Sustainable Photovoltaic-Powered Series Electrochemical Reactors Using Nonactive Electrocatalytic Materials for Electro-Refinery in Organics and Energy Production

The applicability of an electrochemical device with a series design and configuration, powered by photovoltaic panels, was tested as an integrated-hybrid approach for energy-efficient electrochemical green H₂ production coupled with dye effluent upgrading. This electrochemical strategy investigated the electroconversion efficiencies of a model organic compound into carboxylic acids by applying 15, 30, and 45 mA cm^-2, with simultaneous production of green H₂. Fluorine-doped lead oxide (PbO₂-F) and boron-doped diamond (BDD) electrodes were used as anodes in a three-compartment flow reactor, in series mode with different anodic order: setting 1 (PbO₂-F + BDD) and setting 2 (BDD + PbO₂-F). PbO₂-F was successfully prepared using the electrodeposition method, and it was characterized. The results clearly showed that configuration 1 (PbO₂-F + BDD) consumed 10.47 kWh m^-3 after 120 min of electrolysis by applying 45 mA cm^-2, achieving 42.5% organic removal efficiency and producing simultaneously 0.7 L of green H₂. Meanwhile, the configuration 2 (BDD + PbO₂-F) consumed 16.18 kWh m^-3 under the same operating conditions, achieving 47.5% organic load removal and producing 0.75 L of green H₂. Discoloration of the effluent was efficiently achieved in all cases. Carboxylic acid production was monitored over time at different conditions tested. Notably, a selective production of malonic acid (28% conversion efficiency) was attained using setting 1, and consequently, upgrading the electro-refinery concept using wastewater residues.