Low Pd loadings onto Printex L6: Synthesis, characterization and performance towards H₂O₂ generation for electrochemical water treatment technologies

In order to enhance hydrogen peroxide (H₂O₂) electrogeneration, a catalyst based on less than 1 wt% of Pd nanoparticles dispersed onto commercially available Printex L6 carbon black (PCL6) is proposed and synthetized. The material was characterized by physico-chemical and electroanalytical methods, demonstrating high activity with a 320 mV lower onset potential compared to pristine PCL6 and high stability after 5000 potential cycles. Its performance places it among the most efficient bi- and monometallic electrocatalysts for H₂O₂ production. When testing the accumulation of H₂O₂, a 1.69-fold molar increase was observed for Pd_1%/PCL6 compared to PCL6. Different electrochemical advanced oxidation processes based on H₂O₂ generation have been performed to oxidize and remove pollutants as exemplarily shown on methyl paraben in Na₂SO₄ solution as model pollutant. A boron-doped diamond electrode was used as anode while Pd_1%/PCL6 was tested in a rotating ring disk electrode (RRDE) and gas diffusion setup. Pollutant degradation followed a pseudo-first-order reaction kinetic in the following order: anodic oxidation along with H₂O₂ generation (AO-H₂O₂) < AO-H₂O₂/UVC < electro-Fenton (EF) < photoelectro-Fenton (PEF). The best mineralization performance was found for PEF due to the photodecarboxylation of Fe (III) complexes with UVC light, while the process with lowest energy consumption per order was EF with 0.488 kWh m⁻³ order⁻¹. At the end of the work a route for pollutant mineralization was suggested.