collected at different heights throughout the electrode providing further evidence on microstructure and phase distribution before and after HMF oxidation.